Give your deck some extra character and provide a focal point for decoration and design by adding a new pergola. Pergolas are great for vines, other climbing plants and hanging baskets. If you don't have a green thumb, dress the pergola with lights, ribbon or streamers for special occasions. This pergola makes a great weekend project, and a good helper can make the job go much more smoothly.
These instructions are for a basic pergola with square rafter ends. You may alter the design and cut shapes in the rafter ends for a more decorative effect.
- The deck has 2 x 8 joists 16 in. on center (OC).
- The pergola will be 8 ft. square with 4 x 4 posts, doubled 2 x 8 beams, 2 x 6 rafters 24 in. OC and 2 x 6 bracing blocks 24 in. OC.
Check with your local building authorities before beginning to find out if any permits are required. Whether joists are set 12", 16" or 24" OC there will always be joists at multiples of 48"OC.
Laying Out the Site
Follow the steps below to lay out the site for your pergola.Step 1
Determine the approximate area where you want the pergola. Locate a deck joist at one of the corners and mark the decking flush with the inside edge of the joist (mark 1). Measure 8 ft. along the joist and make another mark (mark 2). Snap a chalk line between the two marks flush with the inside edge of the joist.
Partially drive a 6d nail into the decking at mark 1. Tie mason's cord to the nail and pull it perpendicular to the chalk line. Use the following method to square the cord with the chalk line.
3, 4, 5 Method: Measure 3 ft. along the chalk line and mark, measure 4 ft. along the cord and mark it, then adjust the cord until the distance between the two marks is 5 ft. (see Figure A above).
Measure 94 1/2 in. along the mason's cord and make a mark (mark 3). Snap a chalk line between mark 3 and mark 1.
Repeat step 2 from mark 2 to locate mark 4.
Marks 3 and 4 should be flush with the inside edge of a deck joist. Snap a chalk line between marks 3 and 4, flush with the inside edge of the deck joist (see top view of Image B above).
Stand a small piece of 4 x 4 on the decking at mark 1. Align the outside edges of the 4 x 4 with the chalk lines. Trace the other two sides of the 4 x 4 onto the decking. Use a jig saw or a reciprocating saw to cut out the hole for the 4 x 4. (see Image C) Perform the same steps at marks 2, 3 and 4.
Setting the Posts and Beams
The steps below will help you set the posts and beams for your pergola.Step 1
Have a helper slide a 10 ft. 4 x 4 post into the hole at mark 1. Align the bottom of the post flush with the bottom of the deck joist, while the helper holds it plumb. Drill two offset 1/2 in. holes through the post and the joist. (Offsetting the holes helps maintain the strength of your framing members.) Secure the post to the joist with 6 in. x 1/2 in. carriage bolts (see image). Set the posts at marks 2, 3 and 4 the same way.
Measure up 8 ft. 6 in. from the top of the decking on post 1 and mark it. Use a water level to transfer the mark on post 1 to the other posts. Cut each post off at the marks.
Square two 10 ft. 2 x 8s and cut them to 10 ft. exactly. Screw the 10 ft. 2 x 8s together flush. The fasteners should be in rows of three, spaced approximately 24 in. apart and driven in from alternate sides to ensure the boards don't separate.
Measure the distance from the outside of post 1 to the outside of post 3 and subtract that number from 120 in. (The length of the doubled 2 x 8 beam).
Divide the difference from above by 2, to determine the overhang of the beam at each post.
Measure in from each end of the beam and mark for the overhang.
Outside of post 1 to the outside of post 3 = 94 1/2 in.
120 in. - 94 1/2 in. = 25 1/2 in.
25 1/2 in. divided by 2 = 12 3/4 in.
The beam overhang on each side of the posts is 12 3/4 in.
Set the beam with the top of the beam flush with the tops of posts 1 and 3. Also align the overhang marks flush with the outsides of the posts. At each post, drill two 1/2 in. offset holes through the beam and post. Secure the beam to the posts with 7 in. x 1/2 in. carriage bolts (see image above). Set a second beam on posts 2 and 4.
Setting the Rafters
These steps will allow you to set the rafters properly on your pergola.Step 1
Set the rafters 24 in. OC. Find and mark the center of each beam. Measure from the center of the beam and mark it every 24 in. You should have five marks on each beam, one in the center and two on each side. The marks represent the centers of the rafters (see top view of image).
Measure the distance between the beams from outside face to outside face and add 12 in. The extra 12 in. allows the rafters a 6 in. overhang at each beam. Cut five 2 x 6s to length.
The distance from outside face to outside face of the beams is 102 in.
102 in. + 12 in. = 114 in.
The rafters should be cut to 114 in.
Center the rafters on the marks and screw them to the beams. The rafters should overhang each beam by 6 in.
Installing Brace Blocks
Use the following steps to add the brace blocks to your pergola and complete the finishing touches.Step 1
Measure between the rafters and cut brace blocks from 2 x 6 boards (for rafters 24 in. OC the braces should measure approximately 22 1/2 in.).
Number the rafters from left to right (see Image A above).
Measure 10 in. back from the inside face of the beam along rafters 1 and 2 and mark them. Continue measuring and marking the left side rafters 24 in. OC. You should have four sets of marks.
Secure the bracing blocks between the rafters.
Go to the next set of rafters (Rafters 2 and 3) and measure from the inside face of the beam 13 in. and mark each rafter. Then make marks 24 in. OC and install brace blocks. Between rafters 3 and 4 mark and install brace blocks as you did between rafters 1 and 2. Between rafters 4 and 5 mark and install brace blocks as you did between rafters 2 and 3. Offsetting the brace blocks allows you screw through the rafter into the end of the brace block instead of toenailing (see Image B above).
Stain and seal the pergola to match the deck.