Hey everyone! I'm looking to build a pergola with wooden rafters over my oddly sized backyard deck, which would require approximately a 12x20 pergola. The tricky part is that I want to avoid having a center support beam as it would block a door on one side and obstruct views on the other. We're located in Northern California, where we face heavy rain and some strong winds, but no snow or tornadoes.
I haven't had much luck finding pergola kits that can accommodate our size without a center beam, so I'm thinking of constructing one myself. There's a local company called Wild Hog Linx offering prefab hardware that I might be able to incorporate into my project. Do you think my plans will be structurally sound without sagging? I'm aware that I'll need additional components and will have a handyman to assist with the assembly.
3 Answers
You might want to consult with an engineer on this. The load of the materials, the length of the span, and the overall condition of your deck all play a big role in the structural integrity of your pergola. Generally, for a pergola like yours, especially without a center support, you’ll need a robust beam—possibly engineered or steel—to prevent sagging.
If you're going for a 20ft span with no support in the middle, you'll need a pretty hefty beam. For my setup, I used an 8x8 oak beam over a 32ft span, and I needed two middle supports for durability. I’d recommend something at least 6x12 for your length, but double-check to make sure it fits your brackets.
Have you thought about placing a post on either side of the door? Instead of three posts, you could use four to support the structure better without blocking your entrance or views.
I was considering a 6x12x20 pressure-treated beam, but the dimensions don’t fit my brackets.