Converting a Double Attached Garage

You really should look at the intro. in “single attached garages” before reading this, it covers a few points, particularly regarding garage roofs.

You will also be appraised of the process we are following, regarding the basic job, followed by “add ons”.


The basic job (assuming a pitched roof)

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

A vapour barrier, insulation and dry lining to convert the existing exterior brick (side and rear) walls.

A timber, insulated, plasterboarded stud wall, directly behind both sets of up and over doors.

An insulated, plasterboarded ceiling, with ventilation above.

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

Fit two radiators, four electrical sockets, one central light and switch, skirting boards, architraving around the rear external door if you leave it in and probably a bit of boxing to hide the gas meter.

That will take two blokes on £150 and £100 per day respectively, 13 days, plus the same sparks and plumber, for a day each …….

Labour………………….. £3650.00
Materials…………………£2000.00
Building control………. …£350

Basic Job Total …….£6000.00


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 the old floor (because it’s too high possibly), and lay a new concrete “base slab” before undertaking the described, “basic job” floor work…………..£1400.00

Convert an existing flat roof to a warm roof……..£1600.00

This price takes into account the ceiling and insulation included in the “basic job” price.


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

Bricking up an existing rear door……..£325.00

Putting in a side or rear window ………£700.00.

Removing the garage doors and central brick pier, putting in a new long lintol, laying a new foundation and building a wall and wide window across the front, to “match” the rest of the house.

This price is minus the amount previously included in the basic job for masking the doors. …………..£2100.00

Converting the existing exterior side and rear walls to cavity walls.

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 dry lining the walls…..£400.00

Plastering all the walls and ceiling……….£500.00

Putting in underfloor heating connected to your boiler…………..£750.00

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