Finishing off the space above your garage will add living space to your home, and can save the cost of a foundation and roof associated with a traditional addition. The first step is to set a budget and plan what your room will look like. You need to make decisions about several key features.
Check the Ceiling Joists
If your garage was designed with a bonus room above it, you should be all set. But if not, check the ceiling joists or trusses to see if they can support a floor. The building inspector in your town can tell you. If the joists are not up to code, you can attach extra joists to the ones that are there, in a process called sistering.
Do You Need Stairs?
If you can access the space above the garage from another room in the house, you may not need stairs. If the garage is detached or semi-detached, or if you'd the new room to have its own entrance, you'll need to figure out where to put stairs. Check the local building codes, and evaluate whether there is room inside the garage for a set of stairs. If not, you may need to build exterior stairs or enlarge the garage.
Make sure the area above the garage has adequate ventilation before you install insulation. Check for any leaks where water can get in and fix these, too. There are many types of insulation: blown-in, batts, rolls, foam board, spray foam and vapor barriers. Insulation that is sprayed in or blown in is good for hard to reach areas. Batts and rolls come in pre-cut widths, which are good assuming your studs or joists are spaced using standard dimensions. A home center or contractor can help you sort out which type of insulation is best for your situation.
A simple type of floor is to use a plywood sub-floor and install wall-to-wall carpeting on top of it. Floating laminate floor is an easy way to get a hardwood floor look. If heating is also an issue, consider installing a radiant floor heating system. A flooring outlet or home center can help you find the right floor solution for your new room.
Your new room needs at least one window. The easiest way to install a window is to add it into a flat vertical wall. However, a dormer window can add space and height to a room. Think about which direction the sun comes from as well as the cost when deciding which type of window you want.
If you want to add a bathroom, you will add quite a bit of cost to your project. Consider plumbing costs and bathroom fixtures, as well as surfaces like tile, extra doors and lighting, when you are deciding if a bathroom fits in your budget.
If the space is not already heated, you have some choices to make. Investigate the logistics and costs of heating this new room with the same type of heat as the rest of the house. Calculate both installation costs and the costs of heating the new area. Decide whether or not you want to be able to regulate the temperature separately. A separate heating system such as an electric heater might be the answer, depending on the location and type of your existing heating system. Think about air conditioning, too, since rooms above garages can often be warm.
Consider how you'll use the room and decide where you want electrical outlets. You may want a wall switch that turns on an overhead light, or one that turns on power to one of the outlets. An overhead light or fan means more wiring. If you want cable TV, Internet or a phone, have these wires installed before you finish the walls. All of this work can be done by a licensed electrician. Get a detailed estimate from your electrician and be sure his fee covers any necessary inspections and adjustments the inspector may require.
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