How much does a garage conversion cost? Take the quote apart, line by line

How how much does a garage conversion cost works

1. Ask for the schedule, not the total. Floor, external wall to the door opening, insulation to walls and roof, window or door, electrics, heating, plaster and finishes, and the building control application. Eight lines. A quote that gives one number is not comparable with anything, and a quote missing two of those lines is not cheaper, it is shorter.
2. Find out what the floor line assumes. This is the line that moves most. Overlaying the existing slab with insulation and screed is one price; breaking it out because there is no membrane, because it falls to the door, or because it is too low to raise, is another entirely. The quote should say which it has assumed and what the rate is if the assumption fails.
3. Check whether building control is included. The application fee, the inspections and the completion certificate are a real cost and a real programme item. Some builders include and manage it, some leave it to the owner, and the two quotes look different for that reason alone. The certificate is not optional.
4. See who is doing the elevation. Filling the door opening well is the difference between a conversion that reads as part of the house and one that reads as a filled garage. Brick matching, the size and position of the new window, and whether the new wall sits flush or set back are all decisions, and a quote that treats it as blockwork and render has decided one of them for you.
5. Ask what happens to the heating. A radiator on the end of a long run in a room that used to be outside is not a design. Whether the system can carry another emitter, whether the pipe run is realistic, and whether electric or a separate unit is more sensible is a question for whoever prices it, and the answer belongs in the quote rather than on site.

Insurance and paperwork

Common questions

How much to convert a garage, and why do quotes for the same one vary so much?

Because the scope varies. The floor, the building control application, the elevation work and the heating are the four lines that are most often absent from a low quote, and each of them is real money that appears later.

Should I use a specialist or a general builder?

Either can do it well. A specialist has the sequence off by heart and often manages building control as routine; a good general builder is more flexible about combining the work with something else. What matters is the schedule they quote from.

How long does one take?

A straightforward single garage is usually a few weeks of work rather than months, and the programme is driven by the floor and the drying time of any wet trades. Building control inspections have to fall at the right points, which is another argument for whoever manages them being named.

What should garage conversion costs include?

Eight lines: the floor, the external wall to the door opening, insulation to walls and roof, the window or door, electrics, heating, plaster and finishes, and the building control application. A quote that gives one number is not comparable with anything, and a quote missing two of those lines is not cheaper, it is shorter.

What moves the cost of converting a garage into a room most?

The floor. Overlaying the existing slab with insulation and screed is one price; breaking it out because there is no membrane, because it falls to the door, or because it is too low to raise is another entirely, so the quote should say which it has assumed and what the rate is if the assumption fails.

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