How Much Weight Is Safe for a Room Over the Garage?

Assessment

• The joists in the space above many garages are not able to support the weight of an entire room. Unless the house was built with the intention of later adding a room over the garage, it is likely that the garage contains single joists that are not up to local building codes. Because building codes will vary from one community to the next, it is impossible to generalize about how much weight is safe for a room over a garage. Contact your local building inspector to determine local codes as a starting point.

Joists

• In many cases, the transition from an empty space to a living space over the garage is simply a matter of reinforcing the existing joists. The single joist is likely to collapse under the weight of an entire living area with all of its furniture and traffic. Dividing the garage below into two separate parking areas can also provide you with the opportunity to add load-bearing support. In any case, a double joist system will provide you with necessary support for a room addition.

Plumbing

• Another consideration you have to make when creating a room over the garage is whether you will need to add plumbing and additional electrical supplies. Adding an additional bedroom may tempt you to add an additional bathroom to the home also. If you have the space above the garage to add a bedroom and a bathroom, then you may need to add even further reinforcement of the existing floor structure.

Measurements

• Before you begin building an upstairs room over the garage, your best bet it to take one of two actions. First, you can contact a qualified builder or contractor to come in and assess your garage to determine the exact capacity for bearing weight that your garage has. Another is to measure the joist-to-joist distance of your garage ceiling. Create a diagram indicating where you joists are located and then take it to the local lumberyard to talk to a qualified professional. They, too, should be able to give you an idea of your garage's load-bearing capacity.