A pergola can provide shade, increase privacy and add a pleasing sense of enclosure for an outdoor space. When installed over a window, it can extend those same qualities to the neighboring indoor space. In most cases, placing a pergola over a window involves attaching one side of the structure to the house wall, by means of a ledger board, while the other side is supported by two or more posts. Because the structure is attached to the house, the posts must be anchored to concrete footings that extend below the frost line, the depth to which the ground freezes in winter.
Things You'll Need
- Excavation tools
- Concrete and tube forms
- Post bases
- 4-by-4, 4-by-6 or 6-by-6 posts and beam
- 2-by-6 or larger lumber (ledger)
- 2-by-4 or larger lumber (rafters)
- 2-by-2 or other lumber (optional roof slats)
- Lag screws
- Washers and/or Z-flashing
- Post-beam connectors
- Joist hangers and nails
- Framing nails
- 3 1/2-inch deck screws
Mark the locations of the posts and ledger board, making sure the layout is square (each corner is exactly 90 degrees). Mark the centers of the post holes onto the ground, using stakes. Mark a reference line for the ledger onto the house wall, using a level.
Dig the post holes according to the local building code. Pour the concrete piers, using a cardboard tube form, if desired. Set an anchor bolt into the wet concrete of each pier. After the concrete dries, install the posts with metal post bases. Support the posts temporarily with cross-bracing.
Cut the ledger board to length and position it on the house wall. Drill pairs of pilot holes through the ledger and siding at each wall stud location. Fasten the ledger to the wall with pairs of lag screws at each stud, using washers behind the ledger to create an air gap between the ledger and the siding. With some types of siding, you may have to cut out the siding and lay the ledger over the wall sheathing (and building wrap); install Z-flashing above the ledger to keep water away from the wall.
Cut the beam (or beam members) so it overhangs the posts, as desired. Install the beam over the tops of the posts with post-beam connectors.
Lay out the rafter locations on the top edges of the beam and ledger, using the desired spacing for the rafters. Transfer the marks to the ledger face with a framing square. Fasten a joist hanger to the ledger at each location, following the hanger manufacturer’s directions. Cut the install the rafters with their house ends fastened to the hangers and their outside ends fastened to the top of the beam; the rafters should overhang the beam, as desired.
Cut and install roof slats, if desired, over the tops of the rafters. These can simply be 2-by-2s running perpendicular to the rafters, or you can use 1x boards set at an angle to create a louver that blocks midday sunlight in the summer but allows the sun to penetrate during the winter, when the sun is lower in the sky. If necessary, add knee bracing to provide lateral support between the posts and beam.
Tips & Warnings
- Contact your city’s building department to learn about zoning, permitting and building code requirements pertaining to your project.
- “Start-to-Finish Patios;” Meredith Books; 2004
- “The Complete Outdoor Builder;” Creative Publishing international; 2006
- Photo Credit Comstock Images/Comstock/Getty Images
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