BRANDON offers a complete range of professional underpinning services to businesses and homeowners in London and the South East of England.
We offer a full range of underpinning services including:
At Brandon Groundworks, we are experts in all types of underpinning for commercial and domestic properties. With our underpinning services, your property will be strengthened and its foundations reinforced for many years to come.
When underpinning is required
A crack in your building does not necessarily mean underpinning is required. Sometimes a crack occurs due to poor quality of building materials or excessive moisture, and not because of a faulty foundation.
So, if you’re wondering whether your property requires underpinning, here are occasions when it’s necessary.
Underpinning is required when;
- You need to add building storeys, either above or below ground. Since the new construction will put pressure on the structure, it’s important to ensure the foundation is strong enough to withstand this new load.
- Subsidence has occurred. A change in the condition of the soil where your property stands could lead to a foundational move. This then leads to the building sinking or shifting. In these situations underpinning services can help to correct the problem.
- Nearby building construction has resulted into an alteration in the stability of the ground and a weakening foundation
- The original foundation was not strong enough and is now unable to withstand ground changes. This can be seen through wide vertical cracks on your building walls.
- There is a change in building usage and the soil on which your property stands begins to shift
- Your building footings have clearly been affected, either by a downward or sideways movement. This is common with buildings constructed on loose soil.
How is underpinning done?
Now that you know when underpinning services are required, let’s look at the actual process. In general, underpinning can be done either by increasing the depth (vertical) or widening the foundation area. There are various methods of carrying out this procedure and each is unique to the project and type of damage
Mass Concrete Method
Also referred to as the Pit Method, Mass Concrete underpinning is the most common of all methods and the oldest. The process involves the digging of pits along the outside wall of the building at predetermined intervals and depth, below the existing foundation
After a quick examination of any potential problems, the pits are then filled with concrete, leaving enough space for dry packing later. Dry packing helps to distribute the weight of the building and jolt a sinking structure back up.
Mass concrete underpinning is used in buildings where the original foundation was built on shallow ground. It is a more cost effective method as there is less machinery used in excavations.
Base and Beam Underpinning
This underpinning method is more of an alternative or upgrade to the Mass Concrete method. It involves the insertion of a single concrete beams underneath the existing foundation to add support.
Instead of pouring concrete into open trenches like in Mass Concrete, Base and Beam underpinning uses steel bars for stronger reinforcement. The process involves the digging of pits along the outer wall and in predetermined intervals, dropping steel frameworks into the pits, and then filling them with concrete.
The result is concrete beams that add support to existing foundations and hence a stronger structure. This underpinning method is perfect for buildings that need additional stories or that require a change in structural usage. It is used in both shallow and deep foundations.
Pile and Beam Underpinning
This underpinning method is common for structures with limited access and requiring deep foundations. The process starts by digging a hole below ground and through the wall of the existing foundation. This hole is made to accommodate a horizontal concrete needle beam to help in load distribution.
Piles are then installed on opposite sides of the hole or either side of the foundation wall with steel framework for reinforcement. The piles are then connected to each other with the needle beam running through the hole in the wall, firming up support.
Concrete is then added to fill gaps and add support to the beam. This method is used to transfer
current load from the original foundation to a more stable and reinforced platform.
Our Safety Procedures
In any construction project, it is important to be prepared for any eventuality. And underpinning is no different. Since the work is done under the ground a building stands on the chances of collapsing, plumbing accidents and further damage need to be taken into account.
That’s why at Brandon Groundworks, we ensure our underpinning services adhere to all CDM (Construction Design and Management) regulations. In addition, we ensure the following;
- To conduct a thorough inspection before excavation begins
- Evaluate the type of soil and foundation depth to decide the best underpinning method
- Inspect pits for any potential instability and conduct a general ground assessment
- Plan and enforce health and safety policies in all underpinning procedures
- Use highly qualified personnel for each project