A deck provides a comfortable place to relax or a spot for outdoor dining. Many decks, however, are open-air, with no roof or covering to protect against rain or sun, which limits their usefulness. Some homeowners opt to install fabric canopies, either permanent or retractable. Others decide to build a roof. The simplest roof for a deck is a shed style, which slopes in only one direction, away from the house. You have two basic options when adding a shed roof over a deck, but check local building regulations before starting any project.
Build a freestanding roof by installing posts or columns at all four corners of the deck; add internal posts if the span is more than 8 feet in any direction. Install 4-by-4-inch or 6-by-6-inch posts depending on the size of the deck. Dig holes at the edges of the deck with a posthole digger and set posts in concrete or fasten them on the deck itself with steel anchors, screwed into the deck, with openings to hold the base of the post. Make the house-side posts higher than those outside to create a roof slope of at least 2 inches per foot.
Frame the outside of the roof with 2-by-6-inch boards attached with framing nails and a hammer horizontally around the four sides of the roof. Nail the side bands into the ends of the outer bands. Fasten those level all away around the roof with a level.
Cut rafters to fit between the back and front bands and install them with metal rafter hangers on the two ends. Use instructions on a framing square and a circular saw to make rafters. Fasten the hangers to the bands with galvanized screws and a screw gun, set 2-by-4-inch rafters in them and screw the rafters in place through holes in the hangers. Install desired roofing over the rafters.
Tying to a House
Tie a deck roof into a house by determining a slope and marking the starting spot on the existing roof or wall. Set posts at the outside of the deck, either in concrete just outside the end of the deck or fastened to the deck in steel post anchors. Set posts lower than the house point.
Remove the shingles or siding on the house, measure the appropriate height from the deck and snap a level chalk line to mark the bottom for a 2-by-6-inch ledger or nailer board to hold one end of roof rafters. Fasten the ledger board to wall studs or roof trusses with lag bolts that screw into the wood. Build a roof frame with 2-by-6 lumber across the outer posts and from the ledger board to the outer band. Nail the frame in place with 16d framing nails and a hammer; put the side bands at the ends of the ledger and outer band.
Make rafters to fit between the ledger and the outer band. Cut them at the appropriate slope and fasten them with metal rafters hangers on the ledger and the outer band. Screw the hangers in place with galvanized screws, set the rafters in the hangers and fasten them with screws. Replace shingles or siding on the house and put any desired roofing on top of the rafters.