Hi,

If I am picturing this correctly... You could simply use the metal conduit clamps to secure the conduit to the 2x8 with. You may be able to drill holes and tap in rebar for you conduit to slip over. I think I would go with 4x4's, drill holes using a spade bit, and put the conduit into the holes.

I did something similar with my cold frame..

Regards,

Stephen

A treated 2x6 is a standard baseboard. Anchor it with stakes or posts driven into the ground. The corners are the most important, as your end hoops will receive the most force against them from the wind.

If you want your sides to raise up for ventilation, you'll need a "hip board" down each side, which is typically a 2x4. The plastic attaches permanently to the hip board. Below that, it is typically held down with weights or clamps. Stringing a zig-zagged rope along the sides for billow control is a popular idea. That prevents the wind from pushing the plastic inward.

Both suggestions are good advice. You need to anchor your baseboard (2x8) at regular intervals, not necessarity within the couduit. Rebar is common but you could consider fence posts that provide better "Grab" to the ground, and more importantly, would allow you to sink a screw or insert a bolt through the post and baseboard to hold the foundation down. You could also dig corner cedar posts(2x8 would suffice) 30-36" deep and anchor to them.

All the base strengthening can remain once your PVC fails.

I think all the above mentioned would work fine. I have designed greenhouses and hoophouses utilizing the frame to contain the pvc pipe rather than re-bar. By creating this framework I was able to gain more head room and with flip out vents on the bottom I have extended the size of the greenhouse.

Here is another picture from this winter. This has survived without any issues in Northern Michigan. Our snowfall total is typically several feet (not all at once), but the greenhouse has held a lot of snow on it.