Eccentric foundation


Eccentric foundation


Eccentric foundation

When a wall is built on the centre of a foundation then the foundation bearing pressure will be uniform. However, if the wall is built off centre, then this will not be the case. This is called an eccentric foundation.  Sometimes this can’t  be avoided.  If a building is built on a boundary, then the foundation will most probably need to be eccentric.  This can in turn result in very high bearing pressures beneath one edge of the foundation.  The solution is to design the foundation for this condition.  This will normally result in a larger foundation being needed when compared to a centrally loaded foundation.

Because of this, Building Control will often ask for calculations for this type of foundation.  For single storey loads the foundation width may well turn out to be the same as normal.  However, if there are two or more storeys then this is unlikely to be the case. In these cases, a wider foundation is most likely to be needed.

We need the following information to design an eccentric foundation

architectural layouts and elevations of the property / extension

the distance between the outside of the wall and the boundary (if it is not on the boundary)

details of the ground conditions at the site

Design information

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

The calculations provided will be suitable for Building Regulation approval.

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

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