Building a Lean-To Greenhouse

iris2sun(7 NC)January 2, 2007

We are planning on building a small lean-to greenhouse (about 6 ft wide, 12 ft long, 8 feet tall) that will be attached to a shed which has exterior siding and a door. The lean-to will be south facing and used mostly for plant propagation in fall, winter & spring. We're in zone 7. Since this is our first attempt, we are looking to build a low-cost greenhouse. We have several questions, but I'll post them one at a time.

1. We are considering using either gray electric conduit pipes or white pvc pipes for the framework of the structure. Are there any specific advantages or disadvantages for using either type of pipes? Also, is there a problem with using the white pvc connectors (like T's etc) with the gray electric conduit pipes.

Thank you for your help.

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maineman(z5a ME)


" there a problem with using the white PVC connectors (like T's etc) with the gray electric conduit pipes?"

I've never actually made that kind of connection, but I would be concerned that the PVC Cement might not bond as well to the steel conduit. The PVC Cement is designed to bond PVC to PVC and I think it works by slightly dissolving the PVC of both pieces so that they "melt" together to make a good bond. Since the PVC Cement can't dissolve the galvanized steel of the gray electric conduit, the intended kind of bond couldn't occur.

Another disadvantage of that kind of connection would be the difference of thermal expansion between the two materials. My guess would be that steel expands more in hot weather than PVC and that the steel contracts more in cold weather than PVC. That might tend to break any bond that the PVC Cement did form.

Just out of curiosity, what are planning to cover your greenhouse with?


    Bookmark   January 2, 2007 at 11:13AM
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Use the metal conduit not the plastic or the PVC.

I built a 16 X 20 greenhouse using 3/4inch metal conduit with the heavy duty connecters and it works great.

    Bookmark   January 2, 2007 at 12:09PM
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nathanhurst(VIC Aust)

Yeah, PVC is not a good GH construction material - it sags and attacks PE film. Use wood or steel.

    Bookmark   January 2, 2007 at 12:28PM
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iris2sun(7 NC)

The gray electrical conduit pipes that we saw at home depot are pvc. In reading postings from various forums, I gathered that the gray pvc is sun resistant and the white is not and so is more likely to grow brittle.

One responder indicated that pvc pipe degrades the greenhouse film. Is this problem caused by high temperatures like in the summer? Since we are in NC, and are not planning on growing anything in the greenhouse during the summer, we were planning on taking the greenhouse film down.

Another question we had. We were planning on using wide greenhouse film as our covering, but were wondering if forum members had a recommendation as to the best place to purchase it. There are so many web sites that offer it.

Thanks again for the comments.

    Bookmark   January 2, 2007 at 12:52PM
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Hello, newbie here,I'm in the process of building almost the exact same gh here in oklahoma,zone 7. I'll be interested in the answers the experts here give. I'm using a simple wood and screw framing,then painting to protect it. Lancsindustries is selling 12 and 20 mil double polished clear pvc sheeting for about 2 dollars a lineral foot. It's 54" wide, uv resistant ,cold and heat tolerant,I'm thinking of the 20 mil, 20 yards for 139 dollars. Wounder if 20 mil is too heavy of something?


    Bookmark   January 2, 2007 at 8:22PM
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nathanhurst(VIC Aust)

Nothing to do with heat, the PVC plasticisers make PE go brittle within 6months. That's with the grey stuff. Painting the PVC with an inert paint (acrylic) may be sufficient. But the high environmental cost of PVC production and the poor structural strength make it a bad idea in general. (I know, I built one out of PVC pipe + PE film many years ago)

Use steel tube + PE film if you want a cheap and reliable solution.

    Bookmark   January 2, 2007 at 9:37PM
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stressbaby(z6 MO)

There was someone who posted wildly here for a few weeks, then kind of went away, who was crazy about her metal pipe "bender" that she got on ebay. It might be worth looking at.

    Bookmark   January 3, 2007 at 12:43AM
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Hello stressbaby

Hi All,

I did go away for a while. Still just as excided about my greenhouse as I was the first day. I've been in hospital most of the time. Everything is ok now. Expect a full recovery before spring gets here, can't wait to get back to working the farm. I spend as much time in my greenhouse as possible now. This is my first post since being home. I do miss my new freinds here and will try to post more often. Yes the people on ebay selling the greenhouse tubing benders use the ebay ID 'TIPPERGOAT' we purchased a second bender from them not long ago.
They have a new website its

Here is a link that might be useful: tool for bending greenhouse hoops

    Bookmark   January 4, 2007 at 4:16PM
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maineman(z5a ME)

I have my doubts that a conventional hoop greenhouse is suitable as a lean-to.


    Bookmark   January 6, 2007 at 1:37PM
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I would avoid using plastic for any structural purposes. After 3 years of annual greenhouse projects, I've seen many cases of plastic degradation.

    Bookmark   January 7, 2007 at 6:42PM
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maineman(z5a ME)


"I would avoid using plastic for any structural purposes."

That's why I stopped looking at Rion greenhouses. Our resin lawn chairs became very brittle in only two years of outdoor exposure and literally shattered at the least provocation. I would be very concerned about even brand new resin plastic in the zero-degree temperatures that are common here during the winter.


    Bookmark   January 7, 2007 at 9:26PM
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