If you grew up in the '70s, you probably had at least one friend who lived in a house that had a garage that had been converted into a room. Burgeoning postwar families frequently outgrew their available space faster than their paychecks could afford new digs, so the garage conversion became a common way to add on an extra bedroom, living room or just elbow room.

Most of these rooms, however, were unmistakably garages with a thin veneer of civilization wrapped around them. Frequently, not much attention was paid to making what had not been a homogenous part of the interior world seem to be one. Concrete floors were left uninsulated, walls were covered in the sort of ghastly faux-wood paneling that became emblematic of the period, and often garage doors were even left intact.

With today's real estate market prices in many areas fast outstripping the earning power of young families, the garage conversion is again becoming popular. Now, however, much more attention is being paid to making the former "car barn" into a smoothly blended part of the home's original interior.

According to Steve Donnelly, of Donnelly Custom Construction, there are several subtle changes that must be made to make your garage into a spare bedroom that won't feel like an afterthought.

Where To Start

The trick, he said, is to start from the ground up. That means that lovely concrete floor is going to require some work. A layer of plywood or lumber will provide insulation and prevent the floor from freezing feet in winter. Check your local building codes to confirm any local requirements before you buy your materials. The same applies for any other steps you take.

You might think the walls are a simple matter of putting Sheetrock or plywood over the exposed beams after putting up some insulation. However, many garages are framed with 2 x 4s, while the living spaces are frames with 2 x 6s. That's two extra inches of insulation space. A "furring strip," a flat piece of lumber used to build up or level a wood surface, can buy you the extra inches you need.

The strips can also cover up imperfections. Frequently, garages are where lumber that gets dinged or dented elsewhere on the jobsite ends up. If you have an otherwise-solid board that has a slight warp or bend, furring strips can help even things out.

Ceilings in most garages are finished, but may not be aesthetically pleasing. It may be a simple as a coat of paint, or you may need to try your hand at texturing or "stomping" the surface to fit in with other parts of the house.

Planning The Exterior Appearance

The garage door opening is likely going to be the most involved part of the actual construction, and unless you are a highly skilled do-it-yourselfer it's the one part best left to a professional. Donnelly likes to take a picture of the front of the house and try to style the exterior of the garage to match. One mistake he said many conversion plans make is to simply make the front of the garage blank siding or brick. If no other part of the house has such a large expanse of blank wall, it will stick out like a sore thumb.

Putting a window or exterior door in the garage door fill-in also helps prevent the "cave" feeling that frequently makes converted garages such claustrophobic spaces.

Speaking of claustrophobia, you'll want proper electrical connections in your new room so that things like lights can be plugged in. If you want to turn it into a home theater room, you'll need beefier wiring. Whatever your plans, Donnelly said, at the very least have the work thoroughly inspected by a licensed electrician before you plug in the big screen or install your ceiling fan.

In short, it's easy to make a garage into an extra room, but far more involved to make it look like it's not an afterthought. Donnelly said it's fine to do the work yourself, but get advice from professionals in the design, planning, and construction phases and be sure to follow your local building codes. Many states have owner-builder networks that can put you in touch with advisors licensed in all specialties.