Underpinning is a process of extending the foundation beneath a house of a building so as to distribute the weight of the house/building evenly and to make it stronger than before.
Advantages of Underpinning
There are many advantages to getting the house underpinned, here they are:
Preserves Integrity of a house
Underpinning preserves the integrity of your house which has been compromised due to the inefficient work of inexperienced contractors or because a part of the original foundation was resting on marginal land that has the insufficient bearing capacity to hold up the home.
Underpinning opens the hidden mechanics below the house and makes the foundation accessible to inspection and correction.
Makes old foundation new
It is especially advantageous in older homes where older plumbing, electrical components, and insulation systems require replacement.
Water-proofing the systems
Underpinning makes all the components below the foundation safe and waterproof while also prolonging their life
Underpinning saves energy costs, improves foundation strength and also increases the resale value of your house if you plan to sell it in future.
Process of Underpinning
Different types of foundations and problems lying beneath should be dealt with utmost care. And thus, different methods of underpinning depending on the actual situation should be adopted.
Thus, it is necessary to first determine the reason that is making the foundation of your home weak. Majorly, there are six types of underpinning methods that can be employed to treat the foundations. Let’s have a quick look at the step by step process of each of them:
- Mass pouring or mass concrete underpinning
This is one of the traditional methods used by contractors today. It is explained as follows:
- Small boxes are dug with a hand beneath the existing foundation
- Mass concrete is then poured within these boxes
- It results in another strong foundation under the existing one
- The method works well up to 50 feet
- The process involves low cost and it very convenient
- Beam and base method
This is a technically advanced technique of underpinning. In here:
- A concrete beam is constructed below the existing foundation
- Mass concrete bases are constructed at different locations
- The result of the construction is such that the load of the whole building is transferred to the mass concrete bases.
- The design of the beam depends on the configuration of the building
- Pile method
This method is most suitable for places that have variable positions of groundwater and where structural movements are minimum. The process is as follows:
- Piles of 15 meter are constructed of small diameter
- These are then pushed on both the sides of the wall
- Needle beams are placed over the piles that act as pile caps
- This method helps in alleviating the load from the walls. Thus, the existing foundation of the wall is not disturbed in the process
- Expansion resin injection method
This is a modern, innovative and one of the most proven methods of underpinning. The process involves:
- Small holes are first made beneath the existing foundation
- An environmentally-friendly resin is injected into the foundation
- The resin flows down, expands and exerts pressure on the ground, thus compressing the surrounding soil and filling the cracks
- More resin than what is actually required is injected to lifts the house to its original position
- Pre-test underpinning
This method is most suitable for multi-story buildings. It is explained as follows:
- This method is generally used before the underpinning of the house
- In this method, the soil is subjected to a calculated load
- The sunken soil beneath the existing foundation is excavated
- The remaining underlying soil is compacted and compressed by suitable methods
- After compression, a suitable method from the above is then used to underpin the foundation
- Screw piles and bracket underpinning
This method is adopted in areas where regular methods of Underpinning fail. The process is as follows:
- Here screw piles are installed in the foundations
- The screw piles are installed along with underpinning brackets
- The whole inserted structure lifts the building back to its original level
- The load of the whole structure is transferred to the pier and the bracket system
- The method is quick and causes no damage to the surrounding area
Thus, if are planning to get your house underpinned, do go through the above methods and their detailed process so that you can select a suitable underpinning method for your house.