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Hi Hank. I'd try to breeze through some of your questions, but first of all, do you know there's a whole forum here about greenhouses? Definitely take alook at that. Here's the link:
I've had a thread going there and on several other greenhouse forums for a while. I thought it would be smart to consult some real builders and not just my fellow growers.
Well, I'm not a real builder but I'll try to answer a few questions anyway, and I'm sure claypa or someone else will jump in and correct me if I'm wrong on anything.
2. Drying the wood: It's not really drying per se, but I would let it acclimate for a day or two in the area you're going to be building. But keep in mind that wood, especially when it's outside where you can't control the conditions very well, is going to expand and contract on a regular basis with changes in temperature and humidity so make sure your design allows for this.
4. Staining/painting: Pressure treated lumber doesn't need to be stained/sealed, but if you don't like the color and wanted to stain it then I can't think of any reason why you couldn't.
5. Fasteners: I would probably opt for screws rather than nails to hold the frame together. And I would use galvanized ones since this is for outdoors, you don't want them to rust.
6. I don't think pressure treated wood is going to really be any more work than redwood/cedar, so it's really up to you. For any parts that are going to be directly in contact with the ground, I would use the pressure treated lumber, but for the rest of the greenhouse you could use either one.
I'm surprised you didn't get much help in the greenhouse forum, but your question about the poly carbonate is pretty specific, I guess nobody but Horseshoe knows about it
1 & 2 &6 This will depend on how the frame is designed. Also, you can leave room for warping so your panels don't get stressed, and caulk around them? Not sure. Buy dry lumber, and be selective when you buy it. If you have to store it after you buy it, don't lay it on concrete. Moisture will condense on the wood and warp it. Stack it on sticks to get air around the lumber if you have to store it.
Treated lumber is a lot harder to cut than cedar or redwood, but if you're not making fancy cuts, like rabbets for your panels, it's up to you - you could make it real pretty, say if it's going right where you'd see it all the time, or if it's going out in the 'back forty' maybe it doesn't matter...
I've seen some good deals on Cypress in the last few months, I was really surprised. It comes down to how much you're willing to spend, and what's available. Keep your eyes out for scraps of a wood called 'Ipe' . (pronounced 'I Pay' or 'ee-pay', not sure.) It's a very hard, extremely durable, expensive tropical wood that's being used for decks and railings, it's ideal for outdoor building. I save every little scrap I can find.
3. Anything you can do to preserve the wood will help - paint, stain, even linseed oil, but it might not be really necessary with treated lumber. It gets to the question of how long do you expect the greenhose to last. Same thing with your hardware, #5: you could go all out and use bronze marine stuff or stainless, or use galvanized which is a lot more economical, just not as pretty.
Lots of choices! Are you working from an existing plan? I'm curious to see exactly what you have in mind.
I wish I had room for a greenhouse, my basement looks like a wreck right now, with little plants growing on the available shelves, and I STILL have to put away all the Christmas stuff...
I might go try to bump your greenhouse threads up
I use pressure treat a lot.
It (and all wood) will warp guaranteed, so as they said above ...allow for this.
A GH is going to be high humidity, outside not so humid.
If you double glaze you must also allow for humidity between the panes of glass.
Use either weep holes or a drain specially made for wood windows .
I use silicon chalk.
I don't find it any harder to work than most #2 pine.
You do though need to let it sit and dry a bit if you're getting it from say HD or Lowes.
Some 4 x 4's I've gotten weight almost 50% more than others as they are being fast tracked into the stores.
Also wear a mask when cutting, never burn the wood and if your working w/ the wet stuff... goggles.
If you get a splinter make sure you get it ALL out.
They fester up pretty quickly.
Screws... Galvanized will rust just not as fast. If you put them in PT I think the Zinc reacts w/ the chemicals.
Try unscrewing one that's been in a deck for 4 or 5 years. Usually they just break off.
I use stainless steel or ceramic coated ones.
The later are FAR cheaper
I just used regular pine, two coats of prime and two coats of good oil based paint on my Porch GH.
But it's walls are totally vertical so the rain isn't a big factor.
HD, being on the coast, can't you get cypress easily and cheap? Even if you had to have a sawmill slice it for you, and then sticker it and store for a year to dry out, you'd have a better material.
I agree with the guys above, warping is inevitable... as a general rule. When I sticker wood to dry, I leave about an inch between boards side to side, put small wood pieces about 1" x 1" about every 3 feet on top, and then another layer. Be sure to cover the top from rain but leave the sides open. Under cover is obviously best, and it can take a year depending on water content of the green wood and the average ambient humidity in the surrounding air.
Ric, I haven't seen ceramic coated screws. Tell me more about them? I switched to square drive ss screws for outdoor projects a few years ago.
Ceramic coating 'may' be the wrong term... they may be powder coated... the coating is called Evercoat in Deckmate Screws and Durafast in Phillips II.
I've had them out for 5 years now in PT wood and no rusting...
I too love the #2 Square Drive's... maybe 1 in 100 strip out... Phillips...1 in 4
