New home beside an existing house

The project

This Woodford Green project forms a new one-bedroom house alongside an existing home. The brief covers the structural design of the new dwelling and a planning fire safety strategy, with particular attention to where the new house meets the old one. Building a home directly alongside an existing house is a common way to add housing in established streets, but it brings the new structure into close contact with a building that is already occupied.

The foundations, the adjoining wall and the way loads are carried all need to work without affecting the house next door. Existing houses in this part of north-east London sit on foundations that were designed for their own loads, not for excavations beside them. That makes the interface between old and new the most important part of the design, rather than an afterthought at the end.

Building a new home against an existing house

Foundations next to the existing house need particular care. Excavating beside an existing wall can affect its support, so the design has to take account of the neighbouring foundations and how the new ones will sit beside them. We design the new foundations to suit both the new home and the house it adjoins, and to be built in a way that keeps the existing wall supported.

At the party wall interface, our checks look at how the new structure connects to or sits against the existing wall, and what that means for both buildings. Work like this often falls under the Party Wall etc. Act 1996, and our guide to the Party Wall Act and structural works explains the notices involved. The structural scheme then covers the rest of the new house.

Planning something similar?

Adding a home beside an existing house can work well, but the interface between old and new deserves early attention. Our party wall structural review is useful when a neighbour or their surveyor wants reassurance that new foundations and walls will not harm their property.