Basement conversions in Wandsworth

The properties we see in Wandsworth

The Tonsleys are 1850s–1870s two-up two-down cottages: solid-walled, almost no floor void, and with lath-and-plaster ceilings, which makes them the most difficult properties on our patch to run services through. Southfields is a large 1900s grid of substantial Edwardian houses, mostly intact as family homes, with generous voids and logical layouts — much easier to work in. Earlsfield is smaller Victorian terrace, heavily converted to flats. The riverside developments are post-2010 with three-phase supplies, heat networks and management companies.

Planning in Wandsworth

Wandsworth is a comparatively permissive authority, and much of the Southfields and Earlsfield stock retains permitted development rights. Conservation areas apply around Wandsworth Common and parts of the Tonsleys. Riverside apartment blocks bring lease and management-company consent into play, and several require a permit to work and out-of-hours restrictions that materially affect the programme.

What basements involves

Converting an existing Fulham cellar costs £2,500–£4,000 per square metre; digging a new basement under the house is £4,500–£7,000 per square metre once underpinning and structural work are included. Hammersmith and Fulham restricts basement development, so the planning position matters more here than the build cost.

Consider this if

• There is an existing cellar that is damp and unused
• You have run out of ways to extend up or out
• You want a media room, gym or guest suite
• The house is in a conservation area where extending is restricted
• You need a utility and plant room to free up space above
• The garden is too small to lose to a rear extension

What's included

• Honest feasibility on planning and ground conditions before design
• Structural engineer and underpinning design
• Party wall awards with both adjoining owners
• Full tanking and waterproofing to BS 8102 with a guarantee
• Sump and pump systems with battery backup
• Natural light solutions — lightwells, sun pipes, glazed link

The standard we build to

Waterproofed to BS 8102 with a designed drainage system, and structurally designed by a chartered engineer with party wall awards in place before excavation begins.

For the full write-up on basements — costs, timescales, certification and the questions people ask most — see our basement conversions page. The prices and standards are the same wherever we work.