Converting half a double integral garage

So……. now we’ve got a “2 car wide” garage but the whole thing is still within the “footprint” of the house, i.e. there are still rooms above it.

What you want to do is create a room in the half nearest the house and leave the rest as a junk……sorry, garage.

So, just like before, let’s price for the most basic job you can do and build up from there. Unfortunately you will have to look at our article… “Job 1 etc” to get the full picture.


The basic conversion job

A damp proof membrane, insulation and screed, to create a new floor on top of half the existing concrete one.

A correctly insulated, fire protected, timber and plasterboard stud wall built right down the middle.

A correctly insulated, plaster boarded stud wall, directly behind the up and over door. (We’re assuming there are 2 doors, 1 for each side).

A plasterboarded ceiling.

No plastering, just tape and fill the joints between the plasterboard and paint the room, (including the untouched internal house wall).

Fit a radiator, two electrical sockets, a central light and switch, skirting boards, architraving around the door and probably a bit of boxing to hide the gas meter.

That will take two blokes on £150 and £100 per day respectively, 7 days, plus a sparks and a plumber for a day each.

Labour: £2150.00
Materials: £950.00
Building control: £350


Basic Job Total: £3450.00 give or take, exactly the same as the single garage job!


The following prices are in addition to this basic job.

Maybe you also have to:

Create a new flush internal door from the house: £550.00

Actually dig out half of the old floor (because it’s too high possibly), and lay a new concrete “base slab” before undertaking the above, “basic job” floor work: £1000.00


Or, if you want to spend a bit more how about:

Removing the garage door, putting in a new foundation and building a wall and window across the front, to “match” the rest of the house.

This will be a bit of a must, or you will end up with a windowless room!

This price is minus the amount previously included in the basic job for masking the door:£1300.00

Building an insulated cavity wall down the centre rather than a timber stud wall.

This price includes laying a foundation (which would be done during the floor slab conversion).

We have also deducted from this price, the amount previously included in the basic job for building the stud wall: £350.00

Plastering all the walls and ceiling: £400.00

Fit underfloor heating connected to your boiler: £550.00

This price is minus the amount we included in the basic job for fitting a radiator.