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Frequently Asked Questions

Cracks in Brickwork
Question – I live in a brick home that was built on a clayey site in the early 80′s. Recently, I started to recognise some cracks developing in the brick work. Is this dangerous? Will these cracks get bigger & How to fix the problem?
Answer Some minor cracking in masonry walls is inevitable. Cracks up to 1mm would be expected in most houses. Large cracks up to 5mm may occur in some houses with properly designed and constructed footings. Cracks larger than 5mm are regarded as significant damage.One of the main reason for the cracks in the brick work is water reacting with the existing clayey soil. Clay has the ability to absorb moisture and swell very quickly when soaked in water. As the soil swells, the brickwork supported on this soil will camber, and experience an upward movement. In dry seasons, as clay starts loosing its moisture content it starts shrinking to its original volume causing cracks along the weakest parts of the building mainly around windows and doors openings.It is always important to minimise changes in the clay by 1. Properly draining the site; 2.Keep gardens and trees away from the building line of the house; 3. Provide adequate & moderate garden watering; 4. Repare any Plumbing leaks.
Inadequate Footings Depth
Problem – Most Buildings built on clayey sites prior to 1990 got footings way below the recommendations in AS 2870 due to deficiencies in the previous Codes & Standards.
SolutionUnderpinning the foundation, as per attached file provides a solution for under-designed footings.
Smaller retaining wall footings
Problem: A footing for a free standing retaining wall 2.0m high can be as wide as 1.4m, what can we do to reduce the footing width?

SolutionIf the top of the retaining wall is braced or pinned, the footing width of the retaining wall can be as small as 450mm wide. Extra reinforcement to be provided in the wall to cater for the additional stresses exerted.

Temporary Shoring
Problem: What do we do if we are excavating next to an existing building with a retaining wall to be built at a later stage?
Solution: Provide SL82 Mesh 75mm off the ground. Mesh to be held in position using N12 galvanised hooked bars driven 0.5m into the embankment at 1.2m center to center each way, then shotcrete the soil with a layer of 150mm thick concrete.