Whether you are buying your first or your tenth home, its always exciting buying a new house. However its important to not get too excited about your new home before you have done your due diligence. There are quite a number of checks you need to do – including that your your lender is happy to give you that mortgage – but one that is often missed is a geotechnical report.
In some areas of the country slope stability and ground subsidence can be a real issue and its important to make sure that you proposed purchase is not subject to either! Many newer sub divisions are created by bulldozing existing hills or cutting geotech report christchurch building sites out of the hillside itself. There is nothing intrinsically unsafe about this practice but its important that the correct engineering calculations were made at the time so that the house is not in damage of being damaged or, at worst, demolished by the retaining wall failing to support the hillside behind it.
Substance is a gradual process where the land which a home was built on was not compacted adequately prior to the house being constructed. Subsidence is usually a gradual process and you may be able to see cracks in the house’s floors, walls or even outside hard surfaces such as patios and drive ways.
In contrast a slope stability problem you may not know about until there is a landslip. Landslips are occasionally slow and gradual – but more likely are triggered by something, an earthquake or a prolonged period of heavy rainfall are common causes of landslips. It is a great deal more difficult for a layman to work out whether a house could be at risk from landslip.
If you are looking at a property with a significant retaining wall or cut slope near it there are a couple of things you can do to minimize your risk. First you can check with your insurance company to see if they have a premium loading for the property or area. If the area has been the source of a higher than normal number of claims this is a hint that you should proceed with a specialist engineering report.
Even if your insurer doesn’t have a problem this doesn’t mean there may not be one. If you can see evidence of rock or mud falls from a cut slope – or notice that a retaining wall is bulging or seems to be under stress – seek specialist advice before committing to the property!