Building A Pergola

Pergolas are outdoor structures that can be stand alone units or structure attached to the sides of the house that provide semi-protection from the elements. You can even add climbing plants or vines that will provide shade. Before you start building your own pergola, check with the local building authority if you need any building permits, permissions or conditions. Also make sure that your site is clear of any water, gas or electrical lines.

Shop around for a pergola plan that you like, look for inspiration in design or home improvement magazines. Online resources are also a great way to find the design that you want.

The materials below are for a 8 x 10 rectangular pergola.


  • carpenter\’s hammer
  • carpenter\’s square
  • carpenter\’s pencil
  • measuring tape
  • handsaw
  • adjustable spanner
  • builder\’s string line
  • power saw
  • electric drill
  • 12mm (1/2″) drill bit
  • bucket or hose
  • spade
  • wheelbarrow


  • Posts: 100×100 (4×4) – 4 pieces at 3000mm (10ft)
  • Beams: 200×50 (2×8) – 2 pieces at 4200mm (14ft)
  • Rafters: 75×50 (2×3) – 8 pieces at 1800mm (6ft).
  • Bolts: 12mm (1/2″) galvanized carriage bolts 120mm (5″) long – 8 of
  • Nails: 90mm (3 1/2″) galvanized – 1kg (2.5 lb) of
  • Concrete: As needed
  • Batter boards and stakes: 5 meters (16ft) of 50×50 (2×2) – 8 meters (26ft) of 100×25 (1×4) throw-away low grade woodThe wood that you use for this structure must be suitable for exterior use. The posts must be suitable for inground application. Seek advise from your local supplier about the types of wood that would be best for you to use in this project.

Building Your Pergola

Determine where you want your pergola to be, and measure out the space before you head off to buy the materials you need. You need to make sure that the pergola will fit in the space that you’re building it on, too big and it’ll overwhelm your garden, too small and it will look out of place.

Set up a building line

  • Mark out the position by placing a peg in the ground at each corner forming a rectangle 12 ft x 44 inch. These pegs mark the outside corners of the posts. Check to see that they are square by making sure that the diagonal measurement from one corner to the one opposite it is the same as the other two.
  • Cut 12 stakes 2 ft long out of 50×50 stock, then drive them into the ground 2 feet away from the building line. This space will allow you to dig the corner footing holes later.
  • On the corner stake that is on the highest ground, make a level mark one of the 12 stakes 6″ above ground level, then transfer the level mark to all other 11 stakes with a long straight edge and a carpenters level.
  • Nail 100×25 (1×4) batter boards to the stakes, making sure that the top of the batter boards are flush with the level lines marked on the stakes.
  • Run masonry string one batter board to the other, passing directly over the pegs and tie the ends to nails hammered half way in to the tops of the batter boards. This is the approximate building line and perimeter of the pergola.
  • Make sure that the string between AA – BB is the same as CC – DD, and make adjustments if they are not by moving the nail and the string line along the batter board. Do the same for measurements between AA – CC and BB – DD.
  • Make sure the diagonal measurement are square again.

You should now have a level, square building line.

Putting up the side posts

  • Mark the centers of 4 holes for the 4×4 post 2 inches from the building line at the corners.
  • Remove the string line and dig the four post holes, 350mm (14″) square and 600mm (24″) deep. They will need to be deeper if in a frost prone area. See notes in page one.
  • After you’ve dug the holes, replace the string line.
  • Mix 3 parts gravel, 2 parts sand and 1 part cement to make concrete mix. Add clean water to form a consistency that is wet enough to fill the holes by hard enough to hold the posts upright.
  • Position a post vertical into one of the holes and next to (but not touching) the building lines (string lines) where they meet at the corners.
  • Use a plumb level to check that the post is vertical. Have someone shovel concrete around the post to within 2 inch from the top of the hole.
  • Repeat this for all four posts.
  • Leave the concreted posts to cure for about 72 hours
  • Trim the top of one the post to your desired measurement. Higher post gives an elongated look, while shorter post gives an appearance of a wider opening. Measure from the top of the trimmed post to the building line, then transfer that measurement to all other three post and trim them.
  • Measure 8 inches from the top and cut a mark with a power saw to the depth of 2 inch here.  The cut surface is where the outside face of the post is.
  • Repeat on all four posts.

The beams

Cut two 200×50 (2×8) beams 14 ft long. Taper the ends at 30 degrees.

Using the diagram below as a guide, cut a notch 12 inches from the end of a beam that is 2 inch thick and 1 inch in depth. Saw cut them and clean them out with a chisel.

Repeat the same notches on the same beam at 500mm (20″) centers/O.C. There should be a total of 8 notches spread evenly along each beam.

The rafters

Rafter should be 64″ long on the 75×50 (2×3) wood. Also taper the edge with 30 degrees cut.

Repeat the same notching technique that is done on the beams on the rafters, only from the edge at 12 inch distance, 2 inch wide and 1 inch deep. You should have only two notches on each of these rafters (not 8).

Placing the beams and rafters

  • Bolt the beams to the post with galvanized bolts, sitting them on the rebates that you have power-sawed off from the top of the posts.
  • Make sure to align the beam so that each end overhangs the post with the notches flushed with the outsides of the post.
  • Fit the rafters onto the top of the beams, connecting the notches on each sides of the rafters with the notches on the top side of the beams. Tap the rafters gently into place and use 3 1/2″ galvanized nails to secure them onto the beams.