How to build a Pergola

How to build a Pergola

Step 1: Choosing a location for your pergola

Ideally your pergola should be connected to a patio, deck, BBQ area, or a courtyard garden. This will extend the living area of your home and enhance those areas. Try to pick an area for your pergola that can make use of the winter sun but block out the summer heat. If you put a pergola in a shaded area you will create a cold zone that no one will want to sit in. If you locate your pergola so it will help block the summer heat then you can create a beautiful area that can be enjoy year round.

Step 2: Marking out and preparing your pergola site

Make sure the area that you plan to build your pergola is clean and ready for use as you will need plenty room to move. Mark out the four corners of the pergola with timber stakes and a builder’s string line. Measure diagonally from corner to corner on both sides to make sure the string lines are completely square. If your pergola is to be attached to a house or close to a house, check the pergola will be square with the house.

Mark out your post holes and dig them out ready to take the posts. You will need to refer to a pergola span tablet to tell you how far apart you need to put your posts.

Step 3: Setting the pergola posts

All pergola posts must anchor into the ground with concrete. However it is best to use a galvanised steel post support that is concreted into the ground and then post is attached above the ground so the pergola post will not rot. Dig your holes 300mm x 300mm wide and 450mm deep. Fill the hole with concrete and then push the galvanised post support into the concrete and into position. Check that the post support is level and in the correct position. Make sure the concrete is not too wet or your post support will sink. It is always best to brace, with timber, your pergola post support while the concrete sets.

Top Tip: While the above set out process is correct, there is a faster and more accurate way is to install your pergola posts after the basic frame of the pergola is in place. This is done by building the pergola on a temporary support frame or prop and when to outer basic pergola frame is in place and is square and correct then dig your holes and cement posts in place. The fastest way is to build the basic pergola frame on props and then measure down to the correct level (30mm above the ground) and cut your pergola posts to suite. Then bolt the galvanised post support to the post and then install on the frame and level the post. Concrete into the post into the correct position. When the concrete has set (next day minimum) just remove the props and your pergola should be strong and completely level and square.

You can build your own prop to build the basic pergola frame on, or hire acro props (adjustable metal posts). Make sure that your props are safe to use and will be able support the weight of the basic pergola frame.

Step 4: Fixing a pergola to the house

There are two main ways to fix your pergola to a house: Attach through the fascia or directly into the wall.

Fascia Attachment

When fixing your pergola to a house with a timber fascia you can use joist hangers and fix directly to the fascia or bolt a beam directly to the fascia. Bolting a beam directly to the fascia is the strongest method. However in higher wind areas it will be necessary to install additional brackets inside the roof, bolting the fascia to the house roof rafters.

If you are attaching your pergola through a metal fascia you must install additional timber and or galvanised brackets behind the fascia inside the house roof cavity. You must also use a beam spanning the length of the pergola and bolt the beam through the metal fascia into the additional support. In short, a metal fascia is not strong enough to support a pergola.

Attach to the house wall

For weather board houses make sure you bolt your wall plate (pergola timber beam that will be attached to the house wall) into the timber studs of the house frame. Attaching your pergola to the weatherboard alone is not strong enough.

How to build a Pergola

For brick houses drill and dyna bolt (expanding masonry bolts) your wall plate directly to the bricks. (However, do not drill into the mortar only drill into the bricks themselves as the mortar is too soft)

Step 5: Adding the Pergola Rafters

Using a pergola span table install the correct sized rafters at 90 degrees to the wall plate and make sure they are square as you go. You will need to fix the rafters to your wall plate and bearers (using galvanised joist hangers) or you can fix them on top of the wall plate and bearer using a framing anchor bracket or skew nailed.

Step 6: Attaching the battens

Battens are used to screw your roof sheets down. They are installed at 90 degrees to the rafters and should be screwed into place. When I build a pergola I nail the battens into place first using a nail gun just to position the battens correctly. Then I screw the battens into place completely with galvanised bulge head screws. If you just nail that battens into place and then add your roofing the whole roof including battens may come off in high wind or storms. If you live on the coast or in a high wind area you must screw your battens down.

Step 7: Finshing your pergola

To finish your pergola all you need to do is check your entire fixings are tight and secure. If you do not want a roof just paint the structure and enjoy it. However many people do want to install a roof which can be ether polycarbonate or metal. The easiest way to finish your pergola off is to paint it first and then install the roof so the paint does not get on the roofing sheets. This method is also the fastest way to finish your pergola and gives the best results.

Tips:

  • 1: High wind support For high wind areas check your pergola span tables as your pergola will require addition support and bracing. All posts will need a 45 degree bracket between the bearer and the post to ‘lock’ the corner. This will stop any swaying motion in high wind.
  • 2: Pergola fixings should be long lasting All of your pergola fixings should be long lasting. For example: bolts, screws, brackets, and nails will need to be galvanised or stainless steel. Coastal areas have the potential of salt spray and thus 316 grade stainless steels fixings are required. This includes all houses within 5km of salt water.


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