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from Boise, ID
from Boise, ID
18x20 Pergolas
We offer a wide selection of 18x20 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.
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Wall-Mounted 18' x 20' Pergola with Shade Covers - Kit for 4x4 Wood
21% OffOriginal price $1,699Original price Starting at $1,699Original price $1,699Current price $1,349Original price $1,699Starting at$1,699$1,349Current price $1,349Original price $1,699 -
Stand-Alone 18 x 20 Pergola with Canopies - Kit for 4x4 Wood
21% OffOriginal price $1,949Original price Starting at $1,949Original price $1,949Current price $1,549Original price $1,949Starting at$1,949$1,549Current price $1,549Original price $1,949 -
Attached 18 by 20 Pergola and Canopies - Kit for 6x6 Wood
20% OffOriginal price $2,569Original price Starting at $2,569Original price $2,569Current price $2,049Original price $2,569Starting at$2,569$2,049Current price $2,049Original price $2,569 -
18x20 Covered Pergola with Sun Shades - Kit for 6x6 Wood
20% OffOriginal price $3,299Original price Starting at $3,299Original price $3,299Current price $2,639Original price $3,299Starting at$3,299$2,639Current price $2,639Original price $3,299
18x20 Refers to the Combined Inner Dimensions of the 4 Roof Openings
When we say a pergola's dimensions are 18x20, 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 18' wide and a total of 20' deep.
The overall outside-edge to outside-edge dimensions of the pergola will be:
- 19' 2.6" wide x 21' 2.6" deep (if you choose a kit for 4x4 posts) OR
- 19' 10.6" wide x 21' 10.6" deep (if you choose a kit for 6x6 posts)
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 18' x 20', you would need to:
- Purchase three sets of two posts totaling 18 feet to be the beams running the 18-foot width, and then cut off a total of 14.6 inches (for 4x4 wood posts) or 22.6 inches (for 6x6 wood posts) per set of two posts; and
- Purchase three sets of two posts totaling 20 feet to be the beams running the 20-foot depth, and then cut off a total of 14.6 inches (for 4x4 wood posts) or 22.6 inches (for 6x6 wood posts) per set of two posts
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.
Reminder: Width & Depth Are Not Always Interchangeable
18' x 20' pergolas are different from 20' x 18' pergolas. The wall-mounted pergolas on this page will attach to your home on the 18' width side and come 20' out from the house wall. For free-standing pergolas with a slatted roof, the roof rafters will be mounted to the 20' beams and run the 18-foot width of the pergola (providing more shade when the afternoon/evening sunlight comes from the 18-foot width side). If your afternoon/evening sunlight will come from the 20-foot side, you'll want a 20x18 pergola instead.