The easiest way to build a cover to block the sun and rain over your deck is to construct a pergola. A pergola is an open-beamed roof structure that allows plants or fines to climb on it. By training vines to grow up over the top you create an airy, shady environment on your deck with the added cooling benefit of the greenery supported by the structure. To keep out the rain, simply add clear corrugated fibreglass panelling over the top. This sample is for a 10-foot square structure.
- Skill level:
- Moderately Easy
Things you need
- 4 posts, 4 by 4 by 14 feet
- Posthole diggers
- 8 bags concrete mix
- Shovel, wheelbarrow and water hose
- 1 pound of 16-penny nails and scrap boards
- 5-inch-long, 3/8-inch galvanised lag screws and washers
- Carpenter square
- Drill and 5/16-inch pilot bit
- 8-inch C-clamp
- Socket wrench set
- Circular saw.
- Two pounds 4-inch long galvanised screws
- 12 treated 2-by-8, 10 feet long
- Corrugated clear fibreglass panels (optional - the number will depend on the size of panels you buy)
- Fibreglass panel screws and pilot bit to predrill them
Dig four holes, 2 feet deep. They should be 8 feet apart front to back and 10 feet apart along what will be the front side of the pergola. Make the holes wider at the bottom than they are at the top. Place the posts in the holes. Use the spirit level and nail scrap boards to the sides to prop up each post so it’s perfectly vertical.
Mix the concrete mix in the wheelbarrow with water and a shovel. Don’t make it too wet or the concrete will be weak. Pour two bags of concrete in each hole. Allow curing overnight before continuing.
Attach two 10-foot 2-by-8s flat against the outside edges of the posts. C-clamp the board in place so it stretches from the back to front of the deck. Clamp the boards to the post at an angle that pitches the pergola roof so it’s not less than 8 feet high across the front edge and clears the roof by an inch or so along the back. If the roof has rain gutters, you’ll need this clearance to avoid water running down the rafters of the pergola. The outside boards should hang over each end of the posts at roughly the same distance--a foot or less depending on the pitch of your pergola roof. Pilot drill through the boards into the post and use the socket wrench to screw the joists to the uprights with the lag screws and washers.
Screw a 2-by-8 across the front and back ends of the outside joists so you have a board stretching across the front and back of the square frame. Measure between the front and back boards along the inside and mark them every foot with a carpenter’s square.
Line up each 2-by-8 rafter along the 1-foot marks on the front and back boards. Pilot drill and screw through the end cap boards into the ends of each rafter. Continue attaching the rafters on end, parallel to each other at 1-foot intervals. Remember the pergola is about shade. That’s why the rafters are closer than normal rafter spacing.
Screw clear corrugated fibreglass panels to the top of the rafters if you decide to ward off the rain. Predrill holes through the panels into the rafters and screw them into place. Overlap the edges so they don’t leak. Make sure that any seams that run crosswise are overlapped so the upper panel overlaps the lower.
Start training vines to run up the posts and into the rafters. This will increase the shade. The slatted effect of the rafters turned on edge will cut a great deal of sunlight except at when the sun is straight overhead.
Setting Up a Pergola
Tips and warnings
- To build larger structures, just add the pergola sections in 10-by-10 increments. For better shading, overlap the edges of the deck by 2 to 3 feet to increase sun coverage early or late in the day.
- If using wisteria vines to cover your pergola, beware. You'll have to trim it a lot once it gets big or it will put on very aggressive growth and break apart the pergola framework.
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