Can you extend on a sloping site? Absolutely! Our expert explains how

modern extension on sloping site
(Image credit: Jeremy Phillips)

If you are wondering how to build on a slope in a bid to extend your home, it is worth bearing in mind that very few gardens make ideal building plots. Common impediments such as trees, drain runs and boundary fences can normally be accommodated at the design stage, but where gardens have a distinct slope there are important extra considerations that need to be taken into account.

The Building Research Establishment (BRE) have identified unstable sloping ground as a major cause of progressive movement in buildings. So to avoid any future risk of cracks appearing in extension walls, when building an extension on this type of plot, deeper stepped foundations will likely be needed. 

Ian Rock

Chartered surveyor Ian Rock MRICS is a director is and the author of eight popular Haynes House Manuals, including the Home Extension Manual, the Self Build Manual and Period Property Manual.

Ian is also the founder of Zennor Consultants. In addition to providing house surveys, Zennor Consultants provide professional guidance on property refurbishment and maintenance as well as advising on the design and construction of home extensions and loft conversions, including planning and Building Regulations compliance.

Ian has recently added a 100m2 extension to his home; he designed and project managed the build and completed much of the interior fit-out on a DIY basis.