I'm planning to build a 100 sq ft greenhouse. The structure will be out of regular 2" x 4" lumber painted with a low VOC exterior Behr Ultra paint. It will have 28" X 76" panes of recycled tempered glass. The top section will be screened to provide air circulation. The main purpose of the greenhouse will be to provide rain shelter for my tomato plants and some added heat. I will also be growing my grapevines in the greenhouse to prevent raccoons from eating every single grape in the fall! I am fortunate enough to have an ignoring sprinkler line that I can also tap into. My question is with regards to the base. I live in a relative frost-free area and was thinking about using 4"x4" or 6"x6" lumber. I'm assuming that pressure treated lumber is not a good idea for a vegetable garden. Is that so? What about cedar? Would I be ok to bury a few rows of cedar without being concerned with rot? I need my base to be at least 6" below grade to discourage raccoons from tunneling into the greenhouse. Thanks Mike
Correct do not use treated woods for any garden you plan on growing edible produce from. I've always heard untreated redwood will be the longest lasting choice. Also probably the most expensive in the short term but over time it pays for itself. -Luke
In regards to your base for the walls. My neighbor has a 30+ year old compost box made of yellow cedar and its still doing fine. Redwood is rare, for a reason here in B.C. as we have good access to cedar. Try Whonnock for a source.
To discourage rodents, raccoons, etc., it is best to put wire screen in a trench beside the greenhouse base. Fold the screen ninety degrees about 2/3 of the way down with the fold facing outwards. Rodents/raccoons are too stupid to try to dig back outwards, and then down to get under the screen. They'll give up and find another way in:)
What are you considering for a roofing material? If you're going with glass, you should be aware that the first really big hailstorm you get, or even the first windstorm strong enough to knock twigs/branches out of the trees, will finish your roof off. The new clear polycarbonates, however, are fantastic, and I can attest that they'll stand up to even tropical hailstorms.
Tempered glass is tough. Especially if it is 1/4" thick. I wouldn't worry about anything breaking it. That's what car side windows are made of, and they're very tough to break, and car windows are not even 1/4" thick.
I'd still want to err on the side of caution. I've had tempered glass greenhouse rooves break on me in the conditions I mentioned....
