How to Convert a Covered Deck to a Family Room

Remove any railings around the deck. Take off house siding or leave it, depending on how you plan to finish the interior. Staple a waterproof membrane over the deck floor with a construction stapler and cover it with 1/2-inch pressure-treated plywood for a subfloor; nail plywood to deck flooring at joist locations with 8d galvanized nails and a hammer.

Frame walls with 2-by-4-inch top and bottom plates and studs with centers 16 inches apart. Build rough frames for doors and windows into the walls. Measure with a tape measure from the bottom of the roof frame to the deck floor to determine the height for the walls. Make walls an inch short so they can be assembled on the deck floor using 16d framing nails, then raised into place.

Slide finished walls into place between the subfloor and roof frame. Plumb them with a level and align them with the sides of the deck flooring, making sure corners are square. Secure them with framing nails through the subfloor and decking into the rim joists around the deck and to the roof framing on top. Install prehung windows and doors in rough openings once walls are set.

Seek professional help to install basic heating/cooling and electrical wiring once the rough walls are erected. Sheath the outside of the walls with oriented strand board, nailed to studs and wall plates with 8d nails. Put on full panels and cut out door and window openings with a reciprocal saw. Add rigid foam board insulation over the OSB. Wrap the deck room with a waterproofing house wrap, stapled in place and taped at seams and around window and door openings. .

Install fiberglass batt insulation in wall cavities and between joists in the deck roof ceiling area. Staple batts through flaps on the sides to studs in wall cavities. Buy wider batts if necessary to fit larger spaces between ceiling joists. Cut batts to fit as needed with a utility knife; fill all spaces in walls and ceiling.

Fasten drywall panels to studs inside the room with drywall screws and a screw gun. Do the ceiling first, bracing panels with boards until they are screwed to the joists. Cover the walls with full panels secured to wall plates and studs; use a reciprocal saw or drywall saw to cut out openings. Seal seams and corners with drywall tape and joint compound applied and smoothed with a drywall knife.

Put on exterior siding to match the house. Start siding at the bottom of the deck, at least 6 inches above the ground, and work up to the roof. Finish the exterior with trim at roof edges, corners and door and window openings to match the house trim. Put interior trim around doors and windows to match the rest of the house.

Get professional help for heating/cooling vents and electrical outlets and fixtures, but leave the covers off until the interior walls are painted. Paint the walls and ceiling and the wooden trim. Install carpet, vinyl tile or other flooring and finish with quarter-round or other base trim. Put covers on vents and electrical outlets.