Setting up an outdoor pergola requires a moderate amount of constructions skills plus the ability to use most common carpentry tools. Additionally, painting and concrete skills may be required, depending on exactly what you wish to do with your pergola.
What Type of Pergola?
Pergolas can be built in many shapes, styles and sizes. Some people prefer a small patio pergola, while others prefer a more open garden pergola. Visually, a pergola may be anything from an open-sided, unsheeted roof to an arched trellis. We will build an open pergola, suitable for hanging plants or even clinging vines.
Layout the Pergola
Lay out the corners of the pergola. Each corner post should be set at least 24 inches into the ground, and embedded in concrete. Once poured, concrete should be allowed a minimum curing time of 48 hours. For ease of calculations, set your corners at a multiple of 4 feet. For instance, make the pergola 8 feet wide, and 16 feet long.
The easiest way to install headers, although not the least expensive, is to run 2 x 8 or 2 x 10 along the top of the posts, on each side of the post. This double rail will provide more dependable support for years, even if it becomes weighted with greenery. Be sure to keep your header line straight.
Check the Square of the Pergola
Measure the distance between the inner header at each of the pergola. If this number does not match, adjustments will have to be made. Check the post to make sure they are straight, not leaning inward or outward. Any discrepancies will make it much more difficult to attach the rafters and they will be visably off mark.
Place a cross beam every 8 feet. To build this beam, nail two rafters together. Once the beams are built, notch each end to fit over the header. Rafters should interlock with the headers by at least 4 inches, but no more than half of the height of the rafter. Place the beams, and toenail them into place. Recheck the square of the pergola and make corrections as needed.
All of the rafters will need to be cut in the same manner as the cross beams. In an ideal situation, the rafters will all have matching notches, and can be cut all at the same time. If the pergola is out of square, rafters may have to be measured and cut one at a time.
Install the Rafters
Each rafter should be attached using two 16d nails. Place rafters on 16-, 24-, or 48-inch centers. For best results, cut two blocks of wood to use as spacers, and simply butt each rafter up against the cut piece, nail it in place, and move the cut piece to the other side of the rafter. If the pergola has been built square, the rafters will be evenly spaced on both sides, from end to end.