Really flexible silicone ?

Discussion in 'Motorhome Chat' started by Charlie, Aug 9, 2016.

  1. Charlie

    Charlie Funster

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    Odd question here..

    I need some really really flexible white silicone. In short it to fill a gap between a UPVC trim and a ceiling that is on a large conservatory roof . The roof is extensively lined and extremely well insulated so wht happens is the structure expands far quicker than the main building so the gap opens up.

    I have fitted UPVC trims down the sloping joints and now need to tidy up the very tight gap with white silicone. But it needs to be ultra flexible and it needs to remain flexible or it will not only look rubbish but could pull the plaster on the ceiling as well giving me much work.

    The UPVC trim is fixed to the wall not the ceiling so when the roof expands the ceiling moves and the trim on the wall stays fixed.

    I have asked mates in the trade but looking for opinions before deciding which brand or type to go with.

    Cheers !
     
  2. Speve

    Speve Funster

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    Dow Corning was always the best one when I was working in the trade make sure you get one that has mildew protection in it.
    The one used for showers and bathrooms.(y)
     
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  3. Charlie

    Charlie Funster

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    Thanks ! Dow Corning was the very name that sprung to mind .. But I know on this forum there is much talk of Sikaflex. I realise there are lots of types for different applications but in this case its a joint that literally opens every time the sun beats down on the roof.
     
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  4. Steve N Tracy

    Steve N Tracy Funster

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  5. Charlie

    Charlie Funster

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    Wow that looks incredible ! It does look like more of an adhesive though ? But the claim is one product does it all where most makers of these products have several which can get confusing !

    Thanks !!
     
  6. rogher

    rogher Funster

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    I cannot help here but would like to expand the question: Would this requirement be for a high or low modulus selant?
     
  7. jenny and mitch

    jenny and mitch Funster

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    Some advert Steve N Tracy.
    Mitch. (y)
     
  8. Charlie

    Charlie Funster

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    It is some advert ! I have looked at reviews of CT1 mostly on Amazon and the main thing with it is it discolours badly.. That and it is extremely hard to work with hence my comment above it being an adhesive rather than a gap filling expandable sealant.

    I will look closer though and again my thanks for the link !
     
  9. Speve

    Speve Funster

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    @Charlie you need low modulus it accommodates more movement.(y)
     
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  10. rogher

    rogher Funster

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    Thanks, Alan. That's what I needed to know.
     
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  11. Charlie

    Charlie Funster

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    Yes I thought it was low modulous .. 43 years in construction but hardly ever used silicone or much in the way of sealants... Cheers.
     
  12. John Laidler

    John Laidler Funster

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    You can get so called flexible gap fillers but they are mostly for filling gaps such as between a skirting board and a wall and I doubt these can cope for the movement required.

    Does the gap need to be actually watertight? If not it might be possible to create a sort of sliding joint with uPVC. With a right angled section against the wall and a flat section stuck to the sealing.

    Alternatively, a foam draft excluder wedged into the gap, possibly covered with a strip of something, depending on how the conservatory is constructed.
     
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  13. pappajohn

    pappajohn Funster Life Member

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    And that answers the question......an all in one HAS to forfeit some qualities to let others work.

    You can't have a product which is very flexible for one job (ie: bath silicon) yet rigid enough for another job.(ie: no nails)

    One product for one situation only.....the way to go..
     
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  14. Diabalo

    Diabalo Funster

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    Wow that's some MH if it's got a conservatory.
     
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  15. Mattyjwr

    Mattyjwr Funster Life Member

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    I read it that the Op has a sliding joint system with uPVC strips but wants to fill the very small gap between this uPVC (on the wall) and the conservatory.
     
  16. Geo

    Geo Trader - Funster

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    No, its for a Swift hence the need for underwater setting
    The above is for the amusement of those who have never owned a swift
     
  17. Charlie

    Charlie Funster

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    I did what you suggested.. When I put the strip up I stuck a thin white foam strip along the top edge to fill the gap and thought it would fill it and allow for the expansion and contraction rate differences. It looke absolutely woefull and didn't work anyway so I took it off.

    No it's not required to be watertight it's for aesthetics only. Of course it's fair to say am I going to sit looking at it but I am just so fussy I can't live with it as it is .. It's better than the awful jagged crack that was there before but not perfect.

    Decorators caulking would not last at all . They claim flexibility but there is almost none even with the super expensive brands.
     
  18. Charlie

    Charlie Funster

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    My thoughts exactly which is why I don't think it's quite the right one. I need a flexible gap filler not an adhesive. I think an adhesive could create a problem as it would join the two elements which are now not tied to each other .
     
  19. Speve

    Speve Funster

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    @Charlie the other option is to glue the strip to the ceiling but not to the walls thus when expansion occurs it stays with ceiling still covering the gap,
     
  20. Charlie

    Charlie Funster

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    What I have used is 40mm UPVC architrave which actually looks fine. It blends in with the ceiling a treat but its only 6mm thick so fixing it to the top edge would not be possible. It is fixed to the wall with 1mm thick white double sided tape which I applied neatly so it runs along the bottom edge. Those that have seen it say it looks bob on except the tiny gap along the top where it meets the ceiling..

    I have spoken today to a fellow builder in a more specialised area than me who has recommended Sikaflex EBT. So I will get a tube and do a short line and see how it goes.

    Cheers mate ! And cheers to those who have advised !
     
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