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We offer a wide selection of 20x18 pergola kits, including both free-standing and house-attached kits, those with shade canopies and those made for a slatted wood roof, and some made for smaller 4x4 wood frames and others for larger 6x6s. Use the filtering options below to quickly find the perfect 4-block pergola kit for your outdoor space.
When we say a pergola's dimensions are 20x18, we are referring to the combined inside dimensions of the 4 roof openings (from inside-edge to inside-edge). All of the kits featured on this page are meant to have 4 roof openings, arranged in a 2x2 grid, which combine to be a total of 20' wide and a total of 18' deep.
The overall outside-edge to outside-edge dimensions of the pergola will be:
With all of this being said, you can easily change the overall size of your pergola by trimming the wood posts that you plan to use for the roof beams. For example, if you wanted the true outside-edge to outside-edge dimensions of a free-standing pergola to be exactly 20' x 18', you would need to:
Important Note: Our shade canopies are specifically designed to fit roof openings that are exactly 8x8, 8x10, 8x12, 10x10, 10x12 and 12x12. If you're purchasing a kit with shade canopies, you cannot trim down the roof beam posts. Furthermore, all roof posts must be 8-, 10- or 12-foot lengths.
20' x 18' pergolas are different from 18' x 20' pergolas. The wall-mounted pergolas on this page will attach to your home on the 20' width side and come 18' out from the house wall. For free-standing pergolas with a slatted roof, the roof rafters will be mounted to the 18' beams and run the 20-foot width of the pergola (providing more shade when the afternoon/evening sunlight comes from the 20-foot width side). If your afternoon/evening sunlight will come from the 18-foot side, you'll want an 18x20 pergola instead.