How to Build a Wooden Pergola

1. Take two lengths of 150 x 50mm timber, and mark two lines, 2.4M apart, across both.

2. Take two more pieces and mark two lines 2.3M apart.

3. Lay planks together in a rectangle so the inside of each plank rests on the lines of planks beneath it. (The planks can be temporarily tacked at the corners).

4. Position rectangle where you want your pergola.

5. Square the corners by checking that diagonals are the same length (see Fig.1)

6. The inside of each corner of the rectangle, marks the outside corner of each post.

7. Mark post positions on the ground, dismantle and remove rectangle. Dig four holes at least 300mm square at least 900mm deep.

1. Place 100mm concrete in the bottom of each hole and set the posts in place on top. Ensure uncut treated ends go into the hole.

2. Check for plumb levels (vertical) in both directions and brace securely.

3. Pour concrete to 150mm below ground level. Check for plumb again and rebrace if necessary.

4. Leave the concrete to set for at least 24 hours. When the concrete is set, top up hole with soil, then measure 2.3M from ground level on one post.

5. Level that mark around onto each of the others. Level using a string level and string line, or a spirit level on a plank. Check accuracy of all marks by levelling between fourth and first post.

6. Square and cut posts to height(s).

1. Cut four bearers from 150 x 50mm at 2.7M long. Check dimensions at post top before cutting. Shape ends of bearers if desired, remembering that no part of the shaping should extend more than 150mm from end of bearer (see Fig.2), unless you wish to use bearers longer than 2.7M.

2. Temporarily nail bearers to Posts 1 and 4 and Posts 2 and 3. Top edge of bearers should be flush with tops of posts. Sandwich post between bearers (see Fig.3). Bearers should overhang posts by 150mm at each end. Ensure that temporary nails are in the middle of each bearer as bolt holes have to be bored above and below that.

3. Mark points 40mm from the bottom and top edges of the bearers, in the centre of the posts. Bore two 12mm holes through the bearers and posts on those points. If your auger bit is less than 200mm long, measure and bore from both sides, ensuring that you maintain holes level and square to the face of the bearer, so the holes from each side meet up.

4. Grease the bolts liberally, bolt through holes and tighten

1. Cut 9 rafters at 2.7M from the remaining 150 x 50mm.

2. Shape ends if desired, ensuring same limit of 150mm in from ends, unless longer rafters have been selected for use.

3. Nail rafters in place. Start with two end rafters. Line up outside edge of posts with outside of rafters, and have 150mm overhang at each end. Skew nail to all four bearers with 75mm nails. Space evenly at about 300mm centres and nail remaining seven rafters between end joists (see Fig.3 above).

You should ask your council if you need a building consent and/or planning permission, especially if you are attaching your pergola to the house or installing a roof cover