Rafters spread roofing loads across beams, making it possible to use roofing materials too insubstantial to span the distances between beams.
Rafters must support their own weight over open space without sagging or twisting and also support the weight of the roof covering. For a roof that must shed water, they are sloped. Rafters may connect to ledgers and beams any of several ways. The right method to use depends on the roof's design.Decoratively cutting rafter ends can give a patio roof or gazebo a distinctive style. If you wish to add decorative detailing to rafters, do so before you lift and fasten them into place. Use a saber saw for making curved cuts.
Attaching rafters to a ledger. With a house-attached overhead, rafters are fastened to the house at one end. Metal framing connectors make the best connections.
Joist hangers can hang rafters from a ledger, but, for sloping rafters, notch them or use special rafter hangers. If rafters will sit on top of a ledger, attach them with seismic anchors as you would attach rafters to a beam.
Splicing rafters. Where rafter connections will not be visible, rafters can be spliced together end-to-end with board lumber “gusset plates.“
To do this, butt the ends of the rafters together over a supporting beam. Then nail two pieces of 1-by or 2-by lumber of the same width as the rafters (see left) and about 18 inches long centered over both sides of the splice. Or, join the members using manufactured metal splice plates.
Be sure each rafter end sits a full inch on the supporting beam. If you must splice several rafters, stagger the splices over different beams to prevent a weak substructure.
Another splicing method—though it does not utilize uniform spacing—is to overlap the rafter ends that are supported by beams. If more than one splice is needed on a full rafter length, alternate overlapped sides.
For standard 2-inch lumber, nail both faces of each splice with six 8d or 10d common galvanized nails. This type of splicing, as shown above right, adds lateral stability to the rafters and may eliminate the need for bracing.Sloping rafters. Fitting sloped rafters in place can be tricky for a novice. It’s usually easiest to cut one rafter to fit and then use it as a template for the rest, but this only works if the supporting beam and ledger (or second beam) are perfectly parallel.
To cut sloping rafters for a house-attached patio roof, lay a rafter board so it rests on its edge on both the ledger and the beam parallel to the ledger. Then force the rafter’s tip snugly against the house wall. Using a block of wood as a ruler, mark the ends for cutting.
Cut the triangular piece off the rafter end that rests on the ledger and off the end that rests on the beam, as shown below. Cut bird’s-mouth notches where the rafter rests on the ledger and on the beam.
Place the rafter in several positions along the ledger and the beam to check for fit. Then mark and cut the remaining rafters, using this rafter as a template. Before fastening the rafters in place, treat them with a wood finish.
Patio Roofs & Gazebos
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