There's the rub. Til you invest in the treated wood and clamps and then purchase the wire-lock base for a good seal you will realize that you are essentially putting a high-class stereo system in a Yugo. Start with a quality galvanized metal frame and the add-on materials will be lifetime investments.

I have played with pvc for framing i have concluded that it is really only useful for very smaĺl structures
It is also expensive for what you get in comparison to nearly every other option when you calc sqare foot cost, at least what i encounteŕed.

I have played with pvc for framing i have concluded that it is really only useul for very smaĺl structures
It is also expensive for what you get in comparison to nearly every other option when you calc sqare foot cost, at least what i encounteŕed.

I have played with pvc for framing i have concluded that it is really only useul for very smaĺl structures
It is also expensive for what you get in comparison to nearly every other option when you calc sqare foot cost, at least what i encounteŕed.

The plastic attaches to either the wood base boards, or the wood hip boards if you have roll-up sides.

I like chain link top rail a lot better than pvc.

I've had a PVC hoophouse for the 6-7 years. It is 12x15. I'm hoping to retire her this year and get a greenhouse (likely a RIGA). Here are my thoughts:

(1) I used sunlight protected PVC - conduit (gray colored)
(2) My "ribs" for the PVC are every 3 feet.
(3) My ridge was PVC cut into just under 3 foot lengths and attached with first 4-way connectors and later these other connectors where you can set the angle (google "PVC 1" Adjustable Ell Fitting 4 Way"). I went with the latter when I wanted my hoophouse to stay up all winter here in Massachusetts to reduce my need to wipe snow off (it survived the winter with no snow removal on my part).
(4) My end walls were made out of wood and I added a hip board on the outside of the pvc (screwed to the pvc) and a baseboard. I used wiggle wire to attach to the hip board. At the base I didn't have wiggle wire - but I had a roll-up bar that weighed enough to keep the plastic glazing down.
(5) Only for your roll up sides do you "clamp" down the plastic glazing with clamps on the ends (google snap clamps - these are also used also for row covers).
(6) On the endwalls design and install your window/door. I used automatic vents for BOTH of these in the spring. (The door was on the leeward side of the prevailing winds)
(7) Attach the plastic glazing on the end walls in wiggle-wire channels and on the long hip-boards. At the ends have roll-up pipes (we just had another piece of pvc conduit that we rolled up).
(8) We ran electricity to the hoop house for emergency heating (small space heater and/or lights).

I primarily used this hoophouse as a early season starter in the spring. I would unroll the glazing (it was stored rolled up on one of the hipboards) and secure it in the wiggle wire channels. Then once summer hit I would put it all away again. (I left the endwalls covered in plastic since that was screwed into the wood endwall frame/door/window). Without the plastic glazing over the top the hoophouse doesn't seem stable (side to side) but with it the hoophouse is stable.

What I didn't like about this setup:
* Manual ventilation. I couldn't go anywhere unless I wanted my plants to freeze or bake in the spring. I had to roll up my sides and roll them back down. My automatic openers on the door/window were no where near sufficient to keep temps down on a sunny day in the spring (even if it is only 40 outside).
* the inevitable rips in the glazing - you had to tape them (not a huge deal)
* this set up was very drafty. It was hard to seal the door/window and the roll-up sides against air leaks.
* I hated attaching the glazing in the winter or putting it away in the spring. It was a two person job to roll it over the top of the greenhouse while securing it as you go. (It probably only took a couple of hours max).

What I liked:
* I was planting in-ground in March in MA
* I had a nice place to grow my seedlings in April in MA
* I got to experiment with what I would want in either a future coldframe or greenhouse.

What I would do differently if I was to stay with this setup:
* Put in larger window(s) on the end walls to improve my ability to automatically ventilate without needing power
* consider having one knee wall (for me this would be on the north side) be constructed of wood to allow for automatic ventilation on that side and/or easier insulation to reduce heat loss.

When I used it for winter gardening (which I loved) I also put in foam insulation board about 1 ft deep along the outside edges.

What are you planning on using your PVC frame for? What you do will depend on that.