Rear extensions for terraced houses

What is different about extending a terrace?

Everything comes through the house unless there is a rear alley, so we protect the hall and plan deliveries in small loads. Both neighbours are usually adjoining owners under the Party Wall Act in England and Wales, and the boundary walls often need underpinning or a new footing.

Planning is usually straightforward for 3 metres, but many Victorian terraces sit in conservation areas where permitted development is restricted, so we check that before the first drawing.

How much does a terraced house extension cost?

Allow £2,050–£3,300 per square metre including VAT for a standard specification. A 3 m × 4.5 m extension typically comes to £27,500–£44,500, and 3 m × 6 m to £37,000–£59,500. Access through the house and two party walls are the main reasons terraces cost a little more per square metre than semis.

Do you need planning permission?

In England a single-storey rear extension can often be built under permitted development: up to 3 metres beyond the original rear wall of an attached house, or 4 metres on a detached house, no higher than 4 metres, with eaves no higher than 3 metres if any part is within 2 metres of a boundary.

What about the neighbours?

The Party Wall etc. Act 1996 applies in England: you serve notice two months before work to a shared wall, and one month before digging foundations within 3 metres (or 6 metres for deeper foundations) of a neighbour's building. Neighbours can agree in writing; if they dissent, surveyors agree an award.

What is included?

• Access and protection plan through the house
• Party wall notices to both sides
• Boundary footings and underpinning where needed
• Skip and parking licences
• Single-storey or side return design
• Rooflights to keep the middle of the house bright
• Rainwater routed without crossing neighbours
• Building control sign-off

Guide prices by region

Per square metre of new floor, including VAT, standard specification.