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Building a Pergola
Two of the biggest questions people ask about building a pergola are "how to dig post holes" and "how to attach beams to posts" - (here is our article on Digging Pergola Footings)- this article will concentrate on your beam to post attachment options.
Just one final word on post holes before we begin - you can make sure that you are digging deep enough by visiting your local building office to check the depth of the frost level in your area - the idea is that if you start cemetation for your posts below the frost level - your structure is less likely to move as the ground freezes and then thaws.
Also - make sure that your order posts long enough to take into account what has to go into the ground - leaving you with a comfortable structural height that you can still move around under even when it is weighed down with vines or climbing plants like honeysuckle overhead.
One of the most important decisions apart from style, lies with how you want your pergola construction to be made - this will have an everlasting effect on the final look of the structure.
The big question is to notch or not to notch.
Undoubtedly it takes more time and effort to correctly measure and notch your posts so that the beams fit snugly into the top of the pole, it takes even more time to notch rafters so that they smoothly fit over the beams but the overall finish is much more professional without metal fasteners showing.
this graphic showing three different examples of attaching the beam to the exterior face of the post helps explain the differences in more detail...
Wood pergola constructions made from quality pressure treated timber deserve careful measurement and notching.
A square garden pergola will only have four corner posts to notch, while a larger wide rectangular garden pergola that needs to accomodate all of your extended family eating out - might have six posts.
On the other hand - a pergola arbor is usually a thinner, longer structure that is made to walk through and when they are established with wonderful climbing roses, clematis, jasmine or honeysuckle - they provide a wonderful journey from one part of your garden to another.
The notch is cut out at the top outer side of the post - to the size of the beam - once this is done on the outer face of both posts of one side - the beam can rest comfortably in place spanning both posts - while you fix the carriage bolts or lag screws through the two pieces of wood - and with washers and nuts tightened on the inner side.
(fixing the beam to an unnotched post is not so easy - you need more hand to help you keep the beam in place while you attatch it)
When you pre-drill and then counterbore the pilot holes through the beam and continue level through the post to the other side - it's quick and easy to get your bolts in with the head of the bolt on one side and the nut on the other - actually deeper than the surface of the post - these fasteners can later be covered over with small round wood plugs... and the fasteners disappear all together.
If you find it difficult to image the finished look from the perpective of the above two graphics - this is how your two main options for attaching a beam when building a pergola will look like.
If you want to measure and cut the timber to size yourself - It's important to buy a quality pergola plan that has accurate measurements and comes with all the instructions you will need to get started on creating your wonderful outdoor room like this one here...
Not long ago it was easy when there was just the one basic model available, but with such a recent surge of interest in pergola construction, there are now many different types and materials to choose from.
Larger homes and gardens can take bigger impressive posts and chunky beams to form the traditional country pergola, more modern surroundings often look better with 6 x 6 posts, 5 x 5 posts or perhaps the 'lighter look' of 4 x 4 posts.
We are now just starting to create more interesting mixes of materials, for example by using aluminium posts with wooden beams, rafters and purlins - and instead of the typical square posts, columns are coming more into favour and are being used when building a pergola which will be totally white or by using white columns with all natural wood uppers.
You will want your structure to look good, but if it is going to have any chance of becoming a real asset to the value of your home you want to also concentrate on quality - not only quality timber, but also quality pergola construction - it's worth taking your time to plan well to create a wood pergola with the best building methods and hardware available.
Investing your time and money in Building a Pergola should result in a solid structure that will withstand the winter winds, resist moisture as well as repel insects. Build well, continue to protect your timber over time and this is one garden structure that could still provide enjoyment for your family in 50 years time.
Last Modified: January, 2007
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