Quoted:
I was reading through posts about the Harbor Freight greenhouse a couple weeks ago. One recurring theme I see is they reinforce the HFGH with conduit. Why couldn't you get some 1" conduit bent up for the junctions and then run PVC for the long runs? Then you are not worrying about the PVC shattering. Just a thought.
Yep, you could do that... in fact a number of places sell tubing/conduit hoop-house frames as a kit. But as I started tallying up the costs and other pros & cons (like lateral stability, ease of attaching different coverings, going with a double-layer w/airspace cover, etc.) a wood frame started looking more and more attractive. I could tell as soon as we got started erecting the PVC frame that it wanted to sway, as a unit, frontwards and backwards (perpendicular to the ribs), so I was going to have to string some wire along the exterior to act as lateral bracing. The plastic would have helped with that once it was attached, but overall I just wasn't getting a good impression of the long term stability of the thing.
All was not lost though. I just came back in the house from helping the wife use the salvaged pieces of the greenhouse frame to build a 16'x12' covered arch shade for our chicken run.
It held up fine for that, since we weren't bending the ribs into anywhere near as tight a radius as we were with the greenhouse.
I think the wood-framed greenhouse will be an interesting project too. The only real complication is the roof, and I've got some ideas to pre-build some 2-by and plywood trusses to help with that. Rough plan: