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Eric Wettschreck

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Mrs. Boilerguy announced the other day that she wants a greenhouse out by the garden for next spring. I’m thinking this is pretty cool. Me being me I’m not going to go out and buy one, I’m gonna build it. Again, me being me, I’m going to build a permanent structure that I can also store my mower and other stuff in it during the winter. I’ve seen them built out of aluminum framing so I priced out 1 x 1 aluminum tube to weld together and good golly is that stuff spensive. Now I’m thinking of just green treated lumber frame and polycarbonate sheets, like sun lights for pole buildings. Does anyone out there have any experience with greenhouses and their framing? Would green treated lumber be a bad thing?

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PVC seems to be a pretty common way to go, I saw one where they used PVC

bows and bolted/screwed that same corrugated fiberglass on top with roll

up sides of sheet plastic so you can ventilate on hot days. Way cheaper

than aluminum. They used 1x2 ceder on the edge of the sheets so as to have

a good surface to attach the sheeting. Probably not as pretty but still

gets the job done. smile

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Most greenhouses today are made out of galvanized steel and are covered with a simple poly film. Typically the poly is attached using channel lock and wiggle wire.

I've got 3 greenhouses at my place. One is a Atlas lean-to 16x24 made out of galvanized steel square tubing and double wall polycarbonate panels screwed to the frame with aluminum flashing for the edges and seams. The other two are large hoop-houses made out of bent galvanized tubing with the simple covering of poly film secured by channel (wire) lock and wiggle wire. Covering with poly film is much easier than sheeting, when all is said and done it looks pretty nice too.

Do a search for wiggle wire and it'll get you thinking in the right direction. Pretty sure treated lumber could work. Cedar might be a good option too.

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I would shy away from green treated lumber and use cedar which is naturally rot resistant and doesn't contain the same nasty chemicals. I remember on on New Yankee Workshop a while ago on PBS he built one out of cedar, and corrugated poly. He also installed some automatic window openers. The openers used spring steel so no electricity and easier to control the temp.

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Just wondering if you couldn't go to a place and find some old storm windows or something like that and build one out of recycled material for very little cost. I know nothing about greenhouses so I suppose there's a reason other than aesthetics.

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I've bodged together some greenhouses in my day... And here's some of the things I've learned.

It's almost impossible to build a perfect greenhouse straight out of your own head. If you buy a commerically produced kit then someone else has already thought through the problems with venting, heating, R-Factor.

I can tell you that "Green Treat and Polycarbonate" is a good way to go that won't look as Ghetto as my last "Old windows, scrap lumber and plywood" greenhouse.

BUT I know exactly what I want to do now when I get to my new location.

I know... I know... The idea of dropping a couple hundred into something just to "Learn from your mistakes" the first couple of years sounds wasteful and you'll probably just want to "Think your way through it" and hope for the best.

So here are tips to keep in mind.

Framing wise... It's just like you were building a basic garden shed with shingles except your roof and the top 4-6 feet of your walls will be over lapping polycarbonate. (Just read all the rules on assembling polycarbonate) wink

The bottom 2-3 feet you will want solid wood, and insulate it to as your cold air will pool below.

In your design you will want to make sure you have a way to vent hot air near the peak. (Better to do this in the point of the A of the roofline than in the actual roof from a "Structural" stand point... But you'll get better ventilation from a skylight vent.

You'll want electrical run out to it because without air circulation for the venting it'll just become a swamp that cooks out the seedlings in late april/early may.

(On a sunny day my greenhouse can get over 110 if I don't open the venting in the morning.

You'll also want to be able to store copious amounts of water both for watering seedlings but also as a heat sink for deep freak cold snaps etc...

(Which means you have to rig everything so that water and electrical NEVER meet.)


Placement in the yard is also essential... It's better to have the house running north-south than east west.

You'll want to find some kind of sun shade for the walls and roof... Direct clear polycarb will cook the seedlings just like an ant under a magnifying glass.

Now if all of the above sounds daunting for a first crack at it...

I would google "Building a hoop house." Which is PVC and cloudy plastic... It's pretty dirt cheap to build... You can take this year on the chin learning about the environment the plants respond best to and then tackle serious plans next year.

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Thanks, this is good info everyone.

Me being me I don't go half way. This will be a perm structure in my yard and I don't want it to look like a crack house. Plus, I want to use it in the winter for storage for lawn mowers and such, so it'll be a real building and not a hoop house wrapped in plastic.

I didn't think aboot the cool air dropping, now I do.

I was planning on trenching power and H2O to it already but thanks for the tip.

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Well... A hoop house is a seasonal structure that you can learn from.

Your biggest enemy is too much heat...

I start my seedlings indoors in march and then move them out in April... So the cold isn't much of a big deal.

Keep in mind the bigger you build this thing though the harder it will be to manage the cold when some rogue cold snap comes in. My Greenhouse is essentially an 8X8...

I've tested it down to 25 degrees without frost damage simply by putting a 3 gallon stock pot of boiling water in there when I went to bed at night. Because not only does it put out heat, but it acts as a heat sink itself. Because plants within 3-4 feet of the pot can't get frost damage until the water in the pot freezes.

So if you build some 12X12 monstrosity and some nasty 21 degree cold snap hits you'll be fighting it a lot harder than an 8X8!

Now depending on how much money you are willing to spend on electrical you can always get one of those portable oil filled radiators and set it in there at 50-ish degrees.

At the same time on warm & sunny days if you don't keep the heat down and provide air circulation, you'll end up with plants that leg-out and/or worse, fungus and mold... And believe me once you get a fungus growing on a greehouse plant and you put that plant in the garden, that fungus will in time spread to your entire garden.

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