Cellar conversion cost, and why the headroom decides the size of the job

How cellar conversion cost works

1. Measure the headroom before anything else. A cellar with enough height under the joists for a habitable room is a fit out. One without it needs the floor lowered, which means underpinning the walls in sequence with temporary works and a structural design, and that turns a modest job into a major one. Twenty minutes with a tape decides which project you have.
2. Understand what a period cellar is made of. Brick walls straight into the ground with no membrane, a floor of stone flags or lime concrete, and often a coal chute or vaults extending under the pavement. That construction breathes, and sealing it badly moves damp somewhere else in the house rather than removing it. A designed cavity drain system that lets the wall stay wet behind it usually suits these better than a barrier.
3. Check what the cellar is currently doing. Many carry the gas meter, the electricity intake, the stopcock and a run of pipework, and several have the only access to the space under the pavement. Relocating an intake is a utility company job with its own timescale, and it belongs in the programme rather than in a surprise.
4. Light and escape decide the use. A cellar with a light well or a pavement light can be a room. One with neither can be a utility, a store, a plant room or a gym, and it cannot be a bedroom without an escape route. The use follows the light, and pretending otherwise produces a room nobody uses.

Insurance and paperwork

Common questions

Is a cellar conversion cheaper than a basement conversion?

Normally much cheaper, because the excavation and the underpinning are the expensive half of a basement project and a cellar conversion avoids both. Once the floor has to be lowered the two converge.

Will converting the cellar cause damp upstairs?

It can, if the work seals a wall that was evaporating moisture into the cellar and pushes it elsewhere. That is an argument for a designed system and for somebody looking at the whole house rather than at the room being converted.

Can I keep the coal vaults?

Sometimes, and they are usually under the pavement, which is often the local authority's land rather than yours. Using them for anything, or altering them, is a question for the highway authority before it is a question for a builder.

Registered contractors by region

• Registered roofers in the East Midlands postcode area
• Registered roofers in the East of England postcode area
• Registered roofers in the London postcode area
• Registered roofers in the North East postcode area
• Registered roofers in the North West postcode area
• Registered roofers in the Scotland postcode area
• Registered roofers in the South East postcode area
• Registered roofers in the South West postcode area
• Registered roofers in the Wales postcode area
• Registered roofers in the West Midlands postcode area
• Registered roofers in the Yorkshire and The Humber postcode area