Building A Pergola In Your Garden – You can add a pergola to an existing deck or patio, or plan it as part of a new outdoor living area. It is important to provide adequate footings for the posts but the framing need not be as strong as for a deck, as pergola roofing materials are usually light in weight. Of course, the framing must be sturdy enough to withstand strong winds and resist collapsing under the weight of climbing plants and, occasionally, snow.
A pergola can be built from treated pine or a hardwood such as oak. When deciding on a timber, consider costs as well as the aesthetic effect you want to achieve. Consider the style of the posts, beams and rafters you require — and whether a particular surface finish is needed to match the house. As well as timber, you need concrete, post brackets and fixings to secure the beams and rafters, if used.
In choosing a roofing material, first assess how much shade you’ll need. A pergola on the south or west side of the house may require full protection from the sun, while one on the north may be better left open to the weather. You may also choose to use a material that will shelter you from the rain. Remember, however, not to use anything that will prevent light or ventilation from reaching indoors.
Although building your own pergola will allow you to tailor the design to meet your requirements exactly, many garden centers and large DIY stores sell pergola kits, which come with all the necessary posts, beams, brackets and fixings. These are modular in design, allowing two or more to be joined together to form quite complex structures, either attached to the house or freestanding.
Attaching a pergola to the house
A pergola is attached to the house by means of a wall plate. To attach a wall plate to a brick or stone wall, use 100 mm expansion bolts, drilling their holes with a masonry bit and electric SDS drill. If your house is weatherboarded, attach the wall plate to the wall studs (through the board), using 75 mm galvanized coach screws, having first drilled pilot holes. The height of the wall plate will determine the height of the pergola. You can make it any height, but to ensure adequate headroom, make it a similar height to the ceilings inside your house. Make sure the wall plate is level along its length.
Most pergolas have plain posts that suit the relaxed garden atmosphere, but there are many ways to dress them up. For a more formal setting, choose columns to reflect that, or be innovative and make your pergola posts a design feature. If you want ‘columns’ rather than mere posts, make them from three 150 x 50 mm lengths of timber. Cut down the length of two of them, removing 50 mm from each of the outer corners. Fix the cut timbers to each side of the uncut one to form an octagonal column. Shape the ends of the beams with a jigsaw. Pergola posts can be structures in their own right. Construct a post with four verticals (75 x 75 mm) joined by horizontal battens (75 x 38 mm at top and bottom with 75 x 25 mm battens in between) at 500-mm centers to form trellis-like posts that can support climbing plants.
Fixing the posts
When adding a pergola to a timber deck, locate the posts above the deck supports. Use posts about 100 mm longer than the plan calls for, then trim their tops. Secure the new posts with angle brackets or post brackets. Posts should not rest on a concrete patio that has no footings underneath, as the concrete could crack. If building a new patio, pour a concrete looting along with the patio and embed post brackets in it. If you are adding a pergola to an existing patio, position the posts just outside the paving to avoid having to break into the concrete. Dig post holes about 230 mm wide and 300 mm deep in the required places, put gravel in for drainage and set the posts in concrete.
Erecting the pergola
The basis for most pergolas is the 100 x 100 mm post set firmly into the ground. Place the posts so that they do not block access to doorways or an attractive outlook. To improve the appearance of your pergola, construct beams by placing a strip of plywood between two 300 x 50 mm lengths of timber to create a section that was the same thickness as the 100 mm post. If you struggle with cutting plywood sheets, Cut My Plastic can do that for you.The plywood was nailed to one length of timber first and then the beam nailed together from both sides. For a lighter pergola, use a single 150 x 50 mm beam. For rafters, choose 150 x 50 mm timber. Battens can be of 50 x 50 mm or 38 x 38 mm timber.