There are a few different methods to underpinning, we use mass concrete piers reinforced with steel. Because the piers are extended down to stable ground they are unlikely to be effected by further soil movement and is a permanent solution. Resin Injection is a new method available, although not considered underpinning it involves injecting polyurethane resin to fill voids which expands and compresses the ground, as the resin is not going to stable ground it is vulnerable to movement and not considered a permanent solution. Often when excavating the piers is when the cause of the subsidence is found, whether it be a broken pipe, tree roots or water table and can be fixed. When resin is used there is no excavation so the cause is often missed and not fixed resulting in further damage.
What is Underpinning?
Underpinning is the method used to stabilise and reinforce the existing foundation of a building. The foundation is extended using piers into stable ground.
Underpinning is usually required when subsidence has occurred, this is the result of Expansion and Contraction of the surrounding soil - Adelaide has highly reactive clay soils.
Expansion and Contraction can happen due to weather changes, Inadequate plumbing, lack of footpaths surrounding the building or large trees.
Other common reasons underpinning is required are poor construction of connecting extensions, soil erosion and Poorly compacted fill - which is commonly seen in newly built homes.
Do I need Underpinning?
The most obvious signs that your home might need underpinning to look for are cracks in walls, small hairline cracks in cornices and walls are generally not an issue, we do recommend taking some photos to help you monitor the growth. (change of seasons is generally when you can expect to see movement.) If you have come across larger cracks, they can normally be found externally at corners or around doors and windows these may need to be inspected by a professional.
Other signs are trouble closing/opening doors or windows, you maybe even be able to see an obvious lean in the floor or walls os the home.
Choosing a contractor.
Choosing the right contractor is the most important part of the underpinning process. When researching contractors you should check licensing, reviews and ask for photos of past jobs.
Underpinning is not as simple as digging a hole and filling it with concrete, we have to consider loads, weights, angles of walls. Underpinning should not be undertaken by anyone who doesn't specialise in the field, it could end up costing thousands more and do further damage to your home.
Ladhams and Sons specialise in Underpinning with years of experience, if you would like to book an inspection call or email to arrange a time.