So, the diagnosis is in, and it’s the worst possible outcome; subsidence. You’re now the proud owner of a building which is slowly sinking into the ground. Warped windows, big cracks, broken plumbing and serious structural damage – you have all of these to look forward to. This is obviously terrible news, but now you’ve got to take action – how should you treat the problem?
When it comes to subsidence, you have two main options. Concrete underpinning and resin injection. Both methods have their advantages and disadvantages, and this article will hopefully point you in the direction of the one which is better suited to your particular situation.
This is the older of the two methods, and there are two types of concrete underpinning. The first basically involves the pouring of concrete into the area underneath the foundations until they are back up to where they originally were. The second utilises concrete pilings – these are like bit nails made of concrete that are sunk into the ground and attached the foundation to hold it in place.
- Established. The fact that this method has been in use for over a century does suggest that it is effective and trusted by contractors and homeowners.
- Can be cheaper, for smaller jobs.
- Requires large scale excavation, which is noisy and disruptive. You will have to leave the premises while work is going on.
- Large vehicles and machinery is needed, increasing costs and disruption.
A much newer method, only having been in use for the last 30 years or so. Resin injection requires small holes to be drilled into the ground near your foundations, and then filled with geopolymer resin. The resin then expands underneath the foundation and lifts it up, back to its original position. It also binds with the surrounding soil, compacting it and ensuring that it cannot shrink or expand, depending on the moisture content.
- Fast. Resin injection is a very quick process. Once the resin has been injected into the holes, it will harden in about 15 minutes, allowing the surface to be used again.
- Little or no excavation required. In most cases, you can stay in your home while the injection process is occurring, minimising disruption to you and your family.
- Small and mobile kit allows access to tight or hard to reach areas.
- The low viscosity of the resin means that it can fill small or awkward areas easily.
- It’s a lower weight solution which puts less pressure on the ground soil underneath.
- If there is a large fissure under the ground, it may take a lot of resin to fill it, so might end up costing more money than first thought.
Clearly, resin injection has several advantages compared with concrete underpinning, including speed, lack of disruption and versatility, but if the area requiring the underpinning is quite small then concrete underpinning could be the cheaper option. Both methods will stabilise the ground underneath your home and keep it from sinking back down again, giving you your home back again.