Measuring for a pergola is the very first step you need to finish before your construction project begins. First, you’ll need to decide whether you want to build a pergola that is a freestanding unit or an attached unit. If a freestanding unit, you will need four posts. Otherwise, you’ll need a length of board attached to the structure adjoining the pergola.
Draw the Design
When laying out a design for a freestanding pergola, decide if it will be square or rectangular. Once you’ve sketched out the design, it is time to take measurements.
From Post to Post
Measure each side from where the outside of a post would be. This is important, so decide on your post width first to include this in each side measurement. A standard post used in pergola construction is 4x4 inches. Use a chalk line to mark the side measurements where you wish to construct the pergola. Keep in mind that if you wish to slant the roof on a freestanding pergola, two separate sized sets of posts are needed. You will also need to dig post holes to about a foot deep so take this into consideration when designing the pergola.
Your roof and support beams will be 2x6s. Each roof beam should be spaced 12 inches apart, so an eight foot length of roof would require approximately six 8-foot roof beams.
You can purchase pre-assembled lattice wood to place as side walls for your pergola.