MCU14/0024 - Response to Information Request - Attachment 4

Page 2

1 INTRODUCTION

SCG Consulting Engineers has performed a site classification in accordance with AS 2870-2011 and made
recommendations based upon the ciassification for a buiiding to be constructed ai the above site. This
report does not include an assessment of Slope Stability, Landslide Risk, or specifications for damp proofing,

termite protection or moisture barriers.

  

This soil test and footing report relates only to the above property and the proposed construction as
described below:

 

Proposed Construction

Residential Dwelling

 

 

 

 

 

External Walls Masonry
Internal Walls Timber/Masonry
Ground Floor Slab on Ground
Upper Fioor Suspended Slab
Building Platform Cut Fill Pad

 

Masonry Articulation

 

Required @ 8 m centres

 

 

 

 

This report must be read and considered as a whole. All of our recommendations,
foundation plans, sections and appendices must be read, considered and followed by all
people involved in this project including the client to ensure adequate long term
performance of the footing system constructed on this site. A copy of this report must
remain with the client or final owner of the building upon completion of the
proposed works. If you are unsure of any of the requirements herein, you must seek
clarification from this office.

2 SITE CLASSIFICATION

After considering the results of our field investigation performed on 06/01/2014 we have classified this site in

accordance with AS 2870-2011 as:
[_ ClassP |

The classification has been calculated from test work performed on the soil profile encountered on the day of
our fieldwork and consideration of AS2870-2011. Any disturbance of the soil profile may result in a change
to the classification.

 

The ‘P’ classification relates to the loose sands and poor bearing capacity encountered during our testing on
site. Please refer to our definitions list appended to this report for further descriptions of these
characteristics.

With respect to potential surface movements through seasonal moisture variations, the site could be
considered equivalent to a class S site.

The site preparation details that follow have allowed for the influence of the earthworks described in section
5.0 below.

Site Classification: The site classification is calculated in accordance with the “AS2870-2011 Residential
Slabs and Footings-Construction” and relates to the estimation of Ys, “The characteristic surface movement”
within reactive soil profiles. The limits used for this classification are as follows:

 

 

 

 

 

 

 

 

 

 

 

 

[ Predicted Surface Movement _[ Classification |

Ys = <=20mm $s Slight

Ys = >20 - 40mm M Moderate
Ys = >40 —- 60mm H1 High-1

Ys = 60 — 75mm H2 High-2

Ys => 75mm E Extreme

Problem sites P Problem

SCG Consulting Engineers 1 SCG Ref: 23277(S)

 

Page 3

3 SITE DESCRIPTION

The construction area has a gradient in the order of 26%.

Vegetation on the construction area (and nearby surrounds) consists of scattered trees.
The trees are located on and adjacent the proposed construction site.

The trees are of a height and proximity that could affect the moisture conditions within the proposed
construction site. Refer to the appendices to the rear of this report for guidance on Trees and Construction.

The existing surface drainage is good and sub-surface drainage is good.

4 FINDINGS

The soil profiles encountered are shown on the attached borelog sections.

No water table was encountered during our testing program.

The sandy soils encountered are susceptible to collapse when unconfined. This may effect excavations and
result in additional earthworks and increased concrete volumes. Temporary shoring or Forma-Tube may be

required to retain the sands prior to concreting.

The samples classified on-site were assessed as having negligible plasticity, therefore laboratory testing was
considered unnecessary.

We have assessed the expected differential movement of the soil profiles encountered to be the equivalent
of a site with a Ys of less than 20mm.

For buildings within the scope of AS 2870-2011 a maximum allowable bearing pressure of 100 kPa is
available within the natural soils at the following depths:

 

[__ Test Site 1-1600mm_ _|__ Test Site 2- 1600mm |

 

The following foundation material will provide a safe bearing capacity (100 kPa) for buildings within the scope

of AS 2870-2011 and is shown shaded on the attached logs;

FOUNDATION MATERIAL - NATURAL MEDIUM DENSE SILTY SAND

5 SITE PREPARATION DETAILS

We recommend scraping this site free of all organic material and debris. The proposed construction areas
should then be cut and filled for the construction of a block base. The bases must be filled with a clean
material from the cut. The fill is to be free of organic material and have no clay content. In areas where the
excavator cannot access the fill is to be wetted and compacted in 150mm layers with a vibrating plate
making 6 passes (3 in each di ection). Temporary back Propping to the block base should be provided
throughout the compaction process. The fill is to be placed and compacted in accordance with AS3798-2007
to a level sufficient to achieve a Level 1 certification with a minimum relative field density of 95%. Copies of
compaction test results shall be presented to SCG Consulting Engineers for approval.

 

   

Where a retaining wall is required, a cut batter of 1 to 2 (vertical to horizontal) in the sand profile taken from
the base of the proposed wall should be excavated. These earthworks must incorporate shallow surface
spoon drains at the base and along the high side of the cut. Drains must have an efficient outflow down-
slope and clear of the construction area. The exposed face should also be protected against the potential for
stormwater erosion. Should these recommendations be un-achievable the builder should seek guidance
from this office on temporary shoring, benching or other suitable techniques.

SCG Consulting Engineers 2 SCG Ref: 23277(S)

Page 4

Areas where existing structures or trees are removed shall be backfilled with engineer approved fill material
compacted to achieve a minimum relative field density of 95% and be in accordance with AS2870-2011.
Where trees are removed prior to construction the moisture conditions of the soils must be allowed to
normalise across the site prior to commencing foundation preparations.

Any loose or soft material uncovered in the site preparation shall be removed and replaced with approved fill
material compacted in accordance with AS2870-2011, or alternative measures to be provided by the
engineer.

We recommend using a footing system as per the attached plans and details on the prepared construction
pad.

For the design to be valid the cut/fill line must be in the position shown on our footing plan. Any variation
must be brought to the attention of this office before continuing work.

Site drainage during construction is important. Stormwater run-off should be diverted away from any
foundation excavations and not be able to pond within 5.0m of the building footprint. Temporary piping or
spoon drains or other practical methods should be used. Please refer to the Appendices to the rear of this
report for drainage management.

The final surface profile should fall away from any slab on ground for a minimum of 1.5m at a grade of no
less than 1 in 20. Refer to appendices for drainage recommendations.

Where site drainage and landscaping does not conform to the specifications of AS 2870-2011 and CSIRO
Information Service Sheet BTF-18 significant damage to the building can be expected. A single copy of this
document is issued with the original issue of this report. Please consult your builder or contact this office to
obtain a copy.

The builder must ensure the stability of neighbouring/existing structures is maintained through not
undermining their foundations. This is achieved via restricting any excavations to above a line
radiating downwards at an angle of 4 in 1.5 (vertical to horizontal) from the base of the
foundation/structure to be protected.

 

Any new vegetation including trees planted adjacent the structure should follow the recommendations
appended to this report.

6 FOOTING AND SLAB SPECIFICATIONS

Footing Details

All footings must be founded a minimum of 300mm into the NATURAL MEDIUM DENSE SILTY SAND (shown
shaded on the attached log sections). Dimensions and reinforcement requirements are detailed on the
structural plans and details.

Where the NATURAL MEDIUM DENSE SILTY SAND is deep or is covered by the introduction of fill, the footings
are to be increased in depth to reach this level. Alternatively the footings can be supported on piers founded
at or below the founding level. Refer to the structural plans for details.

Drilled Piers Supporting the Footings

Where the NATURAL MEDIUM DENSE SILTY SAND is deep or to be covered by fill the footings can be
supported on drilled concrete filled piers founded at a minimum of 300mm into the NATURAL MEDIUM DENSE
SILTY SAND. The size and spacing of these piers is nominated on the structural plans.

Where drilling piers is not practical the footings could be supported on steel screw piers.

Floor Slab Details

The thickness and reinforcement for slabs on ground are shown on the structural plans.

SCG Consulting Engineers 3 SCG Ref: 23277(S)

Page 5

Ground slabs may require thickenings or stiffening beams incorporated in their construction. It may be
advantageous to excavate them at the same time as the perimeter footings. Refer to the structural plans for
the locations and extent of these.

Where the stiffening beams intersect a perimeter footing, their base must be graded down to the footing
base level, 3 x N12 bars must be cogged into the footing and lapped 500 with the beams trench mesh.

Refer to the structural plans for details.

 

Where the stiffening beams intersect a block base or retai ing wall, 3-N12 bars must be dowelled 150mm
into the blockbase and lapped 500 with the beams trench mesh. Refer to the structural plans for details.

A levelling layer under the ground floor slab is to comprise of granular material such as clean sand or
crusher dust compacted in 150mm layers. Either well graded sand or crusher dust can be used.

An approved polyethylene damp proof membrane of 0.2mm (min) thickness is to be placed over the levelling
layer. Laps are to be a minimum of 200mm and be taped. All service penetrations and punctures are to be
fully taped. The membrane is to be extended down the inside face of the perimeter footings and must
continue under any thickenings or stiffening beams.

Drilled Piers Supporting the Stab

Slab piers are required where there is more than 300mm of uncontrolled fill beneath the slab. They are to be
founded at a minimum of 300mm into the NATURAL MEDIUM DENSE SILTY SAND. Special attention must be
paid to the extra slab thickening required over slab piers as detailed in the structural plans.

Where drilled piers supporting columns or posts are not poured with the slab they must be connected to the
slab in the following manner:

e 4-N12 bars must be anchored 500mm into the drilled pier and be bent 300mm horizontally into the
footing or slab as required.

e Where a column penetrates a beam or footing 3-N12 bars must be bent around the column to lap the
trench mesh by 500mm both sides.

Drilled Pier Reinforcement

 

 

 

 

 

 

[_ Pier Depthmm | Perimeter Piers | Slab Piers _|
up to 1500 None required none required
1500-2500 2xN12bars none required
2500-4000 4xN12bars 2xN12bars
4000-6000 6xN12 bars 4xN12bars

 

 

 

 

 

Pad Footing Details

All pad footings must be founded to the depth nominated on the structural plans. Where this depth is not
300mm into the NATURAL MEDIUM DENSE SILTY SAND they must be deepened down to this level.

NOTE: The information contained herein has been compiled following our field and laboratory
testing, accepted engineering theory and discussions with and information supplied by our
client, whom is noted on the header page of this report. We offer no warranty for the use of
this report by other parties without prior written consent from this office.

The regort must be read in conjunction with the attached appendices. If you do not have a
copy ese please contact our office and a copy can be issued to you.

   

for and on behal

SCG Consulting Engineers 1 SCG Ref: 23277(S)

Page 6

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Page 7

APPENDICES

 

A
B.
c
D

DEFINITIONS
LIMITATIONS

CONSTRUCTION NOTES
RECOMMENDATIONS

D.1- Builders

D.2- Owners

D.3 - Builder/Owner - Trees

DETAIL SHEETS

E.1 - Plumbing Requirements Class M, H1, H2 & E Sites
E.2 - Site Drainage recommendations
SITE PLAN

BORELOGS

Page 8

A. DEFINITIONS

Safe Bearing capacity: The si nominated in this report as a suitable foundation material has an allowable bearing capacity of 100KPa
and is considered safe for the construction of a dwelling that is in accordance with AS2870-2011.

 

Cohesive Soils: Clays and silt soils that nave innerent coh i ding} strength.

 

Granular Soils: Gravels and sand soils that have no cohesive strength. Individual particles can flow under certain conditions.

Controlfed Fill; Manually placed soil which has been placed and compacted to achieve sufficient bearing capacity to support a structure
according to AS 2870-2011. Fill certified at Level 1 according to AS 3798 and 95% Relative Field Density is considered controlled fill.

Partially Controlled: Manually placed soil which appears to have been compacted under controlled conditions but, at the time of preparing
this report, no compaction certificate suitable for compliance to Level 1 of AS 3798-2007 had been presented.

  

Uncontrolled Fill: Manually placed soil (overlying the natural soils) which is not adequate to support a normally loaded footing or floor slab

or structural load.

Unexcavatable Rock: Strong material that does not soften in water or collapse under the combination of loading and wetting. Material that
cannot readily be excavated by a backhoe.

Excavatable Rock: A rock-like material including shaly material and strongly cemented sand or gravel which does not shrink or swell with
changes in soil moisture, but is readily excavatable with a conventional backhoe.

 

 

is defined as any wall imposing on the footing a service load greater than
our slab designs.

Load Bearing Wall: in our design work a load bearing wal
40KN/m. A load bearing wall will normally be supported by a slab thickening or footing

 

 

Natural (Strata): Refers to soil thatis neither fill or imported material but one that is in its original undisturbed state and position.

Gravel: Coarse particles, larger than sand size, but less than 60mm in diameter.

 

Cobbles: Rocks greater than 60mm in diameter but less than 660mm in diameter.

Boulders: Rocks larger than 600mm in diameter.

SOIL STRENGTH INDICATIONS

 

NON-COHESIVE (GRANULAR) SOILS COHESIVE SOILS
Loose A 12mm rod/bar can be easily pushed in by hand Soft Can be moulded by light finger pressure.
Medium A412 mm rod/bar can be pushed in 300mm with Firm Can be moulded by strong finger pressure.
Dense difficulty
Dense A 12mm rode cannot be pushed in by hand. Stiff Cannot be moulded by fingers. Can be indented by

thumb with pressure.

 

Very Stiff Can be indented only by thumb na

N.B. These indications should be used for guidance only. These indications can vary greatly under Abnormal Moisture Conditions.
Please contact SCG Consulting Engineers for on-site clarification of soil strengths.

 

B. LIMITATIONS

AS2870-2011: This report and associated foundation designs have been completed in accordance with AS2870-2011 the Australian
Standard for “Residential Slabs and Footings” design and construction. The standard provides performance based criteria for its design
recommendations. This criteria is not based upon crack or movement free performance. The code states acknowledged that minor
foundation movements occur on nearly all sites and that it is impracticable to design a footing system that will protect the building from
movement under all circumstances”. The code provides guidance on the assessment of crack sizes in walls and floors and suggests
acceptable limits. Should the potential owner not be satisfied with this criteria we should be notified such that any associated design can be
amended to suit their requirements. However, it should be noted this could dramatically increase the construction costs.

 

  

 

 

 

Field Testing: Our investigation and the results and recommendations contained herein have been compiled following careful
consideration of our clients supplied information and instructions. Such considerations include the proposed structure to be supported and
its position, proposed earthworks and land use. Any variation to this information may render this report incorrect. Furthermore this report
must not be used by any person other than our ent noted at the head of the report.

 

  

Client Supplied Information: In writing this report we have considered all the information supplied to us by the client. Should the client or
his agent have omitted to supply us with relevant information our report may be irrelevant and / or inappropriate. We do not accept
y for the consequences in such cases.

 

 

Borelogs: The soil profiles reported in our Borelogs Section represent the soil conditions at our test sites and have been located were we
believe best represents the soils within the proposed building envelope. However soil conditions can change dramatically over short
distances, therefore such point type exploration programs may not locate ali variations. if site preparations/excavations reveal si

conditions that are different from those shown in our Borelogs we must be notified immediately. Changes to the site classification and/or
footing design may be necessary.

 

Site information: The site information shown on the attached plans such as surface grades and levels are estimations taken during our
field testing and are provided for a rough guide. They must not be used for any design purposes. Site plan dimensions are as measured
from the noted visible site feature during our field testing.

Previous/Future Excavations: The recommendations contained in this report have not considered the effects of any previous, current or
future excavations, mines or slope instability problems that are not highlighted in the clients supplied information or, that was not clearly
visible during our field testing. If such features exist we must be advised so that our design can be adjusted to accommodate them.

SCG Consulting Engineers Appendix Page 20f7 Appendices.1

 

 
 

Page 9

Trees: Trees can have a considerable effect over the over the performance of a structures foundation, in particular those founded on
reactive soils (Class S, M, H & &). Their pursuit for moisture will change the moisture characteristics of the surrounding soils leading to
localised shrinking and swelling which can exceed the expected soil movement. This can include trees that have been removed prior to
construction. During our Field-testing we have considered trees that existed on or adjacent the site and allowed for them in our
recommendations/design. We are unable to allow for the potential effects trees planted after our testing, reference should be made to
“Recommendations for Butiders/Owners: Bu

 
  
 

"in Appendix B thai follows.

 

 

Moisture Conditions: The moisture conditions noted within this report are as recorded at the time of our field testing and have been
included in our assessment of the site. Changes to site drainage, the planting of trees or a rising water table can lead to increased levels of
moisture within the soils leading to either an increased classification or design requirements. We must be notified of any increase in
moisture conditions. Also refer to “Recommendations for Builders/Owners — Site Drainage in Appendix D that follows.

  

 

Aggressive/Contaminated Soils: This report does not consider the presence of contaminants or sulphates within the tested soils as this is
beyond the scope of this report and our expertise. Engagement of a specialist consultant is advised if this form of assessment is required.

Landslip: This report does not address siope stability issues. A specialist report must be obtained to assess such hazards.

Shrinkage Cracking: Shrinkage cracking of concrete occurs as the initial moisture in the concrete evaporates from mix causing
shrinkage to occur. The cracking as a result of this shrinkage is not a sign of structural failure and is to be expected in most concrete
elements poured on-site. AS2870-2011 states “Shrinkage cracking can be expected in concrete floors’. Unless requested by our client we
do not design concrete floor slabs to be shrinkage crack free.

C. CONSTRUCTION NOTES
C.1 ‘General

We strongly recommend footing excavations be inspected by a qualified person with appropriate experience to
confirm the FOUNDATION MATERIAL and proposed foundation depths are as nominated herein.

Similarly all preparations should be inspected prior to the pouring of concrete by a qualified person with
appropriate experience to confirm that the workmanship and construction conforms with the details and
recommendations contained herein and on associated documentation.

All building dimensions are to be obtained from the approved architectural plans.

 

All excavations must be totally free of all loose material and debris before pouring. They must be cleaned out so that the concrete is poured
onto undisturbed ground. Tamping and/or watering loose material is not acceptable.

Light watering of prepared surfaces is permitted prior to placing concrete.
All works must be approved by the regulatory authority prior to commencing.

C.2 ‘Tiled Areas
In areas where ceramic floor tiles or brittle coverings alike are specified for ground floor slabs we recommend increasing the size of the siab

mesh by one grade. Use flexible adhesives when affixing tiles and delay the laying for as long as possible (at least 3 months, preferably 6
months) after the stab is poured.

C.3 Concrete

Concrete for footings shall not be less than N25 (25MPa) with 20mm Aggregate and maximum slump of 80mm. Footing concrete must be
vibrated. Concrete for floor slabs shall not be less than N25 (25MPa) with 20mm Aggregate and maximum 80mm slump. Concrete slabs
greater than 100mm thick must be vibrated. In no instance shall concrete be ‘wetted up’ on site during placement.

C.4 Reinforcement

Reinforcement is to comply with the following:
a) Concrete cover to the reinforcement must be 50mm from unprotected ground, 40mm to external exposure, 30mm to the membrane
in contact with the ground, and 30mm to the internal surface.
b) Slab fabric must be lapped by one full panel of fabric plus 25mm so that the two outermost transverse wires ofone sheet overlap
two outermost transverse wires of the sheet being tapped. Slab fabric is to be supported on bar chairs placed at 80Omm centres.

b) Trench mesh must have all cross wires cut flush with the outer main wires. Trench mesh in slab and edge beams must be
overlapped by the width of the fabric at “T” & “L” intersections. Trench mesh must be spliced, where necessary, by a lap of 500mm.

d) Pre-Fabricated footing cages or reinforcing bars at “T’ & “L” intersections are to have a N12 corner tie bars as per the attached
details.
e) The minimum fap length of reinforcing bar is to be 500mm or 40 bar diameters, whichever greater.

C.5 Masonry Articulation

 

The specifications in this report have been specifically formulated for articulated masonry construction. This usually results lower
construction costs. All masonry walls must have full height articulation at a spacing noted on the first page of this report The articulation
joint must separate the masonry from footing to eaves {evel at this spacing. Masonry must be supported on each side of the joint in an
approved manner to retain its structural integrity.

Where used, internal masonry walls should be articulated in accordance with the masonry manufacturers requirements for the width and
type of unit used. In no instance should the spacing exceed 4.0m and articulation should always be provided at an abutment with an
external wall.

 

 

if articulation of masonry is found to be unacceptabie, the footing system will require re-de: ing.

In addition to joints in masonry, articulation is achieved wherever a 10mm (min) separation in masonry from footings to eaves is achieved.
For example, where timber panels are used above and/or below doors and windows.

  

SCG Consulting Engineers Appendix Page 3 of 7 Appendices.1

Page 10

 

Where it is necessary to construct construction joints to meet the articulation requirements, they can be placed in places of limited visi
For example behind downpipes. Internal masonry walls should be articulated where they abut the perimeter walls.

 

The designer of the building must also ensure that articulation is established:
4. Adjacent to a change in floor level which exceeds 400 mm.

2. if any proposed extension abuts any existing structure, full height articulation must be established where the new masonry joins the
old.
3. Where a masonry wall transgresses from one footing type to another - eg from a perimeter footing to a continuous footing.

If the building has any masonry arches we must be contacted for further advice.

Methods of articulation are well documented in “Technical Note 61” by the Cement & Concrete Association.

D RECOMMENDATIONS

D.1. Recommendations for Builders

Codes of Practice: All construction work associated with this report must be undertaken in accordance with the BCA “part 3.1 — Site
Preparation” and “part 3.2 - Footings & Slabs” and AS2870-2011 “Residential Stabs and Footings’.

 

Underground Services/Piumbing: Where structures are built over filled, soft or loose soils, services will need to be supported so that
potential movement within the soils does not cause them damage or cause incorrect alignment which could cause leakage. Such measures
can include but are not limited to the pro in of expansion joints, sleeved or foam lagged pipe penetrations throughout the structure or
treatment of the soils prior to construction. The attached illustrations detail minimum requirements.

 

 
 

Arrange plumbing fixtures so that the slab and beam penetrations are kept to a minimum and where necessary sleeved to allow for
movement with 40mm thick closed cell polythene or similar material. Where the penetration is within 150mm of the base of a beam or
footing, the depth of this footing element should be deepened by approximately twice the diameter of the penetration. All plumbing and
drainage must comply with the requirements of the National Piumbing and Drainage Code AS3500.

For Class H & E sites, AS2870 - 2011 requires that plumbing
its and foam lagged penetrations.

 

es servicing dwellings in class H & E sites be fitted with sleeved expan:

 

 

Refer to the attached detail sheet “Plumbing Requirements Class M, H and E sites.

  

Site Drainage - Class A Sites: The ground surrounding the dwelling and the building site must be graded and drained so that stormwater
is shed away from the house area in all directions during and after construction. Particular attention should be given to all drainage so
stormwater is not introduced to the foundation soils leading to potential scour. Roof water must be diverted away from the building prior to
and after the roof is installed. Correct drainage is an essential part of our recommendations and design. If the site is not prepared correctly,
excessive foundation movements may occur leading to damage within the supported structure.

 
 

Site Drainage - Class S, M, H & E Sites: The ground surrounding the dwelling and the building site must be graded and drained so that
stormwater is shed away from the house area in all directions, during and after construction. A minimum grade of 1 : 20 (vertical :
horizontal) for 1.5m must be provided. Hard landscaping such as terrace siabs adjacent the dwelling can assist in this. Roof water must be
diverted away from the building site prior to and after the roof is installed. Where building delays occur, temporary downpipes may be
necessary. Constant maintenance of roof drainage is essen If a rainwater tank (or similar) is to be sited in 6 meters of a structural
footing, we should be consulted for further advice. External water taps, air conditioner overflows, tank and hot water cylinder overflows
should be over grated pits connected to the drainage system. The ground surrounding the building must be graded and drained so water is
shed away from the house in all directions.

 
  
 
 

 

Particular care should be taken with drainage, plumbing and electrical trenches so that they do not introduce water to the foundation si
not allow greater soil moisture evaporation and/or destabilise the footings by undermining them. The base of any trenches under the floor or
within 1.5 meters of the building should be sloped away from the house and should be backfilled with compacted clay plug.

 
 

Correct drainage is an essential part of our recommendations and design and is documented in the CSIRO handout BTF-18 attached to the
clients copy of this report. (Additional copies available upon request.) If the site is not prepared correctly, excessive soil moisture may
occur in some areas, which can lead to excessive foundation movements possibly damaging the supported structure.

 

Bracing for Wind Forces: Unless noted, we do not detail slab thickenings or pad footings to conform to wind bracing. Where a bracing
wall is to be bolted to a slab, 40mm bottom concrete cover attained for a radius of 150mm is required around the bolts unless noted by other
consultants.

Inspections: We require 24 hours notice if you require engineers site inspections. Inspections can be booked between 8.30am and 4.30pm
Monday to Friday by telephoning 07 5455 5604.

le for ensuring appropriate silt retention measures are in placed and maintained throughout

 

Silt Retention: The builder is respon
construction.

Site Classification: The site classification is calculated in accordance with the “AS2870-2011 - Residential Slabs and Footings-
Construction” and relates to the estimation of Ys, “The characteristic surface movement” within reactive soil profiles. The limits used for this
classification are as follows:

 

 

 

 

 

 

 

Predicted Surface Movement Classification

Ys = <=20mm Ss Slight

Ys = >20 - 40mm M Moderate
Ys = >40 - 60mm H1 High-1
Ys = 60 - 75mm H2 High-2

Ys => 75mm E Extreme
Problem sites iD Problem

 

 

 

 

scG Consulting Engineers Appendix Page 4o0f7 Appendices.1

Page 11

D.2 Recommendations for Owners

Foundation Maintenance and Owners Responsibilities: The soils surrounding and under the foundations must be protected from scour
or washout from stormwater by ensuring adequate drainage as noted above.

 

Localised concentrations of moisture such as overflows from hot water cylinders or air conditioners can lead to excessive localised

foundation movements and must also be adequately drained away from the foundations as noted above.

  

 

 

In aii types of soil conditions, if an automatic watering system irrigates w! 2.5 meters of a foundations, instability problems and excessive
foundation movements are likely to occur. Also site drainage as discussed above must be maintained.

  

 

ent’s copy of this report. (Ad

 

Ongoing foundation maintenance is documented in the CSIRO handout BTF-18, attached to the
copies available upon request.)

Refer to the attached detail sheet “General Requirements for Site Drainage”

Additional Requirements - Class A & S Sites: Trees and dense shrubs must be kept wel! away from the building foundations. Refer to
the following section “Recommendations — Builders/Owners — Trees’. In all types of soil conditions, if an automatic watering system irrigates
within 2.5 meters of a footing, instability problems may occur. Water should not be allowed to pond on the ground near the building.
hed surface grades around the building should also ensure scour of soils cannot occur. Additional field gullies and drainage might be
required. in all instances the ground should be sioped away from the foundations at a grade of no less than 1 in 20 (vertical to horizontal)
for at least 1.5m.

 

 

 

Additional Requirements - Class M, H & E Sites: Trees and dense shrubs must be kept well away from the building foundations. Refer

to the following section ‘Recommendations — Builders/Owners — Trees”.

The soil near the building should be protected against the increased moisture that occurs in gardens or permeable landscaping built
adjacent the foundations. Automatic irrigation systems must not be used adjacent structural foundations. If required, these forms of
landscaping must be constructed over impermeable membranes that drain the excessive moisture away from the foundations into correctly
installed field gullies and drains.

We strongly recommend the construction of hard landscaped paths or terrace slabs adjacent building foundations for at least a distance of
4.5m to protect the foundations from excessive moisture.

D.3. Recommendations — Builders/Owners - Trees

 

  

Trees and landscaped gardens can have a dramatic influence over the moisture content of the soils they are grown in. This can lead to
increased soil movement through shrinking and swelling. Where these trees or gardens are within close proximity of structural foundations
the soil movements can affect the structural integrity of the foundations.

For Class M, H and E sites the following recommendations for the minimum distance between trees and footings should be followed:-

 

 

 

ite Class Offset to Tree
Class M ; 0.75 xh
Class H ; TOP xh
Class E : 1.5 xh

Where ‘h’ is the mature height of the tree, further refinement of this recommendation can be pursued where tree species can be considered.
Where a row or group of trees exists the above recommendation should be doubled.

in some instances the installation of root barriers can lessen the effect of trees on foundation performance. Please contact SCG Consulting
Engineers for options.

The following table provides some guidance on mature tree heights:-
APPROXIMATE TREE HEIGHTS

 

70 to 20m Height — Acacias, Ash, Athel Tree, Candlebark, Manna Gum, Pepper Tree, Willows, Yate, Yellow Gum

 

 

20 to 30m Height — But-But, Cedars, English Oak, Lemon Gum, Palms, Planes, Sheoaks, Silky Oak, Spotted Gum, Casuarina

 

 

30 to 60m Height ~ Blue Gum, Cypress, English Elm, Figs. Karri, Pines, River Gum, Sugar Gum

 

The removal of trees from the proposed construction can also greatly affect the moisture conditions of the soil. We recommend allowing the
soil time to reach moisture equilibrium prior to construction commencing. Please contact our office for further guidance on this matter.

SCG Consulting Engineers Appendix Page 5 of 7 Appendices.1

 

Page 12

E
E1

SCG Consulting Engineers

DETAIL SHEETS
Plumbing Requirements Class M, H1, H2 & E Sites

 

 

SLAB PENETRATIONS iN TO SATISFY
TERMITE PROTECTION REQUIREMENTS:

‘aS.

 

 

 

FOR SLABS SUPPORTED OH PIERS
PROWDE STAINLESS STEEL

‘SUSPENSION STRAPS FROM SLAB
WESH TO UNDERSLAB DRAINAGE.

 

 

 

 

 

 

 

 

RIS.

FOQING PENETRATION

 

 

   

‘STORM WATER

ORANASE PRE (€Py)

ALLOW PIPE WORK JO NOME”
‘VERTICALLY INDEPENDENT /
OF BUILDING FOOTINGS

 

NES

PLUMBING REQUIREMENTS —

{EPJ)'S 10 UNDERSLAG PIPE
CONMECTIOSN IN GLASS H & E (SYK)

      

 

LEGEND

(EPJ) SELECTED V-UNE "BR AMDAT JONT INSTALLED TO
MANUFACTURERS SPECIRCAIKINS. STORNPLASIICS OR
EQUALLY APPROVED:

‘SELECTED IN-UNE SWAEL JONT INSTALLED TO.
WANUFACTURERS SPEQFICATIONS. STORMPLASRCS OF

(CTP) CONPACTED CLAY PLUMBING TRENCH PLUG To STOP
WAISTURE EXTERNG UNDER THE HOUSE SLAB

(SWL) SEER WAN LN
10. INSPECTION OPENING TO SURFACE

LAGGNG = WHIMUN LAGGNG THICKNESS, 20mm FOR CLASS
‘SITES AND Ximm FOR CLASS H & ESTES

Guidelines for Drainage Installations

 

 

The ving notes and details provided are a guide only for articulation for sanitary
ming, drainage and should be read in conjunction with AS'NZ3500, AS23876 and any

valevart siandard and other requ:rements of the 8.C.
drains instalted in ground th id, unstable, expansive fe.

             

plan and specification should be providec by an appropriately cuatitied person. When a
compliance parmit and assessment is required by the local authority, a scii resort and all
calculations showing oroposed me draimage from poter
movements may be required,

sewer and stermater to be cons’
ants of AS25870 clauses 5.2.5.686.0 4
rovited to accommodate movemen’ pipe work wi
comply AS12860.
ming and drai

  
 

             

 

 

   

Grades fram the face of the footings.
7. Detail and support of traps at the O.R.G to be considered on site to allow for potential
lation and articulation associated with patas and pavements. The

    

 
 

ischarge irom

fixtures such as H.!
authority.

CLASS M Hi H2 & E SITES

 

 

Appendix Page 6 of 7

Appendices.1

Page 13

E2

Site Drainage recommendations

 

ni

DIRECTION OF
GROUND FAL

 

 

 

|
| MELON
!

 

I

 

 

 

 

           

CUT-CEF DRAIN AT HIGH

  

©) GROUND SURFACE FNL
FOOTING & 27 1:20 MIN FOR IS MY

SAB HED

age facilities downslope from
at the upstream enc of the dr

 

SDE GF EMBANKNENT CUT

 

\

a

 

    

CUT-OFF ORAIN ALONG
HICH SDE OF RETANING

RETARING. Laid WAL

      

  

“| ROUND SURFACE FALL
FOOTNG & 1:20 WN FOR Sm NIN

SLAB SHADED

\ 2 REAR OF WALL ORANAGE,
Lok, PROWDE FLUSH OUT
OP” FACUTY

CUT-OFF ORAIN AT BASE
OF RETARING WALL
GARECTED AROUND THE
PERIMETER OF THE
OWELUNG

TYPICAL DRAINAGE ~- RETAINING WALLS

 

SITE DRAINAGE RECOMENDATIONS ALL SITES

 

 

SCG Consulting Engineers

Appendix Page 7 of 7

Appendices.1

Page 14

 

 

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Page 15

Date

 

és
YO Property Boundary

Revision | Description

 

 

 

 

 

 

 

 

 

Property Boundary

 

 

 

 

 

 

 

 

 

 

BH2 .
@ Borehole location.

Gr, Slope
measured as a percentage gradient from
high ground to low ground.

 

DO NOT DIMENSION OFF THIS DIAGRAM.

 

3 LOT 23
a
a dp,
& vy
a
eo" 1
Property Boundary
SITE PLAN
NOOSA DUNES CT
Site Drainage Good.
Vegetation oo

[DESUILD 17%

 

(Property Boundaries are diagramatic only)

SC setral = chil = entchneal &)

ABN 40 098 481 899

 

Unit 1/11 Project Ave, Noosaville
Ph (07) 5455 5604 Fax (07) 5455 5696

 

Title: SITE PLAN

 

Project Lot 23 Noosa Dunes Ct
Noosa Dunes

 

 

Rex. - 30.01.05

Date: Jan 2014 | DrgNo. 23277-S|

 

 

 

 

Page 16

Fer F a ia

eae

a OO .
a as | . - . |

 

Page 17

SCG CONSULTING ENGINEERS LOG SECTIONS Ref No.23277

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Depth TEST SITE No 1 P | Depth TEST SITE No 2 P
100 Silty Sand SM 4 100 Silty Sand SM 1
200 Fine grained, pale grey f 200 Fine grained, pale grey 1
300 Roots, moist, loose. 1 300 Roots, moist, loose. 1
400 1 400 4
500 1 500 1
600 1 600 1
0 a 4 700} 4
800 Silty Sand SM 1 800 Silty Sand SM 4
900 Fine grained, pale grey 1 900 Fine grained, pale grey 1
1000 (White), moist, loose. 1 1000 (White), moist, loose. 4
4100 1 1100 4
1200 1 4200 4
1300 2 | 1300 2
1400 3 1400 Ps
1500 2 | 1500 2
1600 2 | 1600 2
1700 2 | 1700 2
4800 3 | 1800 2
1900 Es 1900 3

2000 3. 2000 3
2100 a) 2100 3
2200 4 2200 3
2300 4 | 2300 4
2400 4 2400 4
2500 5 2500 5
2600 2600
2700 2700
2800 2800
2900 2900
3000 3000
3100 3100

 

 

Depth = mm below ground level.
P = blows per 100mm penetration with an approved 9kg penetrometer.

Notation such as (SP) refers to the soil description to Table A1 AS1726 ‘Guide to the description
identification and classification of soils’.

Solid lines represent sharp interface between different soil types. Dotted lines represent
gradation form one soil type to another.

Abbreviations used

UTP - unable to penetrate, Bec. — becoming, N.S.L. ~ Natural Surface Level
Med. -- medium, MW - Moderately weathered

EW - extremely weathered, Piast. - Piasticity

 

No recovery means unable to extract samples from the base of the bore hole because the soil
will not bind in the auger head.

The colour of the soil is often abbreviated, for example Gy = grey Or = orange.
(Ls=?.?%) Indicates sample location and Linear Shrinkage result.

The footings must be dug into or supported on piers dug into the shaded material.

 

 

 

Page 18

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Page 19

Foundation Maintenance
and Footing Performance- =

reptaces

A Homeowner's Guide Saane

Buildings can and often do move. This movement can be up, down, lateral or rotational. The fundamental cause
ngs can usually be related to one or more probiems in the foundation soil. It is important for
the homeowner to identify the soil type in order to ascertain the measures that should be put in place in order to
ensure that problems in the foundation soil can be prevented, thus protecting against building movement.

This Building Technology File is designed to identify causes of soitrelated building movement, and to suggest
methods of prevention of resultant cracking in buildings.

 

 

 

‘So Types Erosion

All soils are prone to erosion, but sandy soil is particularly susceptible
The types of soils usually present under the topsoil in land zoned for to being washed away. Even clay with a sand component of say 10%

 

residential buildings can be split into two approximate groups ~ or more can suffer from erosion.

granular and clay. Quite often, foundation soil 1s a mixture of both

types. The genera problems associated with soils having granular Saturation

content are usually caused by erosion. Clay sails are subject to This is particularly a problem in clay soils. Saturation creates a bog-

like suspension oe soil that causes it to lose virtually ail of its
: bearing capacity. To a lesser de; , San

Classifications for a given area can generally be obtained by bee es a ae A a d aa eee ora Py. eee
application to the local authority, but these are sometimes unreliable particularly imported san ‘d fill for bedding and blinding layers.
and if there is doubt, a geotechnical report should be commissioned. However, this usually occurs as immediate settlement a ae Id
As most buildings suffering movement problems are founded on clay nor aly) be the ones of the builder. i
soils, there is an emphasis on classification of soils according te the :

saturation and swell/shrink problems.

 

amount of swell and shrinkage they experience with variations of Seasonal swelling and shrinkage of soil
water content, The table below is Table 2.1 from AS 2870, the All clays react to the presence of water by slowly absorbing it, making
Residential Slab and Footing Code. the soil increase in volume {see table below). The degree of increase
J varies considerably between different clays, as does the degree of
Causes of Movement decrease during the subsequent drying out caused by fair weather,
Sateen ae ae eae periods. Because of the low absorption and expulsion rate, this
Th Raat RInR phenomenon will not usually be noticeable untess there are
ere are two types of settlement that occur as a result 0! prolonged rainy or dry periods, usually of weeks or months,
construction: depending on the land and soil characteristics.
© Immediate settlement occurs when a building is first placed on its
foundation soil, as a result of compaction of the soil under the The swelling of soil creates an upward focce on the footings of the
weight of the structure. The cohesive quality of clay soil mitigates building, and shrinkage creates subsidence that takes away the
against this, but granular (particularly sandy) soil is susceptible. support needed by the footing to retain equilibrium.

» Consolidation settlement is a feature of clay soil and may take

place because of the expulsion of moisture from the soil or because Shear failure

of the soil’s lack of resistance to local compressive oF shear stresses. This phenomenon occurs when the foundation soll does not have
This will usually take place during the first few months after sufficient strength to support the weight of the footing. ‘There are
construction, but has been known to take many years in two major post-construction causes:

exceptional cases. * Significant load increase.

These problems are the province of the builder and should be taken + Reduction of lateral support of the soil under the footing due to

into consideration as part of the preparation of the site for construc- erosion or excavation.
tion. Building Technology File 19 (BTF 19) deals with these + Inclay soil, shear failure can be caused by saturation of the soil
problems. adjacent to or under the footing.

 

 

Tae "GENERAL DEFINITIONS OF SITE CLASSES

 

Bee ee ea eet G2 Foundation -

 

 

 

A Most sand and rock sites ii little Or no ground movement from moisture changes 5
Soe x Slightly ceactive clay sites with only slight ground movement from moisture changes
M:: ‘Moderately reactive clay of silt sites, Which can experience moderate ground movement from moistuce changes *

He ; Highly reactive clay sites, which can experience high ground imayement fromm mdisttire changes

“| Bxtremely reactive sites, which can experience extreme ground irioverent fram moisture charges

 

 

AtoP. |. © Filled sites

x Sites which include soft soils, such as soft clay or silt or loose sands; landslip; mine subsidence; collapsing soils} soils subject
td erosion, reactive Sites subject to abnormal moisture conditions or ‘sites which canriot be classified otherwise "

 

 

 

Page 20

Tree root growth
Trees and shrubs that are allowed to grow in the vicinity of footings
tion soil movement in two ways:

can cause f

 

* Roots that grow under footings may increase in cross-sectional
size, exerting upward pressure on footings.

* Roots in the ity of footings will absorb much of the moisture
in the foundation soil, causing shrinkage or subsidence.

 

/Unevenness of Movement

The types of ground movement described above usually occur
unevenly throughout the building's foundation soil. Settlement due
to construction tends to be uneven because of:

+ Differing compaction of foundation soil prior to construction.
¢ Differing moisture content of foundation soil prior to construction.

Movement due to non-construction causes is usually more uneven
still. Erosion can undermine a footing that traverses the flow or can
create the conditions for shear failure by eroding soil adjacent to a
footing that runs in the same direction as the flow.

Saturation of clay foundation soil may occur where subfloor walls
create adam that makes water pond. It can also occur wherever there
is a source of water near footings in clay soil. This ieads to a severe
reduction in the strength of the soil which may create local shear
failure.

Seasonal swelling and shrinkage of clay soil affects the perimeter of
the building first, then gradually spreads to the interior. The swelling
process will usually begin at the uphill extreme of the building, or on
the weather side where the land is flat. Swelling gradually reaches the
interior soil as absorption continues. Shrinkage usually begins where
the sun's heat is greatest.

: Effects of Uneven Soil Movement on Structures

Erosion and saturation

Erosion removes the support from under footings. tending to create
subsidence of the part of the structure under which it occurs.
Brickwork walls will resist the stress created by this removal of
support by bridging the gap or cantilevering until the bricks or the
mortar bedding fail. Older masonry has little resistance. Evidence of
failure varies according to circumstances and symptoms may include:

* Step cracking in the mortar beds in the body of the wall or
above/below openings such as doors or windows.

* Verticai cracking in the bricks (usually but not necessarily in line
with the vertical beds or perpends).

Isolated piers affected by erosion or saturation of foundations will
eventually lose contact with the bearers they support and may tilt or
fall over. The floors that have fost this support will become bouncy,
sometimes rattling ornaments etc.

 

Swelling foundation soil due to rainy periods first lifts the most
exposed extremities of the footing system, then the remainder of the
perimeter footings while gradually permeating inside the building
footprint to lift internal footings. This swelling first tends to create a
dish effect, because the external footings are pushed higher than the
internal ones.

The first noticeable symptom may be that the floor appeats slightly
dished. This is often accompanied by some doors binding on the
floor or the door head, together with some cracking of cornice
mitres, In buildings with timber flooring supported by bearers and
ts, the floor can be bouncy. Externally there may be visible
dishing of the or ridge lines.

 
   

As the moisture absorption process completes its journey to the
innermost areas of the building. the internal footings will rise. If the
spread of moisture is roughly even, it may be that the symptoms will
temporarily disappear, but it is more likely that swelling will be
uneven, creating a difference rather than a disappearance in
symptoms. In buildings with timber flooring supported by bearers
and Joists. the isolated piers will rise more easily than the strip
footings or piers under walls, creating noticeable doming of flooring.

Set ee eee ee

 

As the weather pattern changes and the soil begins to dry out, the
external footings will be first affected, beginning with the locations
where the sun’s effect is strongest. This has the effect of lowering the
external footings. The doming is accentuated and cracking reduces
or disappears where it occurred because of dishing, but other cracks
open up. The roof lines may become convex.

Doming and dishing are also affected by weather in other ways. Tn
areas where warm, wet summers and cooler dry winters prevail,
water migration tends to be toward the interior and doming will be
accentuated, whereas where summers are dry and winters are cold
and wet, migration tends to be toward the exterior and the
underlying propensity is toward dishing.

Movement caused by tree roots

In general, growing roots will exert an upward pressure on footings,
whereas soil subject to drying because of tree or shrub roots will tend
to remove support from under footings by inducing shrinkage.

Complications caused by the structure itself

Most forces that the soil causes to be exerted an structures are
vertical ~ i.e. either up or down. However, because these forces are
seldom spread evenly around the footings, and because the building
resists uneven movement because of its rigidity, forces are exerted
from one part of the building to another. The net result of all these
forces is usually rotational. This resultant force often complicates the
diagnosis because the visible symptoms do not simply reflect the
original cause. A common symptom is binding of doors on the
vertical member of the frame.

 

Effects on full masonry structures

Brickwork will resist cracking where it can. It will attempt to span
areas that lose support because of subsided foundations or raised
points. It is therefore usual to see cracking at weak points, such as
openings for windows or doors.

In the event of construction settlement, cracking will usually remain
unchanged after the process of settlement has ceased.

With local shear or erosion, cracking wilt usually continue to develop
until the original cause has been remedied, or until the subsidence
has completely neutralised the affected portion of footing and the
structure has stabilised on other footings that remain effective.

In the case of swell/shrink effects. the brickwork will in some cases
return to its original position after completion of a cycle, however it
is more likely thal the rotational effect will not be exactly reversed,
and it is also usual that brickwork will settle in its new position and
will resist the forces trying to return it to its original position. This
means that in a case where swelling takes place after construction
and cracking occurs. the cracking is likely to at least partly remain
after the shrink segment of the cycle is complete. Thus, each time
the cycle is repeated, the iikelihood is that the cracking will become
wider until the sections of brickwork become virtually independent.

With repeated cycles, ance the cracking is established. if there is no
other complication. it is normal for the incidence of cracking to
stabilise, as the building has the articulation it needs to cope with
the problem. This is by no means always the case, however, and
monitoring of cracks in walls and floors should always be treated
seriously.

 

Upheaval caused by growth of tree roots under footings is not a
simple vertical shear stress. There is a tendency for the raot to aiso
exert lateral forces that attempt to separate sections of brickwork
after initial cracking has occurred.

Page 21

The normal structural arrangement Is that the inner leaf of brick-
work in the externai waiis and at ieasi some ‘of the internal walls
{depending on the roof type) comprise the load-bearing structure on
which any upper floors, cellings and the roof are supported. In these
cases, it is internally visible cracking that should be the main focus
of attention, however there are a few examples of dwellings whose
external leaf of masonry plays some supporting role, so this should
be checked if there is any doubt. In any case, externally visible
cracking is important as a guide to stresses on the structure generally,
and it should also be remembered that the external walls must be

capable of supporting themselves.

Effects on framed structures

Timber or steel framed buildings are less likely to exhibit cracking
due to swell/shrink than masonry buildings because of thelr
flexibility. Also, the doming/dishing effects tend to be lower because
of the lighter weight of walls. The main risks to framed buildings are
encountered because of the Isolated pier footings used under walls.
Where erosion or saturation cause a footing to fail away, this can
double the span which a wall must bridge. This additional stress can
create cracking in wall linings, pacticularly where there is a weak
point in the structure caused by a door or window opening. It is,
however, unlikely that framed structures will be so stressed as to suffer
serious damage without first exhibiting some or all of the above
symptoms for a considerable period, The same warning period should
apply in the case of upheaval. It should be noted, however, that where
framed buildings are supported by strip footings there is only one leaf
of brickwork and therefore the externally visible walls are the
supporting structure for the building. Tn this case, the subfloor
masonry walls can be expected to behave as full brickwork walls.

Effects on brick veneer structures ;

Because the load-bearing structure of a brick veneer building is the
frame that makes up the interior leaf of the external walls plus
perhaps the internal walls, depending on the type of roof, the
building can be expected to behave as a framed structure, except that
the external masonry will behave ina similar way to the external leaf
of a full masonry structure.

  

‘Where a water service pipe, 2 sewer or stormwater drainage pipe is in
the vicinity of a building, a water Jeak can cause erosion, swelling or
saturation of susceptible soil. Even a minuscule leak can be enough
to saturate a clay foundation, A leaking tap near 2 building can have
the same effect, In addition, trenches containing pipes can become
watercourses even though backfilled, particularly where broken
rubble Is used as fill, Water that runs along these trenches can be
responsible far secious erosion, interstrata seepage into subfloor areas
and saturation.

Pipe leakage and trench water flows also encourage tree and shrub
roots to the source of water, complicating and exacerbating the
soblem. 7
oor roof plumbing can result in large volumes of rainwater being
concentrated in a small area of soil:

» Incorrect falls in roof guttering may result in overflows, as may
gutters blocked with leaves eic.

* Corroded guttering or downpipes can spill water to ground.
* Downpipes not positively connected to a proper stormwater

Downpipes not p

 

collection system will direct a concentration of water to soli that is
directly adjacent to footings, sometimes causing large-scale
problems such as erosion, saturation and migration of water under
the building.

  

of Cracking

In general, most cracking found in masonsy walls Is a cosmetic
nuisance only and can be kept in repair or even ignored, The table
below is a reproduction of Table C1 of AS 2870. ;

AS 2870 also publishes figures relating to cracking in concrete floors,
however because wall cracking will usually reach the critical point
significantly earlier than cracking in slabs, this table is not
reproduced here.

'Prevention/Cure

 

Piumbing

Where building movernent is caused by water service, roof plumbing,
sewer or stormwater failure, the remedy is to repair the problem.

It fs prudent, however, to consider also rerouting pipes away from
the building where possible, and relocating taps to positions where
any leakage will not direct water to the building vicinity. Even where
gully traps are present, there Is sometimes sufficient spill to create
erosion of saturation, particularly in modern installations using

” sinaller diameter PVC fixtures. Indeed, some gully traps are not
~ situated directly under the taps that are installed to charge them,

with the result that water from the tap may enter the backfilled
trench that houses the sewer piping. If the trench has been poorly
backfilled, the water will either pond or flow along the bottom of
the trench. As these trenches usually run alongside the footings and
can be at asimilar depth, it 's not hard to see how any water that is
thus directed into a trench can easily affect the foundation's ability to
support Footings or even gain entry to the subfloor area.

Ground drainage

Tn all soils there is the capacity for water to travel on the surface and
below it. Surface water flows can be established by inspection during
and after heavy or prolonged rain. Tf necessary, a grated drain system
connected to the stormwater collection system js usually an easy
solution.

Tt is, however, sometimes necessary when attempting to prevent
water migration that testing be carried out to establish watertable
height and subsoil water flows. This subject Is referred to in BTF 19
and may properly be regarded as an area for an expert consultant.

Protection of the building perimeter ne
It is essential to remember that the soil that affects footings extends
well beyond the actual building Line. Watering of garden plants,
shrubs and trees causes some of the most serious water problems,

For this reason, particularly where problems exist or are Likely to
‘occur, it is recommended that an apron of paving be installed
around as much of the building perimeter as necessary. This paving

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Page 22

         

_. Orained
athway:

 

Carport

 

should extend outwards a minimum of 900 mm {more in highly
reactive soil) and should have a minimum fall away from the
building of 1:60. The finished paving should be no less than 100
mm below brick vent bases.

Tt is prudent to relocate drainage pipes away from this paving. if
possible, to avoid complications from future leakage. If this is not
practical. earthenware pipes should be replaced by PVC and
backfilling should be of the same soil type as the surrounding soil
and compacted to the same density.

Except in areas where freezing of water is an issue, it is wise to
remove taps in the building area and relocate them well away from
the building — preferably not uphill from it (see BTF 19).

Tt may be desirable to install a grated drain at the outside edge of the
paving on the uphill side of the building. if surbsoii drainage is
needed this can be installed under the surface drain.

Condensation

In buildings with a subfloor void such as where bearers and joists
support flooring, insufficient ventilation creates ideal conditions for
condensation, particulariy where uf is little clearance beiween
floor and the ground, Condensation adds to the moisture alceady
present in the subfloor and significantly slows the process of drying
out. Installation of an adequate subfloor ventilation system, either
natural or mechanical, is desirable.

 
 

  

Warning: Although this Building Technology Fite deals with
cracking in buildings, it should be said that subfloor moisture can
result in the development of other problems, notab!

 

* Water that is transmitted into masonry, metal or timber building
elements causes damage and/or decay to those elements.

> Hi
environment for various pests. including termites and spiders.

subfloor humidity and moisture content create an ideal

 
  

« Where high moisture levels are transmitted to the flooring and
walls, an increase in the dust mite count can ensue within the
living areas. Dust mites, as well as dampness in general, can be a
health hazard to inhabitants, particularly those who are
abnormally susceptible to respiratory ailments.

 

The garden

The ideal vegetation layout is to have lawn or plants that require
only light watering immediately adjacent to the drainage or paving
edge. then raore demanding plants, shrubs and trees spread out in
that order.

 

Overwatering due to misuse of automatic watering systems is a
common cause of saturation and water migration under footings. If
it is necessary to use these systerns, it is important to remove garden
beds to a completely safe distance from buildings.

Existing trees

Where a tree is causing a problem of soil drying or there is the
existence or threat of upheaval of footings, if the offending roots are
subsidiary and their removal will not significantly damage the tree,
they should be severed and a concrete or metal barrier placed
vertically in the soil to prevent future root growth in the direction of
the building. If it is not possible to remove the relevant roots
without damage to the tree, an application to remove the tree should
be made to the local authority. A prudent plan is to transplant likely
offenders before they become a problem.

Information on trees, plants and shrubs

State departments overseeing agriculture can give information
regarding root patterns, volume of water needed and safe distance
fram buildings of most species. Botanic gardens are also sources of
information. For information on plant roots and drains, see Building
Technology File 17.

Excavation

Excavation around footings must be properly engineered. Soil
supporting footings can only be safely excavated at an angle that
allows the soil under the footing to remain stable. This angle is
called the angle of repose (or friction) and varies significantly
between soil types and conditions. Removal of soil within the angle
of repose will cause subsidence.

 

Where erosion has occurred that has washed away soil adjacent to
footings, soil of the same classification should be introduced and
compacted to the same density. Where footings have been
undermined, augmentation or other specialist work may be required,
Remediation of footings and foundations is generally the realm of a
specialist consultant.

Where isolated footings rise and fail because of swell/shrink effect.
the homeowner may be tempted to alleviate floor bounce by fil
the gap that has appeared between the bearer and the pier with
blocking. The danger her: hen the next swell segment of
cycle occurs, the extra blocking will push the floor up into an
accentuated dome and may also cause local shear failure in the so’
Tf it is necessary to use blocking, it should be by a pair of fine
wedges and monitoring should be carried out fortnightly.

 

  
  

 
  

 

This BTF was prepared by John Lewer FAIB, MIAMA, Partner,
Construction Diagnosis.

 

 

The information in this and other issu

 
 

 
 

in the series was gerived ccm various sources and was believed ta be correct when pul

 

‘The information is adv si ttis pew ed in good faith and not ‘claimed 0 be an exraustve| treatm

  

 

of the relevant Su

 

 

Further Professional advice needs to be obrained before taking any a action based ¢ on 1 the einforration proved.

  

 

 
 

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