How to Build a DIY Pergola for a Deck

Create concrete footings to avoid burying the posts. Wearing safety glasses, a mask and work gloves, mix the concrete in a wheelbarrow and then dig and pour concrete footings centered beneath each post (A). The required depth of the footings will vary by climate and local building codes. Cap each footing with a galvanized-metal post base while the concrete remains workable. After the concrete dries, screw or bolt the bottom of each post to a post base. Then drill and bolt the post to the deck at the rim joist or attach it at the corners with angle brackets.

Cut to length two pairs of 1-1/2-inch-by-7-1/4-inch boards for the long lower supports (B). For each post between the deck sides, cut two 48-inch-long short lower supports (C) and two 17-inch-long cable-bolt holders (D). We used the posts at their full 12-foot lengths, but you can trim these as needed after you assemble the pergola.

Apply two coats of stain to the posts (A), long lower supports (B), short lower supports (C) and cable-bolt holders (D).

Apply adhesive to a cable-bolt holder (D) and clamp it perpendicular to a post at handrail height with the bolt hole exposed. Drive four 3-inch screws through the holder and into the post. Repeat for the holder on the opposite side of the post and for the remaining holders.

Measure and mark the two corner posts (A) at the front of the deck 8 feet from the deck floor. Stretch and snap a chalk line between the marks for the posts in between and repeat as needed along the sides where you’ll attach the lower supports (B, C).

Working with a helper, clamp the first pair of long lower supports (B) to the posts on one end with the bottom edges flush with the chalk marks. Drill pairs of 5/8-inch holes through the supports and post and fasten them together with bolts, nuts and washers. Repeat for the long lower supports on the opposite end.

Stack the short lower supports (C) with the ends flush and drill a 5/8-inch hole through both. Clamp a pair of short lower supports to the post (A) with the bottom edges even with the chalk line. Drill only the top hole through the supports and post. Add the bolt, nut and washer and fasten them snugly — but not too tightly to move — with the supports level. Repeat for the remaining short lower supports.

Fasten the other ends of the cables to the cable-bolt holders (D). Gently pull down the long ends of a pair of lower short supports (C) until they’re level. Drill the second bolt hole through the supports and post. Then add a bolt, nut and washers. Repeat for the other short lower supports and carefully tighten the bolts holding the cables.

Reposition the long upper supports (E) with the notches on the lower supports and the sides clamped against the post (A). Drill a 5/8-inch hole centered on the width of the supports through the upper supports and post and then fasten them with a bolt, nut and washers. Repeat the previous step and this step to install the remaining upper supports.

Where the long upper support (E) connects with a short lower support (C), drill 1/8-inch pilot holes at an angle that allows a 3-inch screw to pass through one support and into the other. Then drive screws on the upper edges of the lower supports and the bottom edges of the upper supports to connect them.

Cut the short upper supports (F) to length and notch them using the same technique as in Step 1. Apply two coats of stain and bolt them to the posts (A).

Cut each slat (G) to length and apply two coats of stain. Where you need slats longer than 8 feet, join two boards with the ends together over a short upper support. Space the slats along the upper supports (E, F) as you prefer with equal overhangs on each end. We used 3-1/2-inch spacing next to the posts and spaced them as evenly as possible in the sections between the posts. Drill 1/8-inch pilot holes through each slat where it crosses an upper support and fasten it using 3-inch deck screws.