The Great Garage Conversion

By Paul Bianchina

If you're searching for a way to accommodate a growing family or achieve a spacious home office without undertaking an addition, one solution might be to convert your garage to living space. The following sections cover some of the most commonly encountered questions, and how to deal with them.

What About the Cold Floors?

Since the garage has an uninsulated concrete slab floor, attention needs to be paid to how to make the floor warmer and also more resilient. You can accomplish both those tasks by furring the floor up using lumber and plywood. Remember that any lumber in contact with the concrete either needs to be pressure-treated or be protected by placing a layer of 15-pound felt paper between the wood and the concrete.

First, determine how much you want to raise the floor. At a minimum, you'll want to utilize a 2x6 joist to provide enough cavity for R-21 insulation. Deeper joists provide for more insulation, and if your garage was built at a lower level than the house, you may want to use a joist that's deep enough to raise the garage floor up level with the floor of the house.

To allow for water runoff, almost all garage floors have some amount of slope from the back wall down to the wall with the garage door in it. To achieve a level floor, you'll have to adjust the joists accordingly. If you are running the joists side to side - perpendicular to the slope in the floor - each of the joists will either have to be ripped down or shimmed up (or a combination of both) to make the floor level. If the joists are parallel to the slope, you can rip them on a taper or use shims to get them level.

After the joists are in, you can run any underfloor plumbing you need, as well as any ducts or electrical wiring. Finally, insulate the cavities and then install sheets of tongue and groove plywood subfloor, using adhesive along with your fasteners.

How Do I Line Up the Walls with the Foundation?

Typically, framers don't expend a lot of energy in getting garage walls even with the foundation they sit on. The result is walls that may be set back from the foundation wall in some areas, and perhaps overhang it in others. You may also have 2x4 wall construction that doesn't allow for as much insulation as you'd like.

Again, one step - in this case, furring - will solve both problems. Select a lumber size that is deep enough to extend the wall framing past the concrete - usually anywhere from a 2x2 to a 2x4. Notch the end of each furring strip so that it will fit over the concrete foundation wall, and attach one strip to the face of each wall stud. The result will be a wall that is even and that completely hides the foundation, as well as being deep enough for R-21 wall insulation, which meets today's building code requirements for most areas. 

How Do I Deal with All Those Obstructions?

Garages often have exposed obstructions, such as ducts, pipes, wires, odd jogs and other impediments to smooth walls. If the obstructions are small enough, such as wires or small-diameter pipes, you may be able to adjust your furring strips enough to accommodate them. Just use deeper furring on the wall that has the obstructions.

For larger obstructions, the easiest solution is to box around them. Construct a box from 2-by lumber that surrounds the obstruction, then drywall over it when you finish off the walls. If the obstruction in question is something that you'll need access to - a water heater for example - you can frame it in and enclose it on three sides, and then provide a door or a removable access panel on the fourth side.

What About the Garage Door?

Typically, the best appearance both inside and out is achieved by removing the door entirely. Once removed, avoid the temptation to just frame in the opening all the way down to the ground - this is a dead giveaway from the outside that the room used to be a garage, and diminishes both the look and the resale value of the conversion. Instead, form and pour a concrete foundation wall across the opening that's the same height as the adjacent foundation walls, then frame up on the that. If you're careful about matching your siding and trim - remember to stagger back siding joints to blend them in - the converted garage will be virtually indistinguishable from the rest of the house.

Remember that all garages are different, and your methods and materials will need to be adjusted accordingly. Also, a building permit is required for a garage conversion in just about every jurisdiction.

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