What are you growing that will be 15 feet tall? Trees?

Here is my suggestion, scrap all the connectors, that is what make a PVC tunnel weak. You would have to have probably 40 feet of pipe for each hoop. IMO, you are pushing the limits of this product for PVC.

My new steel framed high tunnel in 30 by 48 and is only 13'6'' a the peak. The bows are almost 40 feet long. That is how I came up with the 40 foot length.

If you want to make it out of PVC,then build a 5-8 foot tall side wall of 4 by 4's and 2 by 4's and then push you pipes into the ground and then also attach them to the 2 by 4 5 -8 feet in the air. Then do the same on each side.

Here is a picture of my new high tunnel going over the smaller one. I am going to be moving the smaller one soon.

{{gwi:311294}}

Here is a picture of the framing that I am suggesting.

{{gwi:287185}}

The hoop is 20 feet, so yours would be twice a big. The width of this building is 18' 6".

Good Luck.

Here is a link that might be useful: PVC High tunnel with 34 foot hoops

It's for banana trees :)

The largest varieties I have (or will be getting) will top out at 15 including the leaves; the smaller varieties will be planted along the edges.

Thank you for the link and advice,
Keith

Keith,

If you can't raise the ceiling, then lower the floor!

What about digging a pit and putting your tunnel over it?

Just another idea.

Jay

A great idea, but unfortunately our water table is about 6" below surface; I ended up using retaining wall blocks and leveled with soil to level out the target area so that at least the lowest wall would be a little further above the water table.

Another idea I'm considering (although this would double the amount of PVC needed) is to use 40' or 50' pieces for my upper loop, then place the regular angled anchors outside of my floorplan and bolt the taller pieces to the well-anchored wider pieces. I could then even put plastic on those side pieces and use it as an area to start some plants early (although that also means redigging the drainage which was put in to capture the water coming off the 20' space, which would now potentially be another 10' out)

I attached a link to a poorly drawn visual of what I'm thinking about :)

http://img827.imageshack.us/img827/8749/ghas.jpg

Or alternatively, should I skip the pvc and move directly to metal? Are there any (free) resources out there that talk about the size of metal piping needed for different width greenhouses?

Many thanks,
Keith

Keith,
I went the same route you did and had the same results with the wind. I then went to Home Depot and purchsed 2x4's, 1x3's and 1x2's and built a wood frame that is screwed together with drywall screws that way I can take it down in the spring.
The basics of the greenhouse were square boxes screwed together. One side wall is 8 foot and the other is 7 foot so the water drains off.
It was real easy making the frame of the GH and I covered it with 2 layers of 4 ml plastic.
The cost of plastic vs wood? Wood cost me $40 more and is much stronger. I can also build more cubicals and add onto the the GH alot easier with wood.
If you want more details and pictures send me an email.

Mike

Thank Mike for the information and offer to share pictures. I'm trying to minimize my total wood area because I won't be using pressure treated wood and will probably have to replace it every 2 years.

I'll start a new thread on the minimum required conduit diameter vs size of greenhouse, since that isn't aligned with this thread's title.

Best,
Keith