Basement design




Basement design

Where space is at a premium, basements can be very useful. Whilst basements are expensive to build, in areas with high property prices they can still be cost effective.

Planning restrictions can also sometimes limit the height of the building above ground level.  Therefore, building below ground level may be the only other option to create enough space.

Basement walls act as retaining walls. However, if the ground floor is a concrete floor, the support it provides will help to restrain the walls.  Therefore, this enables a more economic wall to be designed.

The walls may be designed using masonry or concrete.  Reinforced masony is generally the best and cheapest way to build the walls.  It is cheaper to build because there is no need to shutter the walls.  Reinforced concrete walls are normally only needed if the basement is deep.

Our basement design also includes the design of a reinforced concrete raft foundation.  This will allow a full external tanking system to be used.


We do not provide waterproofing details as part of our design.  These details should be provided by your Architect, or you can use a specialist contractor to carry out this aspect of the work.  In either case all basements should be waterproofed even if there doesn’t appear to be any groundwater present.  At some stage in the future there most probably will be. Once the basement is built it can be very difficult to fix any leaks.  There are other ways of keeping the basement dry, such as using an internal drainage system.  With this system, the walls are allowed to leak and the water is drained to a sump.  This can then be pumped out.

Our basic basement design does not included preparing a detailed bending schedule for the reinforcement, but this can be added as an option if you need one.  These are not normally needed for a Building Regulation application.

Please note we cannot design basements beneath an existing building, because this would require regular site inspections to be made.

We need the following information to design a basement

architectural layouts of the basement and any walls above it

the internal floor to ceiling height of the basement and the relative level of the outside ground

the position of any site boundaries and any adjacent buildings

information on the site ground conditions

Design information

All designs are carried out in accordance with BS 8110, BS5628  and BS 8004

The calculations provided will be suitable for Building Regulation approval. 

You should satisfy yourself that the excavation for the basement will not undermine any adjacent foundations or neighbouring ground.

Excavations may fall under the Party Wall Act.  Please seek specialist advice.