Building Regulations: the Underpinning

Construction regulations are applicable if the building foundation must be underpinned in its entirety or partially. Regulations define the work as building and the necessary measures to stabilise the structure must be implemented.

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In underpinning, the building’s foundations are lowered. It involves excavating the soil below an existing foundation and replacing it with foundation materials, typically concrete.

It is important to pay attention to the design, methods and safety protocols when underpinning. When not completed properly, underpinning can pose real dangers and cause the collapse or damage of the house.

The following are the most common reasons:

It is possible that the foundations are shifting due to changes in soil or poor soil.

If the decision has been made to modify the building by adding another level above or beneath ground level and the depth or weight (load) is insufficient to support that modified structure.

Plan and carry out the underpinning project with great attention to detail. Normal approval will be needed if you plan to reinforce an existing structure. The preparation of an underpinning structural design, which includes the method to be used during construction is usually required in order to obtain this approval. In order to get approval, the first thing to do is dig a hole near to the existing footings.

Methods and Inspections

The specific method that will be used for underpinning depends on the circumstances. In order to minimize the risk of damaging existing structures, it is important to follow all the instructions provided by the engineers.

A poorly done project can result in damage to your existing home or its collapse. The project should be carried out by experienced professionals in design (such as a structural designer) and building (such as someone with underpinning experience and general construction work).

Commonly, short sections of the underpinning will be completed one at atime. In some cases, depending on the size of the foundation that needs to be stabilized, more than a single section can be completed simultaneously.

Normally, a structural engineer and a building inspector will check the excavation for every section of underpinning before it’s concreted. Because of the possibility that gaps will exist between existing foundations and concrete, filling the excavation will not provide a solid support for the underpinning. For this reason, it is often necessary to use sand-cement packing in the void. An engineer and a building control surveyor may inspect this.

This will depend on each base and is best left to the structural engineer.