What is a Pergola? A pergola is a shade structure which is often referred to as an arbor. It is a structure that can be built as a stand alone garden feature or as an attached structure fixed to the wall or eave of your home.
As a DIY project, a pergola is fairly easy to construct and can be bought as a complete kit from places like www.pergola-patio.com or similar sites that sell kits to the public. You may also opt for buying plans from the internet or from a magazine and do it yourself books like Sunset Magazine and the many Home Improvement books available at the Home Improvement stores like Home Depot and Lowes. Generally, if you can put up a fence, you have most of the skills you’ll need for building a pergola.
Tools: Circular saw, saber saw, shovel or post hole digger, hammer, nails, post concrete, wheel barrow to mix concrete.
Materials: There are kits available in Aluminum, Vinyl and Wood. If you plan to build your own from plans and not use a pre-packaged DIY kit, your choice is probably limited to wood. The advantages of Aluminum kits is that they are very durable, rot and insect resistant and are coated with long lasting baked on enamel finishes. The surface is usually embossed with rich, deep wood grain and it looks very authentic. Another advantage is the weight of materials. Aluminum is very light. Vinyl has many of the same advantages as aluminum. If you choose wood, choose a wood specie that is resistant to rot and insect invasion. Redwood and Cedar are good choices. Pine is not recommended. Wood pergolas will always require more maintenance than either aluminum or vinyl. Wood requires a good quality stain for protection against the elements and will need to be kept well coated with regular maintenance.
Parts: Generally, pergolas have the following main structural parts. Posts, Headers, Beams and Lattice. I will restrict this discussion to wood for now to make this topic easier to digest. The posts are the vertical structural members and almost always are to be set into the ground in concrete. If the plan calls for an 8′ clearance for the headers (a very common number) then the posts will need to be 18" to 24" longer. I always recommend 24" longer for maximum strength as this is the depth of post hole you will need to gain an 8′ overall clearance at the header. Getting your posts set plumb and evenly spaced is critical. The span of your pergola will determine the distance and quantity of posts required. Depending on the look and scale of your pergola, your posts could be 4" x 4" lumber or up to 8" x 8". Use the smaller posts if you plan to cover them with decorative fiberglass columns. I commonly use 4" x 6" posts and use cedar. For a free-standing 14′ x 14′ pergola, 4 posts of 4′ x 6′ is usually recommended. 12′ is the general recommended maximum spacing between posts. On a 14′ x 14′ pergola, the posts are spaced 10′ apart.
Next up is the Headers. Headers are placed directly on top of the posts and are fastened with construction brackets such as Simpson Strongtie. The headers are what determines the width of the pergola (the rafter length is considered the span) and are commonly 18" to 24" longer that the distance of the posts and the quantity required is 2. Headers are usually 3" x 8" lumber. On a 14′ by 14′ pergola the headers are 14′ (since this is a 14′ by 14′ example, the rafters and lattice will also be 14′) and commonly have some type of detail on the end which is traced on using a template and cut with a saber saw. Scalloped, Ogee, Mitered are just some examples of cuts that are commonly made to the ends of headers and rafters.
The next part is the rafters and they are usually 2" x 6" lumber and will have the same decorative cut that the headers have that has been scaled down to fit the narrower lumber. They will extend 18" to 24" beyond the headers and will be attached using construction brackets. I like using 24" on a project this large and larger and like to use the 18" overhang on smaller projects like a 10′ by 10′ or smaller. Rafters are spaced 2′ apart on centers atop the headers. On this 14′ by 14′ example you will have 7 rafters. Put the first one directly in the center and then evenly space and mark out the others locations.
Lattice: Lattice is the very top of a pergola. Generally this is 2" x 2" lumber or 3" x 3" if you can get it. The spacing you use will determine the amount of shade you get from your pergola. From 2" to 4" is a common distance for good shade. 6" to 8" is used when shade is not really an issue. Where I live, I like to use 2" or 3" of spacing in order to get the maximum shade possible. Lattice is nailed straight down into the rafters, no brackets are necessary and the ends can be cut off square or with some beveled detail. Since they are going to be spaced 3" apart in my example, I will need the correct quantity of lattice and to calculate that for a 14′ by 14′ pergola I will convert the 14′ to inches (14 times 12) to get 168 inches and then divide that by 4.5" (because I have decided to place them 3" apart which is 4.5" on center) and I will require 38 lattice boards. Again, start in dead center and work your way to the ends.
So whether you decide to order a complete kit and build it yourself or if you decide to buy plans or design it your self, you see that the construction of a pergola is fairly easy. The strength comes from the posts (cemented in ground) and construction brackets used. The design is ulimited and can be constructed to complement any backyard design. I know you will get many years of enjoyment out of your new backyard pergola!
