Roofing for flat pergola?

rjjencke

Hi guys, new to the forum but have been reading for a very long time.

Anyway, I built a pergola and have been thinking of adding corrugated roofing panels to the top, on top of the 2x4s that are currently on the top.

However, I built the joists level so the top is pretty much perfectly flat. I am in Arizona where it barely ever rains. Would this be a bad idea to put roofing panels on top with no slope?

I want to add the roof for 2 reasons: Shade and to protect the treated lumber on top. Its difficult to apply a wood preservative up there with my spa below and in my way. Thoughts?

Daniel Holzman

In your case, a roof poses a few issues. First off, the roof greatly increases the probability of structural failure in a windstorm, specifically the roof coming off, or taking the framing with it if it comes off. You probably don't have snow load issues unless you live in the mountains, but wind definitely needs to be accounted for.

I realize it does not rain too often, but no one ever builds a perfectly flat roof, it would not drain. There is a small, carefully controlled pitch even on a "flat" roof. I have no idea if there are building codes in your area, or if you are subject to any, but you certainly should evaluate if the framing is adequate to support a roof before you go about installing one.