Your house probably rests on a concrete slab in the earth, which provides a stable base. However, sometimes this slab can shift unevenly to stress the building. You then may see cracks in the walls or notice that windows and doors stick in their frame when you try to open or close them. Two common approaches to residential underpinning are explained below to help you work out your options.
Reinforcing the Concrete Slab
Sometimes an existing foundation can struggle because a second story has been built on top as an extension. In these cases, an expert may advise you to bolster the existing concrete slab. They'll pour supplementary concrete around the sides or below the foundation. Another option is to support the slab from underneath with long concrete pilings sunken into the earth. However, getting at the foundation will require a lot of excavation so the contractors can gain access. Thus the process will be relatively disruptive.
Treating the Soil
Another strategy is to reinforce the soil around the concrete slab rather than buttressing the slab itself. This technique involves injecting resin into the dirt, which will expand and clump together to create secure soil for the foundation to sit within.
This solution may be best if the problem arises from unstable soil. For example, you may experience flooding or another natural disaster, or the instability may be due to the soil type. A resin injection process is less invasive than pouring concrete, as the resin is bored into the earth, so less excavation will be required.
Residential underpinning experts will need to investigate your home and its structure to determine the cause of the foundation problem. They may hire a geotechnical engineer to assess the soil and be guided by their advice. Alternatively, you can hire an engineer and provide their report to underpinning experts when you're ready to get quotes.
Thus, there are two basic underpinning methods for a home. One approach involves pouring extra concrete around the foundation to build up its mass and make it stronger. Another strategy is to treat the soil so that it cradles the foundation more securely without shifting. The resolution depends on the origin of the problem, whether it's due to unstable ground or an inadequate foundation. If you notice cracks appearing in your walls or ceiling, or the doors and windows seem out of alignment, you should contact an expert promptly, as the problem won't resolve itself.