Terraced houses make up a large proportion of residential property in Greater London, and their owners regularly want to extend to create more space without moving. Whether the goal is a larger kitchen, an additional bedroom, or a home office, extending a terraced house is very achievable but it requires careful planning given the particular constraints of this building type.
The most common extension type for a terraced house is a single-storey rear extension, typically built on the original garden footprint to enlarge the ground floor living and kitchen areas. Under permitted development rights, a single-storey rear extension can be built without a full planning application provided it does not extend more than three metres beyond the original rear wall of the house in a terrace, does not exceed four metres in height, and satisfies other conditions around materials and site coverage. For extensions between three and six metres, a Householder Prior Approval application under the Larger Home Extension Scheme is required.
Party wall matters are particularly important for terraced houses. Because you share walls with neighbours on both sides, any structural work that affects or is adjacent to a party wall will trigger the Party Wall etc Act 1996. This means you must serve formal party wall notices on your adjoining neighbours at least two months before work begins on the party wall itself. If neighbours consent, the notice is sufficient. If they dissent or do not respond, party wall surveyors must be appointed to produce a party wall award.
Foundations are another important consideration. In London, the clay subsoil expands and contracts seasonally, which means foundations for extensions need to be taken to adequate depth, often between one and two metres. A structural engineer should advise on foundation type and depth based on a review of site conditions.
For terrace extensions, drainage routing can also be complex. The existing drains often run beneath or close to the proposed extension footprint, and any build-over of a public sewer requires prior approval from Thames Water. Early investigation of drain positions saves surprises during excavation.
The connection between the existing house and the new extension is a critical design decision. Bi-fold or sliding doors are popular for opening the rear of the house onto the garden, but the structural beam required to span the opening can be substantial and should be sized by a structural engineer. The wider the opening, the larger the beam required.
RCB Design & Build carries out terraced house extensions across London, managing the full design, planning, party wall, structural, and build process. We ensure the right professionals are in place at each stage and that the project runs smoothly from the very start.