When I was a teenager in the seventies, family friends of ours bought a new house. I remember the mother showing us the her new home. She proudly displayed her youngest and then her oldest daughters’ rooms. We moved on to her bedroom. I turned to my friend Utz,her son, and asked him where his room was. He took me to the garage, and showed me a cot by the car. He turned to me and said in a deadpan voice,”they are thinking of putting up a wall.”
Today garages are converted into offices, work areas, family rooms, or bedrooms. This space has been appropriated for other rooms too. I would say that about a fourth of the homes that I inspect have had some amount of remodeling done to the garage. Builders are encouraged to consider that a garage may be converted, so they should take steps to make that conversion easy to accomplish.
Still garages are meant for cars and storage, and builders must take that into consideration when designing and building a garage. Since most conversions are done to attached garages, I will focus on them. Garage floors are built lower than the floors of your home, because chemical spills or fumes that stay low need to be prevented from entering your home. An attached garage should be isolated from the rest of the house by material that would prevent a fire from sweeping to quickly into the living quarters. Garages should have GFCI outlets since water and electrical cords can come in contact here. Water heaters should have their burner compartment eighteen inches off of the floor, and the unit itself should be protected from a car driving into it. The walls and the ceiling will not need insulation, since the area is not meant for habitation.
Your first steps in a remodel of the garage would be to plan out the wiring and plumbing. You will want this done before sheetrocking the walls. About the wiring, extension cords are not acceptable for wiring. They seem to be used in garages quite a bit. The next step is insulating the room. If your garage already has sheetrock on the walls, there is a good chance that no insulation was placed behind them. You can blow loose fill insulation behind them, or you can redo the sheetrock. If you are doing new wiring or plumbing, you may have already removed the old sheetrock. Remember to insulate in the attic above the garage. If you are leaving the garage doors in place for now, you may want to use a rigid foam board insulation in the spaces. Then you can look to see how foam insulation could be used around the doors to stop the draughts. When installing sheetrock, use screws. Builders always use nails to install this product, but it is not the proper fastener. Screws will hold the boards against the studs better.
If the garage will be used for cars or storing chemicals, I would not raise the floor or run duct work from your existing air conditioning system. You will still want to isolate this room. For your air conditioning needs, use a window unit. You could cut a hole in the wall, and then frame a window for it, or place this unit in an exterior door. If you are not raising the floor, you could use any floor treatment that you want, but remember that water may come in under the garage door. A simple floor treatment would be floor paint and a seal coat. Raising the floor by building a wood frame is common. This type of floor feels nice under foot, but if you have built a wall where the garage doors had been, you have created a problem. Moisture will become trapped under this floor, and this situation can cause damage to the boards used for the floor framing. A more expensive route (but better in the long run) is having a new floor poured. However; if you do install a wall where the door is, you do not have to raise the floor.
Unless you are going with a full remodel, you should think about how a new owner may want to use the space. If the changes do not prevent the garage from being used as a garage, you will have no qualms from future owners. One conversion that I saw had the garage door sealed shut, but it was still a door. To undo this change was going to take a lot of effort on the new owners part, because of the way it was accomplished. The new owner liked the change, so he did not want to undo it.
I hope that I have given you enough to ponder when contemplating changing the function of this space. I look down my street, and I think that half of us do not use our garages for cars, so we may consider developing this square footage to a higher purpose.