Specialized brackets, called joist hangers, allow you to connect framing members to a roof's trim board. You can use joist hangers to run joists between one of your existing patio structure's beams and roof. The roof's trim board, called fascia, fastens to the roof rafters' overhang and sits just below the roof covering materials. However, many local building departments prohibit attaching patio structures to the roof and require that you set the patio's joists on the wall's top plate or attach them to a wall-mounted ledger. Check with your local building authority to determine the right construction technique for your project.
Things You'll Need
- Tape measure
- String line
- Framing Square
- Joist hangers
- Joist hanger nails
- Joists, usually 2-by-4 or 2-by-6
- Circular saw
- Framing nails
Use a tape measure and marker to mark the location of one of the outside joists on the fascia. Stretch a string line between the mark on the fascia and the patio beam that will support the opposite end of the joist. Have a partner hold the line taut over the top edge of the beam.
Butt one side of the framing square against the fascia and align the other side with the string. Have your partner move the string until it aligns with the square's edge. When the string and square align, mark the location on the top edge of the beam. This process ensures that the joist runs perpendicular or "square" between the fascia and beam. You will use these initial marks as a frame of reference for the remaining marks on both the fascia and beam.
Align the tape measure with the mark on the fascia and stretch the tape measure across the fascia board. Use the marker to mark the locations of the remaining joists, usually spaced every 16 or 24 inches. Make the marks to one side of the joists' actual installation location; in other words, 3/4 inch beside the center of a 1 1/2-inch-thick joist. If you don't set the marks to the side, you won't be able to see them when you need to use them for installing joist hangers. Lay out a corresponding set of marks on the patio frame's beam.
Draw an X on the side of the marks that represents the center portion of the joist; this will help you remember which side of the mark represents the joists' sides. Lay the framing square over the marks and use the square's edge to lay out straight lines across the beam and fascia at every mark.
Set a joist hanger against the fascia. Align the hanger's inside edge with the first layout line; the X should sit between the hanger's legs. Align the bottom of the hanger with the bottom edge of the fascia. Drive joist hanger nails through each of the hanger's nail holes with a hammer. Fasten joist hangers at the remaining marks.
Measure the distance between the rear of the hangers and the patio beam's outer edge. Add the desired amount of overhang to this dimension. Mark the joists to this length and cut them to size with a circular saw. Hoist one end of the joists into the joist hangers' saddles. Align the opposite ends with the layout lines on the beam.
Fasten the joists to the beam with a hammer and framing nails. A typical nailing pattern for joist-to-beam connection uses three nails, driven at a roughly 30-degree angle through the joist's face. Place two nails evenly spaced on one side of a joist and the remaining nail at the center of the opposite side.
Tips & Warnings
- Always use corrosion-resistant joist hangers and nails for patio framing projects. Acceptable nails include electro-galvanized steel, hot-dipped galvanized steel and stainless steel.
- Acceptable framing methods are subject to local building codes; check with your building department before connecting your patio to your roof's fascia.
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