Older buildings were designed to different standards than what are followed today. It is highly likely that your home doesn’t have any foundation or very few foundations. Such a building structure increases the risk of various problems such as flooding, moisture buildup, and even underground gas emissions. The old building can settle down and may not be secure any longer. It will also prevent you from adding new structures such as additional storeys. This is where professional underpinning work can come to the rescue.
What is Involved in Underpinning Work?
Underpinning involves a wide range of methods for re-supporting your building’s foundation. It is performed in a wide range of scenarios. Sometimes the foundation system of the building has been compromised. Other times, there is a need for foundation support to be transferred to a deeper level to allow projects that would otherwisecause damage to the structure and movement of foundation.
As a construction project, Underpinning comes with its set of potential risks. Professional underpinninginvolves proactive implementation of best practices in design and construction.The basic steps involved in the process include:
- Soil analysis
- Creating support for the structure
- Conducting excavation
- Conducting formwork and concrete work
- Creating drainage for the new foundation
- Pouring concrete slab
Types of Underpinning Work
There are different types of underpinning methods. The choice of the right one will depend on your building’s structure and the issues you are facing. All these methods follow similar goals of extending your existing foundation and laying over a stronger soil stratum. The result is distribution of the load over a larger area.
1. Mass concrete underpinning method (pit method)
This is the traditional underpinning method where the old foundation is extended up the stable stratum. Controlled soil excavation under the foundation is done through stages. Once the strata is reached, this excavation is filled with concrete.
2. Pier/Beam Underpinning
Also known as base and beam method, it works with most types of ground conditions. Reinforced concrete beams are used to transfer the weight of the piers or concrete bases. The depth and size of the beams depend on the applied weight and the ground conditions.
3. Cantilever Needle Beam Technique
This method takes the pit method to the next level. It is usually used when the foundation extension is required only on a single side. Key advantages of the cantilever needle beam method include:
- Single side access
- Faster results
- Higher weight carrying capacity
4. Mini Piled Underpinning
When the loads have to be transferred to a strata that is more than 5m away, the mini piled underpinning method is used. It is more suited for foundations with:
- Restricting access
- Variable nature of soil
- Has environmental pollution issues
5. Pile Method
Piles are driven on both sides of the wall supporting the foundation. This involves a pin penetrating through the wall and connected to the piles.This technique is more suited where there has been soil settlement because the soil has a clay-like form or there is water clogging.
6. Pre-Test Method
This underpinning technique is used more often for pad or strip foundation. It is a preferred method for buildings with as 5 or more storeys. The subsoil is compacted and compressed within the new excavation level. This process involves lesser disruptionand noise.
Underpinning is a complex construction work and requires the involvement of a specialized professional service. It is also important to meet latest safety regulations. This is why it is best to hire the services of an experienced contractor for completing the task.The company should specialize in underpinning work for the type of property and conditions you have.