W6107fd f15.pdf - form 15 footing & slab design · OPW16/0220

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5. Building certifier reference number              Building certifier reference number



6. Competent person details                         Name (in full)
A competent person for building work, means a
person who is assessed by the building certifier
for the work as competent to practise in an
                                                     Ray Williams.
aspect of the building and specification design,    Company name (if applicable)                          Contact person
of the building work because of the individual’s
skill, experience and qualifications in the          Sunrise Design Qld Pty Ltd.                           Ray
aspect. The competent person must also be
registered or licensed under a law applying in      Phone no. business hours              Mobile no.                    Fax no.
the State to practice the aspect.                    5442 5930                                                           5442 5934
If no relevant law requires the individual to be    Email address
licensed or registered to be able to give the
help, the certifier must assess the individual as
having appropriate experience, qualifications or
skills to be able to give the help.                 Postal address
If the chief executive issues any guidelines for     PO Box 621, Cooroy.
assessing a competent person, the building
certifier must use the guidelines when                                                                                   Postcode Q 4563
assessing the person.
                                                    Licence or registration number (if applicable)
                                                     RPEQ 2166
7. Signature of competent person                    Signature                                                    Date
This certificate must be signed by the individual                                                                  September 27, 2016
assessed by the building certifier as competent.




                   The Building Act 1975 is administered by the
                   Department of Infrastructure and Planning
                                                                                                       Department of Infrastructure and Planning

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Report No:    W6107fd.
Client Name: K Grandemange
Report Date: September 27, 2016
Site Address: No 61 Morinda Circuit, Noosaville.

                                  Footing Design Report.

a)     Site Classification.
b)     Constructing Building Platform.
c)     Stiffened Raft & Pad Footings.
d)     Building measurements & siting and existing services.
e)     Footing & slab inspections.
f)     Definitions.
g)     Construction & maintenance notes 1 & 2.
h)     Footing & Slab layout – W6107fd drawings

We advise all owners and occupiers of the structures designed in this report to read,
understand and follow the construction & maintenance notes - especially where relating
to watering & planting of trees, shrubs & garden beds. It is also important that the
proposed site drainage be maintained and is not impaired by future landscaping.

Site Classification & Drawings.

This footing design is based on the site investigation report S7920 not attached – Class
“H1” – Ys = 45-50 mm - as per AS2870 - 2011, Residential slabs and footing code.

Changing the soil profile by adding fill or cutting will change the site classification.

Constructing Building Platform.

Follow construction notes as per attached drawings W6107fd. Where level platforms are
required, the platform must be 3 metres in width larger than the proposed structure.

Stiffened Raft & Pad Footings.

All footings are to be constructed as per the footing & slab design indicated in drawings
W6107fd and founded a minimum of 300mm into the natural stiff silty clay \referred to
as the target foundation material – see site investigation logs.

Stiffened raft footings must be deepened to past fill or other natural material, to be
founded into the target foundation material.




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Building measurements & siting and existing services.

The builder must ensure the building is located in the correct location and building
dimensions are used from architectural plans and not measured from the footing & slab
plan.
The sewer line indicated is the only service line identified on site which could influence
the footing performance. We were not informed of any other existing services line
excavations. Where other service line excavations do exist and are not identified or
specifically addressed by the footing design; then the footing & slab elements above the
critical line must be piered to below the stable line indicated in the attached drawing
“supporting footings near temporary excavations” .

Footing & slab inspections.

The person inspecting the footing and slab must check that the soil types are
representative of the ground profiles indicated in the soil logs and the site preparation is
as recommended. Where the ground profiles or the site preparation differ significantly
from the information supplied the designer must be contacted for further advice.




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Definitions.

Site classification – a broad measure of the potential ground movement of a site when
this site is subjected to loading by a structure (generally residential) and for a given and
controlled range of soil moisture changes – where the suction depth Hs is equal or
greater than 3 metres the classification is modified by adding a – D after the
classification letter ie M-D – class M with deep soil moisture suction changes.

AS2870 - 2011 has defined 7 site classes as follows:

Class                         Foundation movement from               Ys - site movement
                              Moisture changes

A - stable                    sand & rock sites.                     NA

S - slightly reactive         slightly reactive clays                0 to 20 mm

M – moderately reactive       moderately reactive clays              21 to 40mm

H1 – highly reactive          highly reactive clays                  41 to 60mm

H2 – highly reactive          very highly reactive clays             61 to 75mm

E – extremely reactive        extremely reactive clays               75+mm

P – problem                   varies                                 0 to 75+mm

Note: Problem (P) sites are normally classified because of limited bearing strengths at
normal footing depths - say 200mm below the ground surface where it is expected the
footings are to be supported by piers founded into strong material or where applicable
smaller differential movements can be catered for in the design by supporting the
structure with a heavy stiffened raft. Where a stiffened raft cannot cope with large
differential movements (or becomes less economic) then piles or piers are designed to
support the structure

Controlled fill – fill that has been placed & compacted in layers by compaction
equipment to a density defined by AS 3798 (Guidelines on earthworks for commercial
& residential developments) and able to achieve 100 kPa safe bearing capacity.

Rolled fill – fill compacted by rolling with an excavator. Sand material – compacted in
200mm layers up to 600mm thick. Clay based material – compacted in 150mm layers up
to 300mm thick. Where stated in this report “as rolled fill” the compaction is the same
but fill thickness may be increased and the footing and slab is supported on piers where
any fill exceeds 250mm in thickness.

Uncontrolled fill – fill that is neither rolled fill or controlled fill and which may cause
excessive settlement under footing & slab loads.




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Construction & Maintenance Note 1 - Controlling moisture around the structure (H).

The diagram below is mostly self-explanatory and the aim is to prevent excessive
moisture coming into contact with the foundation soils.
Where watering occurs the moisture must be applied as evenly as possible and the
foundation soils should not be saturated but moistened.

After construction it is not recommended to fill more than 50mm in depth within 3
meters of the structure and where this occurs the ground surface must be graded to
maintain a 1:20 fall away from the structure.

Where landscaping is undertaken the end result must not reduce the drainage around the
structure or creates a situation where moisture is concentrated in a small area so as to
cause uneven wetting of the foundation soils.

                           Gutter & down pipes are to be kept clean of
                           leaves & leaks are to be fixed promptly.
                                                                         Taps are to be turned off, do not
                                                                         leak & have grates to discharge
                                                                         overflow to storm water system.
Plumbing leaks are to be
fixed promptly.                    Structure designed.
                                                                         Sprinkler systems to be prevented
                                                                         from significantly wetting up the
                                                                         foundation soils - best if watering
                                                                         is light & even around structure.

Ground level


                           Foundation soils.
                                                                                           2 metres.


      2.5 metres                                                          2.5 metres


The ground surface must be graded to slope away
from the perimeter of the structure & the owner/occupier
must not change the grade of the ground surface.




Maintenance of gutters, taps & plumbing & sprinkling control – H Reactivity Soils.




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Construction & Maintenance Note 2 - Planting of trees, shrubs and garden beds (H).

It is known that shrubs and trees have root systems that can dry clay-based foundation
soils to a greater degree and to greater depths than the drying effect caused by the
weather and climate (weather and climate are normally referred to as seasonal variation).

This excessive drying of the clay-based foundation soils can result in shrinkage of the
foundation soils and subsequent footing movements can be up to 2 to 3 times the ground
movement caused by seasonal variations.
Excess ground movement is likely to cause cracking in masonry walls.

It is noted that timber framed walls clad with say weatherboards or fibrous sheeting is
more tolerant to the effects of ground movement than masonry walls.

Footings are normally designed to cope with ground movements generated only by
seasonal variations in ground moisture content. A footing designer must know in
advance the extent of vegetation to be allowed for in the footing design – this is not
often considered in the footing design unless the area has established trees which are
going to be left after the new structure is built. The cost of the footing system can be
increased significantly if the effect of trees is allowed for in the footing design.

Existing trees are often removed well before the construction of a new dwelling or
structure and the planting of new trees and shrubs and/or the position of existing
vegetation must comply with the diagram below to reduce the risk of structural damage
(see figure 4.1 below).

                                                                                  Mature
                                                                                  height
                                                                                  of trees
                                           2.5 meters minimum to
                                            small flower gardens.
                      Structure designed
Ground level
2m                Foundation soil

               2.5m                        2.5m

                                            Minimum 1 x mature
                                            height of tree and shrub.

                                            Minimum 1.5 x mature height
                                            or group trees or shrubs

Position of gardens, shrubs & trees to slabs & footings – H Reactivity Soils.




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