Yeah -- building a thin-film greenhouse over a gazebo would be relatively easy (you can build a thin-film over almost anything), but I'd be wary about working with panels on something like this. Perhaps someone with more experience in said construction can help more than me.

If the Gazebo is free standing, I would build up a Base using 4x4's. (This could then be secured to the ground)

Then drop 2 2x6's on each side (creating 3 approximate 4 foot openings on each side.

Then run a 2x4 horizontaly between the 2x6's this would allow additional surface area to attach the paneling to (Hopefully someone can give some ideas on fastening the Poly, perhaps screws with one inch washers)

For the Door, I would drop a vertical 2x4 in one of the 4 foot openings (makeing a three foot opening)(of course there would not be a horizontal 2x4 here)
Then either pick up an aluminum Screen door that you could put a Poly Panel on, or pick up a Storm door, either way just hang the door in the three foot opening.

I would attach the wood to the metal tubing using u-bolts.

But the big problem you are going to run into.... HEAT...

In Here in Zone 9a, I can get temps of over 120 on a cold sunny day, I could easily imagine temps of over 140 in Zone 10.

Over all it would be easier to use Clear poly tarp (not from a Big box store, but Greenhouse Tarp), to make a GH.

From my experiance, you will still need to heat it at night, whether you use poly tarp, or Poly Panels, or have a Very Large Heat Sync

hi
Are you in 10 Florida?? if so don't use any type of solid covering on the walls. Don't use any type of lumber
Even treated will rot before your eyes. The best wall covering is vinyl lattice with or without shade screen.
How do you intend to secure to the ground??
Why can't you grow orchids outdoors?? Have been doing so for over 20 years. Do you intend permanent mounts??
You are keeping warm growers right?? There are many ways to provide temporary cold protection.
With the right structure in the right location you can avoid heating and cooling except on a very temporary basis.
Wilma took out my small shadehouse last year in spite of 4x4 posts set in concrete. My attached shadehouse suffered only minor damage.
I'm thinking of rebuilding but going to give the "frame " a lot more thought lol
in your case would definitely give this a lot of thought unless you intend to dismantle during storms?? gary

Thanks, jimmydo2; I was planning on beefing up the structure with some wood, but hadn't thought of as simple a solution for the door as you suggest! I am concerned about the heat factor. Can you elaborate on the "clear poly tarp", i.e., what is the thickness and where can I find it? Could it be stapled to a wood framework, or how would you attach it?

I think it is officialy called Polyethylene Greenhouse Film. It comes in rolls, and is like 6 Mil Thick (not to be confused with 6MM thick Polly Panels). I place thin trips of wood over the tarp (Sandwiching the tarp between the wood frame and the strips, and then use screws to hold the wood strips on. (staples right into the Poly, would cause the Poly to tear

Gary, I'm in southern cal coastal zone 10. There are a few large orchid growers in my neighborhood, such as Andy's Orchids. They have advised me what can over-winter outside. While it is very rare that I get a frost, it's still too cold for the majority of my collection (I keep a large collection of cymbidiums and epidendrums out year-round, but for the others, only five out of 50 or so plants can handle it.) The collection is varied--species and hybrids: cattleyas, phrags, paphs, phalaenopsis, miltoniopsis,odontocidium, ornithocephalus, laelia, nageliella (aka hartwegia),phaiocalanthe, rhyncholaelia digbyana aka brassavola dig. "mrs. chase", sophronitis, vanda, angraecum, vanilla, bulbophyllum, brassia, cirrhopetalum, dendrobium (phaleanopsis), dendrochilum, encyclia and jumellea.
The greenhouse location will be on a cement patio in a sheltered corner of the yard, which has fencing around it. We don't get many storms that would be strong enough to do any damage.
What are your ideas on providing cold protection? Are your orchids in the shade structures you mention? Can you provide heat without an exhorbitant energy bill? I hope Wilma didn't destroy them as well as your shadehouse.

hi
Horse of a different color lol. Isn't it amazing how much different zone 10 Cal is from Fla.?? I maintain a screenroom,shadehouse,and grow a bunch as garden plants with temporary structures. Or let's say i used to lol.
Frances and Jeanne damaged almost everything but Wilma took them out lol. The state took my orange trees because of disease and I had 50 orchids attached to them. had to move them all in two days!! My only real survivor was the screen room and aviary but you don't keep orchids with parrots lol So I'm trying to rebuild to a structure that works,thought it would be a great time to really have a temp,controlled greenhouse.that really works for the HOTHOUSE i mean Florida lol. Don't mind spending the money but want a structure that works!! had even thought of refrigeration but think I'll stick with warm growers.
Anyway,i could tell you what i do for winter protection
but doubt it would be useful in Cal. even in 10.
Cold is such a temporary thing here counted in hours rather than days but it sure can be enough to be fatal.
if your interested I'll go into detail
Designing a useful greenhouse in this climate is certainly difficult but i have some brilliant ideas and this time I'll get it right LOL
Sorry i couldn't be of more help to you and good luck with your project!!! gary

Gary,
As a fellow zone 10-er, please tell me what your ideas are. I am in desperate need of a "florida greenhouse' and have no idea where to start, especially if heating is necessary.

hello
I've already hijacked gardnergals post enough lol
Probably should start a new thread as i think a useful plant structure in zone 10 florida needs to be entirely different than almost any other areas.
Have been keeping some type of structure for plants for over 20 years and mostly what I've learned is how not to build it lol.
Would love to discuss this with other growers in hot climates.!!! I'm in the process of redoing mine and sofar I'm heading right back to my last "stle" which had several serious flaws.
You want to start a new thread???
gary g