Image of stairs leading to a basement

Basement conversions

An apparently simple conversion of an existing cellar can be as complex as a new build.

Basement conversions are increasingly popular. Converted or new basements tend to be used for utility rooms, games rooms, cinemas and other spaces that don’t require natural light – although there are ways to bring light in using light shafts or voids that extend to the floor above.

Who do I talk to first?

You should ideally consult both an architect and a structural engineer on your design, although some engineers can offer a complete design service. In addition to structural considerations, there is likely to be the need for planning approval.

What sort of work is involved in converting or creating a basement?

Whether you are converting an existing cellar or creating a new basement under an existing property, the key is ensuring that the existing structure is properly supported during the work below, as it will undermine the foundations.

An apparently simple conversion of an existing cellar can be as complex as a new build: headroom is often insufficient, meaning the floor needs lowering or upgrading to meet the requirements for habitable space.

To avoid undermining the wall foundations, underpinning is often needed. The new, permanent structure will effectively act as the replacement foundation for all or part of the existing property.

Why is a structural engineer necessary?

An engineering design is required to achieve Building Regulations approval, without which the basement may devalue the property.

Structural design is critical to this work: the consequences of a mistake could cause significant structural damage to your property and your neighbours’ properties too. 

What can I expect the structural engineer to provide and/or guarantee?

The engineer should be able to provide design and drawings suitable for Building Regulations approval of the structure and construction.

Depending on experience of the practice, an engineer may be competent to provide the complete design to meet the full Building Regulations and allow construction of all relevant parts.

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