Here at Jim’s Building Inspections one of the most common causes of “first three year cracking” in a new construction that we find, is due to the neglect of the homeowner to follow the recommendations set out in the SITE & SOIL INVESTIGATION & FOOTING DESIGN & CONSTRUCTION REPORT. These recommendations can be used as a guide in regard to older properties also.
In laymen’s terms this is a report compiled by a Structural Engineer detailing the specific sites soil structure and recommendations for minimising the impact on the dwelling from soil wetting or drying among many other things.
Below is a standard extract from one of the said reports.
Because differential moisture variation (ie wetting or drying) which is the main cause of movement in clay soils, the achievement of effective drainage is of the greatest importance as it reduces the chance of footings having to cope with extremes of soil movement. The following list covers the common causes of moisture variation:-
1) Leaking sewer or water pipes.
2) Downpipes discharging too close to the house.
3) Sloping sites and inadequate drainage causing water to pond or collect close to the building.
4) Seepage on sloping sites caused by water travelling on the topsoil-clay interface. Cut off drains are required in this situation.
5) Garden or lawn watering immediately adjacent to the footings. As a general rule this is not acceptable and must not be done except with the explicit approval of the Engineer.
6) Septic tanks with inadequate soakage trenches.
7) Flooding during house construction.
1) The non-provision of paving particularly on the north and west sides of the house coupled with the non-establishment of a garden.
2) A change from an established garden situation to a native garden coupled with a substantially reduced level of watering.
3) The most common cause of drying out by far is that caused by trees being planted too close to the house. Single trees should be planted a distance from the house equal to the expected mature height of the tree. Where there is more than one tree in a row or group this distance would be increased to 1.5 times the expected mature height.
Because of the above factors the following work must be done :
(a) Establish lawns and gardens around the building as soon as possible and certainly within six (6) months of occupation of the building.
(b) Ensure all roof storm water is discharged to the street where possible or alternatively discharged on the low side of the site not less than 6m from the building, but not so as to concentrate a flow of water onto neighbouring property. (Refer drainage plan in the report), or as shown on the architectural drawings.
By having a staged New Construction Building Inspection and following the recommendations in your site specific report, and or CSIRO recommendations you will significantly reduce the risk of failure to your dwellings “back bone” the footings.
It is also worth noting that cracks, <1mm, category 1 cracks are not required to be repaired by a builders warranty and if you fail to adhere to these guidelines most builders will not take any blame whatsoever no matter the size or nature of the cracking.
Please find below a link to a CSIRO website explaining the issue in more depth:
So if you have a new property and want to ensure you reduce the risk of failure to your footings get in touch with us for a new construction inspection in Perth, Melbourne, Brisbane or Sydney.