Underpinning is a technique that reinforces and strengthens foundations that have undergone settlement or have moved due to seismic activity or unstable soils. This procedure stabilises damaged foundations and halts structural damage to crucial parts of the house such as the walls, floors, roof and basement. Before commencing foundation underpinning, take the following steps to ensure the success of the project.
Conduct a preliminary assessment
A preliminary assessment is a surface-level investigation that ascertains the possibility of foundation damage. The most common signs of foundation damage are structural cracks, sticking doors and windows, drainage issues, basement leaks and sagging flooring. However, these signs can also be due to other problems not related to the foundation.
For example, hairline wall cracks may occur because of poor installation. However, if the cracks are deep, they may be due to foundation problems. A professional can conduct a visual walk-through of your house to ascertain whether there is foundation damage.
Carry out an in-depth investigation
Once there's evidence of foundation damage, the next step is to conduct a foundation inspection. You may require the services of structural engineers and ground works contractors to conduct this investigation. During this process, you need to establish the following issues:
- Size and depth of the foundation
- Condition of underlying soils
- Extent of foundation damage
- Site factors such as drainage and slope
- Cause of foundation damage
Understanding these issues helps your contractor to come up with viable underpinning techniques. For example, if you have a shallow foundation on expansive soil, the soils may have caused the damage. These investigations also help to come up with an accurate budget. For example, if a large portion of the foundation has moved or settled, you will spend more to fix it than if the damaged section is small.
Determine the best underpinning method
Underpinning is the go-to method for fixing foundation issues. However, different techniques are suitable for different situations. Factors such as budget, foundation access, depth of existing foundation and existing soils can determine the preferred method. For example, where the foundation settled due to soil clogging and expansion, the pile method would be an excellent choice.
The pier and beam method is ideal for shallow to medium-depth foundations. If you want to increase the load-bearing capacity of the foundation for purposes such as building an extra storey, the cantilever needle beam technique is the best choice. If you have a tight budget, you can opt for the pit or mass concrete method of underpinning. Your contractor will also consider the proximity of your home to other structures and whether the chosen technique can adversely affect soil stability.
When done promptly, foundation underpinning can save you from costly structural repairs. Work with your contractor to assess the above issues and formulate a practical restoration plan for your foundation.