Thursday, April 23, 2009

building the greenhouse

I didn't set out to build a greenhouse. I was just going to ease into gardening this year. I built my square foot boxes in an afternoon some weeks ago and laid them out along the south-facing back wall of the house. It was too cold to plant anything so I began toying with covers made of PVC pipe and plastic but it all seemed so awkward. I'd experimented with a pipe and plastic semi-hoop house before and it was a pain in the butt. But the itch to play in the dirt was ferocious and the next thing I knew, I'd constructed a fully framed attached greenhouse!

Well, that's not exactly how it happened. I spent rather a long time in the design phase, vacillating between small and large, cheap and expensive, temporary and permanent, awkward and convenient, fixed-size and extensible, with or without electricity, and I don't know how many other considerations.

What I settled on was something that was fairly large, not too expensive, likely permanent, convenient with respect to multiple entrances and headroom, that could be easily lengthened, with electricity, and that could be tested this year with plastic sheet glazing and then converted to some form of polycarbonate in the future.

I went with a 2 x 4 frame with studs and rafters on 24" centers. It's rock solid.

The ledger board is at 8 feet, and the top plate of the front wall at 6. There's plenty of headroom for me. That's a decision I am pleased to have made.

Length from this end, the west, to the far side of the chimney is 23 feet. Width is about 7.5. This wall could very easily be moved another 8 or 10 feet west, and with a little roof line modification could go beneath the bedroom balcony and another 10 or 15 feet.

At the east end it joins the deck post, which is also one end of the potting area.

I used a pretty expensive semi-gloss outdoor Behr paint. It doesn't need a primer but still took two coats on the rough lumber.

Isaac helped me paint (left handed). Two gallons did the full frame plus one coat on the house wall.

Plastic is regular industrial 4 mil, from a 10 x 100 foot roll. It's stapled, with lath holding it tightly to the wall studs and rafters. We haven't had a serious blow yet but it has held up with no difficulty in 15 - 20 MPH gusts.

I'm very happy that enclosing the entire potting area occurred to me. I worked through all kinds of designs before that obvious idea struck. I built a simple sliding door.

This is looking west from inside the potting area.

Looking east from the west door. There are four roof vents (visible at upper left), and two wall vents.

Painting the interior wall white made an unbelievable difference in overall brightness.

The floor is covered with heavy duty weed block fabric and medium bark. There's quite a lot of unused space for pots or benches, or I could get a lot more square foot footage by running boxes the full length of each wall.

I haven't decided whether to use a multi-wall polycarbonate or a clear corrugated polycarbonate for the permanent glazing. I was thinking that I really wanted the clarity of the corrugated, but have been finding that I enjoy the feeling of being in a different world that the translucent plastic provides. The diffuse lighting of multi-wall will be similar, though with better light transmission, and is probably better for growing anyhow.

I really, really like being inside this thing! I still have to wire the GFCI outlet and look into getting automatic vent openers but other than that it's fully functional.

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