Cracks in Brickwork
The nature and size of cracks in the brick work of a house can give a good indication to the overall structural performance.
Fine cracks less 1mm in width do not usually pose a structural concern; they are often the common result of mortar shrinkage.
Cracks between 1 - 3 mm usually are a result of mortar shrinkage and minor foundation settlement. Depending on the age of the house the degree for concern can vary but while they are less than 3mm it does not usually constitute a concern of structural failure.
Cracks ranging from 5 - 10mm are indeed a greater cosmetic concern and are indications leading to a moderate structural failure. Depending on the extent and locations of the cracks, there may be a need for structural underpinning. Underpinning is an expensive and disruptive time consuming repair of the footings that support the brick work.
Cracks greater than 15mm signal a certain structural failure, the extent of rectification works will depend on the cause of failure and there are many causes; tree roots, inadequate steel reinforcement of concrete strip footings, drainage problems, foundations of fill - the list is extensive. While each construction style have common characteristics of failure, each failure needs to be assessed on a case by case basis for an adequate solution and estimate of repair expenses to be calculated.
A Pre Purchase Building Inspector will look for cracks in brick work and structural walls, they can offer professional opinions of the likely cause of a structural failure where the cracks are visible and will usually offer an opinion on the direction to take. However accurate assessments of the repair costs and structural solution usually require further soil testing and an analysis of the building that is much more specific and detailed. Houses found to have structural failures should not be pursued without significant caution and a complete understanding of the financial expenses, health hazards and time frames of repair.
Article written by Jason Wier B. Eng (Building) principal Inspection Angel 2007.
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