Average garage conversion cost, and the three variables that decide yours

How average garage conversion cost works

1. Integral, attached or detached. An integral garage is inside the house's footprint, already has walls shared with heated rooms and is the cheapest to convert. An attached garage shares one wall. A detached garage shares none, needs its own heating and services run to it, and is effectively a small building conversion. Those three are different prices for the same floor area.
2. Whether the floor can stay. If the existing slab is sound, at a workable level and can take an insulated overlay, the floor is a modest line. If it has to come out because there is no membrane, because it falls to the door or because raising it would kill the head height, it is one of the largest lines in the job. This single question moves the total more than any finish decision.
3. How far the services have to travel. A garage next to a kitchen with the consumer unit on the shared wall is a short run. One at the end of a detached drive is a trench, armoured cable and a separate arrangement for heat. The distance is fixed by the house and it is not negotiable.
4. What an average is actually averaging. Published averages mix single and double, integral and detached, shell and finished, with and without building control. Before using one, ask which of those it contains, and if the answer is not available then the number is a headline rather than a guide.

Insurance and paperwork

Common questions

Is there a typical figure worth quoting?

This site does not publish one, because the three variables above move the answer by more than any average's spread and a figure printed on a page goes out of date while the variables do not. What is worth having is the schedule and three quotes against it.

Does the finish change the average much?

Less than people think. Flooring, decoration and joinery are the visible half and the smaller half; the floor build up, the opening and the services are the invisible half and the larger one.

Which garage is the cheapest to convert?

An integral single garage with a sound slab at close to house level, next to the consumer unit, with no parking condition on the deeds. Each of those that is not true adds a line.

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