Underpinning is the method of transferring the load of a structure which is showing signs of subsidence or sinking. The load of the structure is transferred to a new support installed in the ground, there are many different methods of underpinning and here at Rhino Piling we offer all types of underpinning. We are more than happy to assess any signs of subsidence or sinking on your property and advise you on the most efficient and cost effective underpinning solution for your case.
Underpinning is also used to create a void below an existing building, or to reinforce an existing building. In the latter example this may be used if you are taking out a supporting wall and need to give the pillars which will be holding the weight of the steel more strength to hold the steel and the load above it.
When is underpinning needed?
• The original foundation is not strong enough to hold the property.
• The properties of the supporting soil have changed over time
• The usage of the property has changed
• The construction of nearby properties such as excavation has affected the foundation of your property
• It is more economical to repair the existing foundation than it is to build a new foundation
What are the different methods of underpinning?
There are four main methods of underpinning used:
Mass concrete fill underpinning
This is the traditional method of underpinning where the site is excavated in sequence and then filled with concrete to reinforce the existing foundation. Upon inspection by building control it is then concreted.
Piled raft underpinning
This method is used when most if not all of the house is affected by subsidence. The ground floor is removed and pockets in the brick work are created and then reinforced by steel, as determined by our structural engineer. Upon inspection by building control, it is then mass filled with concrete creating a new ground floor.
Pile and needle beam underpinning
This method combines mini piling techniques and steel reinforcement, mini piles are installed either side of the affected wall, these mini piles are then connected together with pre-fabricated steel which carries the load of the wall to the mini piles. Upon inspection by building control it is then concreted.
Cantilever beam and needle underpinning
This is similar to the pile and needle beam underpinning system, the difference being that all the work is done from the outside of the property and is therefore more suitable for properties that are lived in as it will not affect the inside of the house.
Mini piling techniques are used to install mini piles to the outside of the property and steel is then used to cantilever the load of the property to the mini pile. Although more mini piles and steel is required in comparison to pile and needle beam underpinning it is often a lot cheaper due to the fact it is all done from the outside of the property.
Why are there so many different methods of underpinning?
Underpinning techniques have developed and become more effective over the years but older methods are still used as and when needed. Also different methods have different advantages and disadvantages. Here at Rhino Piling we can look at the problems affecting your property and advise you on the methods suitable for your property and which would be most effective and cost effective.