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Thread: Greenhouse Question

  1. #1
    Join Date
    Aug 2001
    Location
    Tex .. near Dallas
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    Question Greenhouse Question

    Have a lot of things I want to do .. and each seems to cost money ... go figure!

    I am going to build a greenhouse before winter and plan to go ahead and put fiberglass on the roof ..... but think I am going to opt. for 6 mm plastic on the sides and add the fiberglass next year. Is 6mm "indutrial quality" .. about as good as it gets? Only needs to last through the winter.

    Jim

  2. #2
    Join Date
    Feb 2002
    Location
    Surrey, BC, Canada
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    6 mil poly

    Jim-we use 6 mil for vapour barrier, and would consider it heavy duty, compared to 3 mil or whatever is the normal duty poly. This will be nice and strong for one winter...I realize you guys can get good winds there otherwise I'd suggest something lighter.

    I'm using 3 mil overwintering poly, supposed to last one winter only, and it handles the wind okay in low tunnels. I think the greenhouse type stuff may have some extra additives to make it tougher, tho, at a given thickness, think I heard others discuss this.

    There is even heavier poly, like 8 mil that can be used for ponds in place of EPDM, but certainly overkill and harder to find...the 6 mil should be great for you. As I recall up here, there is special "vapour barrier" 6 mil that costs extra, I'd look for the cheaper version that doesn't have to satisfy building inspectors.

    Glen in BC

  3. #3
    Join Date
    Jun 2003
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    Bolton, Ont
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    greenhouse question

    Jimtx. I first must say Glen in B.C whats you up to. I havent seen you here or anywhere for a long time, Certainly different with MIKE.

    Jimtx, Getting back. I use 6 mil poly for all my greenhouses. I dont think it comes any thicker, besides it lasts for 5 years.

    Wholesalers use 3 mil, but when april comes they cut holes in them so it doesnt get too hot and burn the new foliage until the crew comes and removes the poly.

    Wholesalers have a crew that only put poly on and remove. Thats a job I wouldnt want, but their probably low paid.

    So if you want a one season poly get 3mil. if your looking at 5 years min use the 6 mil.

    Hope this helps. George.

  4. #4
    Join Date
    Aug 2001
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    Zone 9a - Gulf Coast
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    Oh, Thank you Glen and George for helping Jim with your answers!

    I do want to make sure, though, that Jim and others understand, and please correct me if I am wrong, you are talking about poly film and not the visquine type plastic that you purchase at Lowe's, Home Depot, etc. that is usually marked as 'not for greenhouse' use.

    It has been a long time since we discussed the difference so I feel it is important to at least mention it.

    I can tell you from experience that the true greenhouse plastic will last a long time compared to the visquine type plastic that degrades into tiny pieces if exposed for very long by ultra violet rays (within one year).

    I have had 3 mil clear poly film, true greenhouse plastic on my patio for 2 years now, and it shows no signs of discoloration, wear or tear despite being heavily beaten by rains as well as winter and tropical winds, and I am amazed at the difference. It seems to be more flexible and has more stretch and give as well as strength.

    But, Jim, these are the experts. You listen to them, for all I can tell you is what I am learning....
    Ann B.
    Zone 9a
    Gulf Coast


  5. #5
    Join Date
    Jun 2003
    Location
    Bolton, Ont
    Posts
    149

    Greenhouse question

    Ann, I didnt kmow Home Depot sold Poly. If so I dought its greenhouse poly.

    I purchase mine from the greenhouse manufacturer.
    Jim apparently wants to cut costs, so going to a 8 mil poly will defenately boost the price so much that it wouldnt be worth the difference.

    I've seen a greenhouse similar to what Jim wants to build except it has shade cloth at the sides and plexiglass in the middle.

    I did like that idea but 2 pieces, double the work changed my mind. I would rather use 1 piece of poly.

    I dont know the lenght of the greenhouse, but their sold in 100' rolls. the clear poly has a 5 year UV coating. The white is less.

    My greenhouses are 20'x40' and require a size of 32' wide poly. I believe this is a common size. Jim this is the size I use for mine, but shape of the greenhouse might differ in size and price,
    but I believe the size is a standard size.

    Good luck, George.B

  6. #6
    Join Date
    Aug 2001
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    Zone 9a - Gulf Coast
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    George,

    Our Home Depot and Lowe's do not sell greenhouse poly, and the packages are clearly marked 'not for greenhouse use'. I can only assume that this is because the plastic will not withstand the uv rays. Indeed, this stuff disintegrates in less than a year of our sun and heat.

    The plastic that I used on my patio is 3 mil greenhouse plastic, clear, because my patio is enclosed and gets very little light under the the old pecan trees that are nearby. It is UV rated, and wonderful as far as I am concerned.

    We used to use the other stuff, from Home Depot, but it fell apart in one year's time and didn't let enough light in...

    I purchased the greenhouse uv rated plastic from BWI Company here and a 100' roll of it was relatively inexpensive.

    I am just in awe that today it is just as new and flexible as it was when I originally bought it!

    So, if anyone asks me if there is a difference, I say "YOU BET!"
    Ann B.
    Zone 9a
    Gulf Coast


  7. #7
    Join Date
    Jun 2003
    Location
    NW Oregon
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    30
    Hi, this is my first post here. I am blessed to live in the nursery capital of the modern world, and have the choice of greenhouse construction supplies from at least 5 local suppliers. We use two layers of poly on our greenhouses at work, with a small blower to inflate a "bubble" between them for insulation. I have no idea how many mils, because it is rated for lifespan rather than mils. We took a deep breath and shelled out for the 6-yr poly on two 30x100 houses, and so far it has lasted 8-1/2 years in good condition. We have corrugated fiberglass on a couple of the old propagation houses, and find that it deteriorates fairly rapidly. Corrugated Lexan seems to be becoming popular here on new greenhouses that are for show -- retail gardens etc -- but overall, I would have to say that most nursery folks here (Willamette Valley, Oregon) prefer the poly.

    Susan

  8. #8
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    Aug 2001
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    Tex .. near Dallas
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    Question Poly

    Will the poly be ok for the roof on a leanto greenhouse? Flat side will be against the garage and be teh length of the garage.

    Thanks,

    Jim

  9. #9
    Join Date
    Dec 2002
    Location
    northeast Tennessee
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    Susan,
    Welcome to Landspro. You truly live in a great place for plants. Hope to get lots of info from you.
    Again welcome.
    Jim, I would say the poly would be okay for the roof but you may need a shadecloth depending on how much and when the sun hits it.
    tennessee sue

  10. #10
    Join Date
    Aug 2001
    Location
    Tex .. near Dallas
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    280

    Question Winds

    Have been reading up on installing the poly .. and it seems it is just stretch it over the frame and tie it down. My gut feeling is that I need to "nail" it down ... placing 1" X 2"s over the plastic and nailing it to the frame. Have seen regular plastic come apart in our "light winds" ... and we have had some serious winds this past year.

    I could be wrong ... have been before .... and the plastic may be able to take 60-80 mph winds and if so .. please correct me .. would be a lot easier to build.

    Thanks in advance,

    Jim

  11. #11
    Join Date
    Jun 2003
    Location
    NW Oregon
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    Jim,
    There is a professional greenhouse product that has been on the market about 10 years now called "wire lock". It is a 2" wide track that you fasten to the frame of your greenhouse, and lengths of zig-zag wire that fit inside the track. You install it wherever you would be attaching the edges of your poly. You lay the poly over the track, then fit the wire into the track over the poly. Works like a charm, no wet, rotting lath rolled up in your plastic, no holes through your poly! You may be able to locate it locally, but if nott, check out Oregon Valley Greenhouses on the internet. It's very light-weight, so shipping would probably not be much of an issue. Susan

  12. #12
    Join Date
    Aug 2001
    Location
    Tex .. near Dallas
    Posts
    280

    greenhouse question

    Am going to have to go to the site ... having trouble visualizing this but thanks for the help. As long as I get it finished before winter .... will be a happy camper. I am tired of losing my garage for the winter and think I will be able to space vertical poles just about right for a hammock .. hmmmm ... little music .. cool drink .... mid winter .... nice!!
    Jim

  13. #13
    Join Date
    Jun 2003
    Location
    Bolton, Ont
    Posts
    149

    Greenhouse question

    Silver, You got it.
    Jim I strongly suggest investing in Wirelock. A fantastic product that I have on all my greenhouse, whether shadecloth or poly. The shadecloth doesnt have to be tight but the polylock keeps it secure.

    Nailing poly using straps of wood to hold the poly will eventually come loose. I have an area that I do the exact thing to protect fruit trees. I have an 8'x40' strip of plastic that goes around this area. There are times that I will find a strip of wood on the ground.

    Jim the polylock goes around the front and back hoops. and along the base of the plastic on the sides.

    Jim if the wind gets too strong it will tear the poly. I dought you want to install poly in the middle of DEC/JAN weather.
    I think Im pretty clear. George.

  14. #14
    Join Date
    Aug 2001
    Location
    Tex .. near Dallas
    Posts
    280

    ok ..got it

    Ok .. got it .. one more (probably not the last though ) .. I am making a leanto ...figure rafters with overhang of 3 inches or so .. and then straight down ....... is this going to work? Or, I could make it no overhang and straight down.

    What do u think?

    Jim

  15. #15
    Join Date
    Aug 2001
    Location
    Zone 9a - Gulf Coast
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    Okay, here I go, being 'different' again....

    I have an enclosed patio. It is under the main roof of my home and is 13'X21' and has screen on 2 sides, and triple sliding glass doors on the two inner sides.

    Almost 2 years ago, I got tired of the plastic that you get from Home Depot and Lowes that falls apart into tiny pieces despite the fact that my patio gets dappled shade from the pecan trees and 2 foot eaves.

    I decided to install a product called 'Screen Tight'. I had the challenge of the fact that the patio screen is attached to metal that have grooves in it for the spline to hold the screen tightly in place. I used self tapping zinc screws to install the screen tight.

    Screen Tight used a design similar to the existing metal framing of my patio screening, but offered me the ability to have 2 layers of plastic if I desired. I purchased 'clear', 3 mil greenhouse plastic and installed one layer. It has held up for 2 winters now. I keep saying I am going to remove it, and just leave the screen in place, but I haven't.

    For you see, I have enjoyed not having the rain from severe thunderstorms and tropical storms blow into the patio soaking the floors.

    Granted, the plastic is not as tight as I would have liked and it whips in the strong winds that we sometimes get, but it has held up well, and I would use it again in an instant.

    I think the idea is somewhat the same as the 'Wire Lock', but this looks really nice, and I don't have to worry about rust or corrusion.

    One thing I can say for sure is that if this 3 mil uv rated greenhouse poly has held up to some of these strong winds, I would trust it and the 6 mil on any greenhouse structure I would build. In the long run, it saves you money.

    And, fortunately for me, it is not that much more in cost than the cheap stuff that falls apart....

    Have FUN, JIM! It's a learning experience. That is for sure!
    Ann B.
    Zone 9a
    Gulf Coast


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