How to Build a Pergola Anchored to a Wall

Stretch the tape measure across the wall. Mark the width between the pergola's posts on the ground next to the wall. Set the tape measure's tang against the wall. Align the tang with one of the post marks. Stretch the tape from the wall to the desired position of the outside face of the post.

Mark the location of the post's outside face on the patio slab with a pencil. Move the tang to the remaining mark against the wall, stretch the tape to a similar distance and mark the location of the opposite post's outside face. Stretch a taut chalk line between a corresponding set of marks and snap the string to lay out a chalk line that runs perpendicular from the wall to the outer mark. Create a similar line between the remaining marks.

Stretch the chalk line between the marks that represent the posts' outside faces; in this position the chalk line is parallel to the wall. Snap the string to create a line that runs perpendicularly between the ends of the lines that stretch outward from the wall. Align a builder's square with the perpendicular intersection of two lines.

Check the lines for square, meaning use the 90 degree angle of the builder's square to determine that the lines meet at a 90 degree angle. Check all corners of the layout for square and alter measurements or chalk lines to fix errors. Select brackets according to the size of your pergola's posts. Small pergolas typically require 4-by-4 posts. Pergolas with broad beam spans and large beams require thicker posts, such as 6-by-6 posts. Align post base brackets with the lines that represent the outer and side faces of the posts. Mark the location of the brackets' anchor holes on the slab.

Mount a masonry bit to the drill, set the drill to the hammer setting and bore anchor holes through each anchor hole mark. Align the brackets with the holes and set an anchor through the bracket into each hole. Place a washer and nut onto every anchor. Pound the anchors with a hammer to secure the anchors to the slab. Tighten the anchors' nuts with a wrench to secure the brackets to the slab.

Attach a wood bit to the drill and set the drill to the driver setting. Transcribe the location of the post base brackets' screw or bolt holes onto the bottoms of the posts. Pre-drill screw or bolt holes through the posts and hoist the posts into the brackets. Mount a driver bit or nut driver to the drill. Fasten the posts to the brackets with lag screws and the drill or with bolts and a wrench.

Select post cap brackets according to the size your posts and beams. The top portions of post cap brackets fit the pergola's beams and bottom portions slips over the pergola's posts. Beam size varies according to the weight that the beam must support, such as number and size of joists, and the beam's span. For example, 4-by-4 beams are often suitable for small projects with short spans. Consult a span table, architect or contractor to determine allowable beam span and suitable beam size.

Transcribe the position of the post cap brackets' screw or bolt holes onto the tops of the posts with a pencil. Pre-drill screw or bolt holes with the drill and secure the post cap brackets to the posts with screws or bolts. Transcribe the post cap brackets' upper screw or bolt holes onto the beam and pre-drill holes with the drill. Set the beam into the cap brackets' saddles and secure the beam to the brackets with screws or bolts.

Stretch a line level from the ends of the beam to the wall. Level the line level and mark the beam's vertical on the wall's face. Stretch a chalk line between the marks that represent the beam's position and snap a chalk line between the marks. If your pergola's joists sit atop the beam, this line represents the ledger's bottom edge. If your joists connect to the beam's inner face, the line represents the ledger's top edge.

Run a stud finder along the interior face of the wall and mark the locations of at least two adjacent studs with a pencil. Measure the distance between the studs to determine the wall's stud spacing. Stud finders rarely work through stucco; determine spacing from the building's interior. Return to the exterior wall. Latch a tape measure to the wall's corner. Align the tape measure's height with the ledger's chalk line and stretch the tape across the wall.

The thickness of the wall's siding and sheathing increases the distance from the wall's corner to the first wall stud. Since you are measuring from the wall's corner to mark studs, you must add the thickness of the sheathing and cladding to your spacing measurement. Conventional sheathing is 1/2 inch thick. Common exterior siding, such as stucco, is about 1 inch thick. Wood siding ranges from 1/2 inch to 3/4 thick or more. Add the thickness of sheathing and siding to your spacing measurement. Use the result of this calculation to mark the location of underlying wall studs along the ledger's chalk line.

Select lumber for the ledger. The length of the ledger equals the span of the pergola frame's beam, the ledger's width usually exceeds the width of the joists that it supports and the ledger's thickness is roughly 1 1/2 inches. Cut the ledger to length with a circular saw; the ledger's length equals the length of the beam. Align the ledger with its chalk line and secure it to the wall's studs with lag screws.

Select joist lumber and corresponding joist hanger brackets. Joist size varies according to span and loads. For example, short spans that do not support roof covering materials often require 2-by-4 joists. Consult a span table, architect or contractor to determine allowable joist spans and suitable joist size.

Fasten joist hangers to the ledger with joist hanger nails and a hammer. Typical joist spacing is 16 or 24 inches on center. Mark similar joist spacing on the beam. Cut joists from the framing lumber, set the joists in the hangers and align the loose end of the joists with the marks on the beam. Secure the joists to the hangers with hanger nails and to the beam with framing nails.