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IG Building
Service

Basement Conversion & Fit-Out

From damp cellar to finished living space — structure, waterproofing, insulation, M&E and fit-out delivered by one team.

Turn wasted space into living space

Thousands of London houses sit on cellars and half-basements that are used for nothing more than storing paint tins. A basement conversion in London turns that space into a home office, gym, cinema room, utility room or guest suite — usually without planning permission, because the volume already exists. From a Victorian coal store to a full-height lower ground floor, a cellar conversion is normally the cheapest habitable square metre you can add.

We deliver the whole conversion with one team: structural alterations, waterproofing, insulation, electrics, plumbing, ventilation and the finished fit-out. One contract, one point of responsibility.

What a conversion involves

  • Survey and design — headroom, access, damp and structure assessed honestly before you commit
  • Structural works — floor lowering, underpinning and steel work where headroom needs to be gained
  • Waterproofing — a cavity drain or tanking system designed for habitable use (we are Delta Membranes and Wykamol certified)
  • Building regs compliance — insulation, ventilation, fire escape and ceiling heights all signed off by building control
  • Full fit-out — flooring, walls, lighting, bathrooms and joinery to a finished, decorated standard

New basements too

If your house has no existing cellar — or the existing one is too shallow — a full basement excavation creates the space first, and the conversion finishes it.

Wondering about money? We’ve written honestly about what drives the cost of a basement in London. Then have a look at the finished spaces in our work section and request a free site visit — we’ll tell you what your basement could become.

Planning a basement project? Let's talk about it.

A free, no-obligation site visit and quote. We'll tell you honestly what's possible under your property — and what it will cost.

Get a free quote