A pergola can be a beautiful addition to your outdoor spaces. It helps to define a space as a patio, porch or garden accessory. When under a pergola, the goal is to help minimize some exposure to the elements while not eliminating them. If you are building your own pergola, the roof may seem like a mysterious matrix of beams and rafters. Relax, it is much more simple than you think.
The roof of a pergola is designed with strong support rafters, held up by anchored posts in the ground. These rafters hold smaller beams that cross the structure's rafters. Most pergola roofs are square or rectangular as this keep the lines clean and is a nice way to define the structure. There are two ways to place the beams on the rafters: bolting or notching.
Bolting is the simplest way to attach the beams to the rafters. Measure out how much space you want between the beams that will go over the rafters and how wide the beams will be. This will determine how many beams you need. The size of the beams plus how far apart they are set will determine how much light is able to penetrate the roof. Six inches is usually a reasonable distance between beams.
To secure the beams, center them on the rafters such that each end is overhanging equally on each side. Use three-inch screws or nails to secure each bolt along the rafters. You may want to use hurricane ties to further secure the beams if you are in a location where extreme high winds may require stronger fasteners.
A notch inlay takes more time and effort to do right. This type of roof doesn't lay the beams on the rafters and bolt them in, it measures and cuts notches into the rafters where the beams will rest. Like putting a puzzle together, you will want to properly measure everything prior to starting and lay out the beams to make sure you have the design you want. This method, when done right, doesn't need fasteners or bolts to hold the beams in place. They should be securely held in the notches while remaining flush to them. While you don't need fasteners, you may want hurricane ties discreetly installed to prevent damage in high wind situations.