HOUSE CRACKING - Supadiverta - syphonic rainwater diverter

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HOUSE CRACKING

We originally developed the Supadiverta to deal with this

House cracking is a serious problem and the often expensive repairs are rarely covered by household insurance. Most house cracking problems are claimed to be related to diminished subsoil/clay moisture content during extended periods of below average rainfall.

Other causes of house cracking may be attributed to:

  • Large trees growing too close to the house.

  • Excessive subsoil/clay moisture content. This is often unseen and may be traced to a leaking pipe or run off from a neighbouring property, often driveways or paved areas that follow an underground water course.

  • Foundations poured in reactive soil during abnormally wet or dry conditions.

  • Settlement of new extensions.

  • Nearby earthworks and construction.

  • Earthquakes.


Householders with concerns about low subsoil/clay moisture content related brick cracking issues are strongly advised to seek onsite professional advice from a qualified geotechnician or an architectural firm with expertise in this field.  Geotechnical assessments are a specialised discipline and your house is a valuable asset. Would you trust a chemist to operate on you or a plumber to build your house? How about a builder giving you geotechnical advice?

The cause and treatment of house/brick cracking can be complex and an onsite geotechnical assessment generally includes the sampling of subsoil moisture content from several locations. This will determine the areas in need of rehydration if low subsoil/clay moisture levels are assessed as being the cause of the cracking and subsoil/clay rehydration assessed as being the appropriate solution.

Treatment most often involves the drilling of small diameter holes lined with Ag pipe into the clay base. The subsoil moisture levels are then monitored afterwards by the householder checking moisture levels with a Neutron Moisture Meter (NMM) and slowly feeding water down the pipes as required. In some instances, rehydration through a drip system may suffice but in cases of severe structural damage, a geotechnical engineer may advise of other courses of action or referrals.

Drip feed rehydration uses natural phenomena known as matric suction. This occurs when dry soils (with high matric suction) draw moisture from surrounding wet soils (low matric suction) to equalise moisture content. For this reason, a drip hose does not need placing next to the house to be effective and generally should not be placed within one metre of the foundations.

Matric suction also increases a soil’s shear strength as in the case of the high matric suction under trees planted on a slope helps to stabilise the soil. It is also the reason large trees do not need to extend their roots to the house foundation in order for the house to suffer from foundation movement.

The cause of brick cracking is not always where the cracking has occurred; it could be on the other side of the house! Get it wrong and the problem could become worse. Apart from risking treating the wrong area, conditions created by inappropriate watering may also encourage termites, dry rot and rising damp.

One or more SUPADIVERTAS redistributing harvested rainwater through a drip system can be a vital component of a professional geotechnical management plan that addresses domestic low subsoil moisture content issues.

Recommended reading is available at www.structuraldesigns.com.au (Canberra) through their FAQ on Cracking in Brickwork (found under masonry).

 
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