Office · Melksham
Bowerhill · Single garage
Integral garage to home office. New DPM and screed, ethernet, two skylights. 5 weeks.
The unused garage is the cheapest space you'll ever buy.
Most garages in Wiltshire and Somerset are full of bikes, lawnmowers and cardboard boxes — not cars. Converting them adds 12–18m² of usable floor area without planning permission, without losing garden, and at roughly half the per-metre cost of an extension.
The trick is doing it properly. Garages were almost never built to habitable-room standards. Floors are uninsulated, walls are single-skin or have no DPC, and the door opening leaks heat. A bad conversion looks fine for two years and then turns into a damp, cold problem room.
What we typically convert garages into
- Home office — most popular post-2020. Hardwired ethernet, double-glazed window, often a separate door.
- Gym — reinforced floor, proper ventilation, sometimes a heat-pump.
- Playroom / family room — opens through to existing kitchen/lounge.
- Annexe / granny flat — often combined with a small en-suite and kitchenette. Stricter regs apply.
- Utility / boot room — plumbing for washing machine, dryer, sink.
- Extra bedroom — strictest regs (escape, ventilation, insulation).
Integral, attached and detached garages.
Integral (built into the house)
Easiest to convert because they share walls, roof and often the foundations of the main house. Internal access already exists. Usually permitted development on the inside.
Attached (sharing one wall)
Common with 1980s-onwards estates. Conversion involves opening up the shared wall (knock-through) to integrate with the house, plus full upgrade of the external garage walls.
Detached
Trickiest. Often single-skin block walls with no DPC. Detached habitable buildings have additional planning and building-regs implications. Sometimes more cost-effective to demolish and replace with a SIPS garden room.
Damp, foundations and insulation — the three things to get right.
Honestly: every garage conversion lives or dies on these three.
- Damp-proof course (DPC): If the existing slab has no DPM (most pre-1990 builds), we either rebuild the floor with a 1200-gauge DPM, insulation and screed (proper job, ~£3–5k extra) or tank the existing slab. We don't pretend the problem isn't there.
- Foundations: Many garages were built on shallow strip footings (300–450mm). For habitable use, building control may want this verified. Trial holes are part of our quote process.
- Insulation: Walls usually need internal insulation board (50–75mm PIR) plus plasterboard. The roof gets thick PIR between rafters. Floor build-up adds 100–150mm of insulation.
Recent garage conversions.
Annexe · Frome
Marston Lane · Annexe
Detached garage to one-bed annexe with kitchenette and shower room. Foundations underpinned.
Gym · Trowbridge
Hilperton · Garage gym
Reinforced rubber-bonded floor, mirrored wall, electric heater. Quick spec, 3 weeks.
FAQs.
Do I need planning permission to convert my garage? +
Most internal garage conversions fall under permitted development if the external footprint stays the same. Replacing the garage door with a brick-and-window infill usually requires planning if the property is in a conservation area or had PD rights removed. We confirm before starting drawings.
Will my garage need a damp-proof course and proper foundations? +
Older garages were often built with shallow foundations and no damp-proof course in the floor. We dig trial holes to check, and where needed we either tank the existing slab and walls or rebuild the floor with a new DPM, insulation and screed. Honest answer: this is the biggest cost variable on garage conversions.
What can I use the converted garage for? +
Most popular: home office, gym, playroom, annexe/granny flat, utility room, extra bedroom or open-plan extension to the kitchen. Bedrooms and habitable rooms have stricter building regs requirements than utility/office use.
How much does it cost? +
For a typical single-garage conversion to a habitable room, expect £18,000–£32,000 depending on the structural works needed (floor rebuild, new windows/doors), the spec of the finish, and whether plumbing or a new bathroom is involved.
How long does it take? +
A typical single-garage conversion takes 4–6 weeks on site, including any floor rebuild. Adding a bathroom or kitchen extends this to 6–8 weeks.