Basement Conversions — London’s Premium Underground Space
London’s inner-city property boom has made basement conversions one of the most sought-after home improvement projects in the capital. In areas like Kensington, Chelsea, Maida Vale, and Islington — where gardens are small and planning for above-ground additions is restricted — going underground is often the most practical way to add significant space.
Prime Loft carries out full basement conversions including underpinning, waterproofing (tanking), and complete fit-out. We project manage the full process from structural engineering through planning and into build — with a fixed price and 10-year structural warranty.
What Could Your Basement Become?
Cinema Room
The most popular basement use in London — a fully soundproofed, climate-controlled private cinema.
Home Gym
Premium fitness space with rubber flooring, mirrors, and specialist ventilation.
Library & Study
A quiet, light-controlled space for reading, study and focused work.
Wine Cellar
Temperature and humidity-controlled storage for wine collections — the ultimate luxury addition.
Music Studio
Fully soundproofed music or recording studio — basement level eliminates structural sound transmission.
Additional Living
Guest suite, self-contained flat, or teenage den — prime additional living space.
Basement Conversions — FAQs
Basement conversions in London typically start from £70,000 and can reach £200,000+ for complex projects. The key cost drivers are the extent of underpinning required, the waterproofing specification, and the level of fit-out.
In most cases, yes. Basement conversions require planning permission in most London boroughs, particularly where they extend beyond the existing footprint. Conservation areas have additional requirements.
A basement conversion typically takes 12–20 weeks on site. The pre-construction phase — structural engineering, planning approval, Building Regulations — adds 12–20 weeks.
Book Your Free Survey & Fixed-Price Quote
No obligation. No pressure. The exact price for your conversion — guaranteed.
Book Free Survey or call 0208 123 4567