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20x18 Pergolas

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.

  SIMILAR SIZES:  18x18 pergolas  |  18x20 pergolas  |  20x20 pergolas  |  22x18 pergolas
  • Attached 20x18 Pergola Off House with Roof (6 Options) - Kit for 4x4 Wood

    Original price Starting at $999
    Original price Starting at $999
    Original price $999
    Starting at $799
    Starting at $999 $799
    Current price $799
    Original price $999
    20% Off

  • Freestanding 20x18 Pergola Kit with Roof (6 Options) - For 4x4 Wood

    Original price Starting at $1,249
    Original price Starting at $1,249
    Original price $1,249
    Starting at $999
    Starting at $1,249 $999
    Current price $999
    Original price $1,249
    20% Off

  • Wall-Mounted 20' x 18' Pergola with Shade Covers - Kit for 4x4 Wood

    Original price $1,699
    Original price Starting at $1,699
    Original price $1,699
    Current price $1,349
    Original price $1,699
    Starting at $1,699 $1,349
    Current price $1,349
    Original price $1,699
    21% Off

  • 20' x 18' Pergola Attached to House with Roof (6 Options) - Kit for 6x6 Wood

    Original price Starting at $1,879
    Original price Starting at $1,879
    Original price $1,879
    Starting at $1,499
    Starting at $1,879 $1,499
    Current price $1,499
    Original price $1,879
    20% Off

  • Stand-Alone 20 x 18 Pergola with Canopies - Kit for 4x4 Wood

    Original price $1,949
    Original price Starting at $1,949
    Original price $1,949
    Current price $1,549
    Original price $1,949
    Starting at $1,949 $1,549
    Current price $1,549
    Original price $1,949
    21% Off

  • Free-Standing 20' x 18' Pergola with Roof (6 Options) - Kit for 6x6 Wood

    Original price Starting at $2,499
    Original price Starting at $2,499
    Original price $2,499
    Starting at $1,999
    Starting at $2,499 $1,999
    Current price $1,999
    Original price $2,499
    20% Off

  • Attached 20 by 18 Pergola and Canopies - Kit for 6x6 Wood

    Original price $2,569
    Original price Starting at $2,569
    Original price $2,569
    Current price $2,049
    Original price $2,569
    Starting at $2,569 $2,049
    Current price $2,049
    Original price $2,569
    20% Off

  • 20x18 Covered Pergola with Sun Shades - Kit for 6x6 Wood

    Original price $3,299
    Original price Starting at $3,299
    Original price $3,299
    Current price $2,639
    Original price $3,299
    Starting at $3,299 $2,639
    Current price $2,639
    Original price $3,299
    20% Off

20x18 Refers to the Combined Inner Dimensions of the 4 Roof Openings

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:

  • Purchase three sets of two posts totaling 20 feet to be the beams running the 20-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 18 feet to be the beams running the 18-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

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.