18x20 Pergola Kits

18x20 Refers to the Size of the Pergola's Roof

All of the pergolas featured on this page have an 18' x 20' pergola roof covered by shade purlins, not including the end caps on traditional-style pergolas (which extend 12 inches beyond  the ends of the 18' beams and the 20' rafters, unless you opt for flat end caps). So for all of the 18-foot by 20-foot pergolas on this page, the beams and shade purlins are all 18 feet long (as they run the 18-foot width of the pergola), and the rafters are 20' long (as they run the 20-foot depth of the pergola), not including end caps.

Post Placement for 18x20 Pergolas

The posts (i.e. columns) of a traditional 18' x 20' pergola can be placed anywhere from 0" to 36" in from the outside edges of the beams and rafters (not including the 12" end caps), as shown in this diagram. Most customers choose to place the posts 12 inches in from the ends of the beams/rafters as shown in this CAD drawing, which puts the outside edges of the posts 16 feet apart width-wise and 18 feet apart depth-wise. But again, you can position the posts anywhere from 0 to 36 inches in from the ends of the beams/rafters to create your desired overhangs. It's also worth noting that the overhang can be different on one side than it is on the other sides, if needed or desired.

For modern-style 18x20 pergolas (which never have overhangs), the posts are always in the corners. So for modern pergolas, the outside edges of the posts will be 18 feet apart width-wise and 20 feet apart depth-wise.

All Parts Can Be Trimmed Down to Your Desired Length

To make our pergolas as affordable as possible, we only manufacture the beams, rafters, purlin holders and shade purlins in 2-foot increments (or 4-foot increments above 20 feet). But one or both of the width/depth dimensions of your deck, patio or other outdoor space may be slightly shorter than 18 feet by 20 feet. Using a basic circular saw or miter saw, you can cut any of the pieces down to the exact length required. Thus, the 18x20 pergolas on this page can easily be turned into 17.625-foot by 19.75-foot pergolas (or whatever specific dimensions you need).

Reminder: Width & Depth Are Not Interchangeable

Please be careful when ordering your pergola. An 18x20 pergola is not the same as a 20x18 pergola.

The attached 18x20 pergolas on this page will attach to your home on the 18' side and come 20' out from the wall. For free-standing 18 x 20 pergolas, the shade purlins (which create shade underneath the pergola) must run the 18-foot width of the pergola. So to maximize the pergola's shade, you will want to orient the pergola such that the evening sunlight comes from the 18-foot width side. If your evening sunlight will come from the 20-foot side, you'll want one of these 20x18 pergolas instead.