Converting A Garage To A Living Space

A garage is probably not high on your list of improvement projects, unless you want to upgrade the door or convert the garage into a new living space.  Garages contain safety hazards and potential structural problems that you should investigate, however.

Even if you do not plan any garage projects, make sure the following items have been taken care of:

  • Eliminate fire hazards.  Move combustible materials, such as paint thinner and gasoline, away from appliances and exposed wood walls.  Incidentally, most states prohibit the storage of more than one gallon of gasoline.
  • Make sure the access to attic space has a door that closes.  The door to the house should have a solid core and should be at least one step above the garage floor.  Make sure that any gas-burning appliances are at least 18 inches off the floor.
  • Minimize structural damage from moisture by making sure the floor slopes toward a drain and that the garage has adequate ventilation.
  • Make sure that all outlets are protected by ground fault circuit interrupters.
  • Correct a garage door that falls rapidly — it is a danger.  Make sure the springs on a garage door have safety bars that prevent them from flying if they break.

Converting A Garage

Where codes allow, a garage provides a means to gain new living space.  In most cases the space is dry, well-ventilated, and completely weatherized.  The floor is solid and the walls are usually ready to finish with wallboard or paneling.

If codes require enclosed off-street parking, you may be able to add a carport to the side of the garage or house to replace the lost garage.

Each project has unique conditions that may require different procedures, but a typical garage conversion involves the following steps:

1.  Removing the garage door.  Doors vary, but most are heavy and dangerous to remove.  Get professional help unless you are familiar with the mechanism.  If the door is spring-balanced, prop it open with several 2 by 4s.

Find the bolts or hooks that release the tension on the springs, and disconnect them carefully.  Then remove the props, close the door slowly, and disassemble all the hardware and the tracks.  Remove the door from the frame and also any exterior trim around the opening.

convert garage_living space2.  Framing a new wall.  Follow standard framing techniques, except you do not need a double top plate because of the support provided by the header over the door.

Either frame the wall with only one top plate and lift it into place, or fore go a top plate and toenail all the studs into the header.  The soleplate should be pressure-treated lumber or a durable wood species.

Either connect the soleplate to the slab with concrete nails, or drill hole 24 to 30 inches apart for lag shields.  Set the soleplate on a bead of caulk, then bolt the plate to the shields.  As an added precaution, install a termite barrier made of bent metal flashing.

3.  Installing windows and doors.  If the garage will be a bedroom, many building codes require that it have an openable window.  If you frame a door or window in the new wall, the header can be two 2 by 4s because the garage door header actually bears the weight of anything above.

Install the window and door after the sheathing is in place.

4.  Installing sheathing and siding.  Sheathing for the new wall should be the same thickness as the existing sheathing.  Fasten the new panels horizontally with 8d nails spaced 6 inches apart at the edges and 1/16 inch at the ends.

If the new wall is an end wall, the simplest course is usually to remove the remaining panels and install new siding on the entire wall.  If the new wall forms part of the long side of the room, patch new panels into the siding that once surrounded the garage door.

To conceal joints in horizontal boards, cut 2 to 3 feet of board from every other row of siding.  When you install the new siding, the joints will be staggered and therefore less noticeable.

5.  Building the subfloor.  In some cases, you can install finished flooring directly over the concrete slab or install a wood subfloor as you would in a basement.  In most cases, however, the floor of a garage requires insulation because it is at grade level.

You may also want to raise the floor at the same level as that in the rest of the house.  If so, build a subfloor leaving room for insulation.  Allow at least 7 ½ of headroom between the finish floor and ceiling.

Depending on the size of the garage, one or two joist lengths will span the width.  Lay the lengths on shims, sleepers, or girders.  If necessary, place short posts under the girders, use deeper joists, or both.

Toenail the ends of the joists to the existing wall framing.  If wallboard covers the framing, remove the wallboard along the bottom for access.

Install a polyethylene vapor barrier over the garage floor before you install the floor framing.  If the joist spans are longer than 8 feet, install blocking between the joists at mid-span.  Use 5/8-inch tongue-and-groove plywood for the subfloor.

6.  Finishing the walls.  In some garages the studs are exposed.  If so, all you have to do is run wiring and utility lines along them, install insulation and a vapor barrier, and cover with wallboard.

If the walls are already covered with wallboard, probe behind to see if the walls are insulated.  If not, either have a contractor blow in loose-fill insulation or strip off the wallboard and install insulation and new wallboard yourself.

If you use loose-fill, create a vapor barrier by painting the wallboard.  Use two coats of oil-based enamel or one coat of sealer and alkyd.

7.  Installing the ceiling.  If rafters and collar beams frame the roof, they may be the right height from which to hang a finished ceiling.  Collar beams should fall at least every 16 inches, on center.

If your collar beams don’t measure up, and new beams as necessary.  If the roof is framed with rafters and ceiling joists or with trusses (trussed roofs usually appear cluttered with bracing and metal connectors), hang the finished ceiling from the bottoms of the joists.

Again, install additional supports if the joists fall more than 16 inches apart, on center.  The new joists will be long and tend to sag.  Support them at mid-span with strongbacks that attach to the original joists.  After installing the ceiling material add insulation between the joists.

Don’t forget to include a scuttle for access to the attic space you have created.

8.  Finishing the interior.  Tape all the joints and texture the wall and ceiling surfaces.  Install trim and other finishing details, then paint the room.  Install carpet, resilient flooring, or a wood floor over the subfloor.