Sealant/Putty on a Polycarbonate/Aluminium framed Greenhouse?

Discussion in 'Greenhouse Growing' started by Grum Tum, Mar 12, 2019.

  1. Grum Tum

    Grum Tum Gardener

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    So I got an 8x8 aluminium framed greenhouse with polycarbonate panes a few years ago, and it's been a great wee thing. I had a few issues at the beginning with the panels blowing out in high winds, but I put it down to not having enough clips, so I bought more and that done the trick.
    The recent high winds however, blew them out again- Living in Scotland, high winds are just something that happens, no escaping, so I was thinking of a more permanent solution.
    I was wondering if anyone had had any success using a sealant, and if so, which would you say is best?
    I was thinking of the stuff you put around your bath and shower, but I'm not sure if that would hold up outside in the elements?

    Any advice would be greatly appreciated
     
  2. john558

    john558 Gardener

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    You could try a little Gorilla Glue, you can buy a small pot at Wilko's.
     
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    • CanadianLori

      CanadianLori Total Gardener

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      When I had the twinwall polycarbonate panels in one of my greenhojses, those panels that are flat, I finally used clear 4" adhesive tape. Around the edges and onto the aluminium. It was meant for greenhouses so never slipped off.

      I've always like the super clear panels which I know are less effective but they have a lip on all sides that grip inside the channels and so I replaced the dual wall. Hmmm, now you've reminded me that I still have all the old panels. Perhaps a redo of rhe cold frame might work!

      Anyway, bottom line, the strong clear tape meant for window sealing or greenhouses is a good solution.
       
    • ricky101

      ricky101 Super Gardener

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      Think the real problem with single thickness polycarb is it flexes too much and pulls out beneath the fixings.

      Though I have never tried it, perhaps one or two aluminium angles etc screwed on the inside of the glazing bars across the middle of the sheet, might keep it more rigid.

      I have replaced most glass with 10mm twinwall polycarb and it was fitted with a bead of clear Builders Silicone ( most diy places , screwfix, toolstation etc) followed by the wire type of glazing clips and its stayed in place for about 10 years against wind and footballs , the latter being the reason I had to replace the broken glass.

      The downside of twinwall is it reduces the sunlight slighty and you cannot see the plants inside as clearly.
      An upside is it keeps the greenhouse a lot warmer in winter / reduces any heating needed.
       
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      • Grum Tum

        Grum Tum Gardener

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        I think mine is twinwall? It's got the two faces with vertical lines in the middle of them?
         
      • Grum Tum

        Grum Tum Gardener

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        Not very good at descriptions, but this. That is twinwall, isn't it?
         

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        • mazambo

          mazambo Gardener

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          • Grum Tum

            Grum Tum Gardener

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            Thanks, so how do I put it on? Half on the panel, half on the aluminium? Yeah?
            Is a silicone sealant not good? I am thinking a silicone sealant would be easier to apply?
             
          • mazambo

            mazambo Gardener

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            Yes half and half, sealant is just as good there's some good waterproof ones out there.
             
          • ricky101

            ricky101 Super Gardener

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            Have any panels blown out during last nights storm ? just checked mine and all ok.

            Think for your area you need a belt and bracers approach.

            As my pic shows I had removed the rubber glazing seal , cleaned the aluminium then applied a bead of silicone to it and then placed the polycab onto it , securing with the wire glazing clips, which still just fit
            You could make a neater job than me if you use masking tape to prevent it spreading too far.

            Though I earlier said Builders Silicone, which should be fine, think I may have used HA6 Aquarium silicone, widely available on Ebay for around £4 a cartridge.

            I would then use that tape @mazambo recommends on the outside of the frame.

            Fitting some aluminium angle on the inside say every 610mm should keep it more stable and even adding some angle or neater looking box section on the outside with self tappers etc so if it did break loose they would hopefully retain it.

            IMG_1060.JPG
             
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            • CanadianLori

              CanadianLori Total Gardener

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              Yes, the sealant looks good. I chose to switch to tape because I am lousy at caulking and when I tried it, it looked awful. Plus, the silicone does "break into" the surface of the sheeting so if you make a boo boo and try to wipe it off, forget it. There's a permanent mark. Did this on a clear panel - lost my balance and got silicone where it wasn't wanted. Then had to order a new panel and take the greenhouse apart and ...:doh:
               
            • ricky101

              ricky101 Super Gardener

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              Thats strange, usually find any stray silicone can be peeled off without leaving any marks.

              Any stubborn silicone can be removed with Turps /White Spirit, useful if on clothing.

              Best way to fix it without a mess is to place masking tape on the sheet and frame, once brought together and clipped in, run your wet finger or spatula over the silicone to produce an even finish, then carefully remove the masking tape before it starts to set, job done. :)
               
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              • CanadianLori

                CanadianLori Total Gardener

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                Turpentine or paint remover or whatever, it does damage polycarbonate. I have a sheet of it with the marks to prove it. I simply do not recommend caulking anything if one does not the skills to do so in a tidy fashion. Been there done it and regretted it because I am absolutely lousy at it plus my greenhouse on two sides had to be reached between spindles that support the deck railing. :)

                It's all a personal choice but as I say, the tape is the easiest. Half on the plastic, half on the aluminium.
                 
              • Redwing

                Redwing Wild Gardener

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                I have one of these greenhouses with twin wall polycarbonate sheets. We knew it was flimsy so reinforced it with extra aluminium and used waterproof silicone sealer as well. Still panels have blown out. It’s quite windy here. We’ve done several repairs and more reinforcing. Next time will try that tape in @mazambo s link above. Sounds like a good suggestion.

                On the subject of polycarbonate greenhouses, does anyone know if limewash shading works on the polycarbonate?
                 
              • ricky101

                ricky101 Super Gardener

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                More often here in the uk White Spirit ,aka Turpentine substitute, is stocked by our diy stores and have just been out and used it on some of our polycarb sheets and it brings it up really nice and clean.
                Even rubbing and removing some old hard silicone still comes up ok without any marks.

                Perhaps some subtle differences in uk / ca products ?
                 
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