Slope Stability Report (rec. 16.04.25) · MCU25/0042

Trees: Trees can have a considerable influence over the over the performance of a structures foundation, in particular those founded on
reactive soils (Class S, M, H & E). The trees demand 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. We are unable to assess for the potential effects of trees planted after our testing, reference should be made to
“Recommendations for Builders/Owners-Trees” in Appendix D that 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 slope 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”.



E         RECOMMENDATIONS
E.1     Recommendations for Builders and Foundation Designers
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 Slabs and Footings”.
Underground Services/Plumbing: 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 provision 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 Plumbing and Drainage Code AS3500.
For Class H & E sites, AS2870 - 2011 requires that plumbing pipes servicing dwellings in class H & E sites be fitted with sleeved expansion
joints, rotational swivel joints and foam lagged penetrations.
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. 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 slabs 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 essential. If a rainwater tank (or similar) is to be sited within 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 moisture into the soils supporting
the foundations 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 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.
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.
Silt Retention: The builder is responsible for ensuring appropriate silt retention measures are in placed and maintained throughout
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                                  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

 Australian Soil Investigations                                Appendix Page 3 of 6                                               Appendices.1