Residential
Building Settlement Problems
STG provides turnkey solutions for buildings under structural stress. From engineering investigation and reporting through to the remedial works we offer rapid professional engineer certified solutions.
Download the 2011 STG Homeowners Guide on Foundation Settlement.
Over time all foundations move. Where movement exceeds the intended design allowance the excess can causes the foundation to become overstressed resulting in masonry cracks and gaps at door and window openings. Excessive foundation movement can compromise a buildings structural integrity.
Excluding render or plasterwork hairline shrinkage cracks masonry cracks and gaps that appear are usually the result of:
1. Poor Initial Construction Methods
2. Changing Environmental Conditions
3. Building Alterations and Additions
4. Age of Building
Assuming the foundation system was designed by a qualified engineer, construction should be in accordance with the specified design outcomes. In other words there is a process that needs to be adhered to and any deviation may affect foundations performance.
Builders have to address the economical challenges of completing the construction on or as close to budget as possible. Unless a builder’s contract allows for latent ground conditions he can be subjected to increased costs and he may be tempted to take shortcuts.
An experienced builder understands shortcuts in foundation construction can cost him money during his maintenance guarantee period if a building starts to move. Nowadays it is rare for an engineer to inspect domestic construction foundations prior to concrete pours so builders must supervise and trust his foundation contractor more than ever.
Natural and manmade environmental changes may negatively influence foundation performance. The problem is lessened where a sub-foundation system such as screwpiles is part of the original design. Any one of the following environmental changes can impact on a foundation system:
· Significant changes in soil moisture
· Changes to watertable levels
· Removal of surrounding trees
· Adjacent excavations (old and new)
· Incorrect excavation compaction
· Proximity dewatering & water bore use
Problems associated with the post construction of basements, cellars and pools can appear many years later as soil slowly moves to consolidate uncompacted excavation fills.
Since the early 1900 foundation technology has come a long way. In Western Australia older housing (pre-1950’s) located on sand sites was constructed on simple foundations of “brick on flat”, which consisted of a double row of bricks laid flat on the sand with wall built atop. Another method was to lay large limestone blocks with double cavity brick walls constructed atop. Both methods created a very rigid structure and assumed virtually no soil movement would occur.
Whilst many houses in excess of 100 years are still standing it is expected that during the course of its life it will have experienced some form of foundation movement possibly requiring remedial work. Our Australian Building Codes typically designs housing for 50-75 year design life.
From the 1970’s concrete strip footings and beams under concrete slabs were introduced. This system is still used today in many configurations in accordance with the site ground conditions. Various configurations are used on both sand and clay sites.
One of the biggest problems associated with older buildings is that of environmental change such as changes to ground moisture or where tree removal or close proximity excavation has occurred. One of the first indications of a problem is cracks in walls and gapping along door or window openings. The recent rubbing or jamming of doors and windows can be a good indication that the buildings foundations are moving excessively.
