Steps for Underpinning a Foundation
If a structural engineer or surveyor has assessed the foundation of your house and confirmed that it requires underpinning, they’ll advise you about the underpinning method to use for the particular situation.
Here are the steps involved for most underpinning techniques.
Step 1: Excavation
The process of underpinning starts with excavation. The soil around the foundation is excavated to create space to pour concrete beneath the foundation or for the Melbourne underpinning contractor to insert reinforcing piles or beams.
Step 2: Preparation
In case the method to be applied is mass pour, concrete will be poured through a hole around and/or under the foundation.
Formwork is installed and steel wires are set up for reinforcement. The formwork works like a mold to ensure the poured concrete matches the required shape and size and fits in the exact location.
Step 3: Reinforcement
When doing mass pouring of underpins, properly mixed concrete is poured and given enough time to set in the formwork.
In case piles are to be installed, they’re fitted into drilled holes or driven deep into the soil until they’re anchored on stable soil.
The process of underpinning is started from one corner and done inwards beneath the wall being reinforced.
Step 4: Infilling
The soil excavated in the first step is backfilled as needed and compacted.
Step 5: Repairs
Upon stabilizing the foundation to prevent any further structural movement, repair work can be done in the exterior and interior of the house.
Common repairs include fixing cracks and redecorating. You may also have to fix any damaged paths, garden walls, driveway, patio, and fences. Some home insurances cover the costs of such repairs. Thus, check with your insurer for possible coverage.
Also, remember to ask your underpinning contractor on when to temporary move out before the underpinning process is started and when you can move back in. That way, you’ll easily plan on where to stay before your home is stabilized and safe.
House Underpinning FAQs
What’s the meaning of house underpinning?
Underpinning is a process used to strengthen and stabilize an existing foundation.
How much will underpinning cost me?
The exact cost of underpinning is not standard. This is because every underpinning situation is unique to a specific structure. Also, there may be different reasons that necessitate underpinning.
Besides, there are different underpinning techniques employed and each situation may require the use of a specific underpinning technique.
A structural engineer or surveyor can assess your situation and assist you in approximating the overall cost of underpinning. In case the structural issue is covered in your insurance, then you shouldn’t worry about the cost involved.
When is underpinning required?
There are several reasons that may necessitate underpinning an unstable structure. A foundation can become unstable once it’s no longer able to support a building adequately due to the following reasons:
- The wrong foundation design was used due to errors in soil classification
- The usage of the house has changed, especially after adding an extension that has put excessive strain on an existing foundation
- The soil conditions on which the foundation sits have changed due to wetting and drying often, thereby making the structure to settle.
What does underpinning involve?
Underpinning entails renovating a foundation to strengthen it. It involves strengthening the base soil on which the foundation sits or reinforcing the foundation. There re numerous underpinning techniques used to strengthen a foundation.
Read: The Basics of Stabilizing a Settled Building by Underpinning
