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    • CommentAuthornstansbury
    • CommentTimeJul 3rd 2017 edited
     
    They've been mentioned here in passing, and seem to be used extensively in more enlightened parts of the world, but I can't find any suppliers in the UK for them.

    Some background:

    https://www.aecb.net/forum/index.php?topic=1778.0
    https://www.youtube.com/watch?v=VHF74HQPZtM


    In the US & Canada there seems to be:

    https://www.carterlumber.com/styrofoamtm-brand-duramatetm-plus-insulation-18524
    http://insulation.owenscorning.ca/builders/products/foamsealr.aspx
    http://www.conservationtechnology.com/building_gaskets.html

    This is the closest thing I've found in the UK but it doesn't mention much about it: https://obexuk.com/product/cortex-epdm-bubble-gasket/

    The last option seems to roll my own from these guys as it is a closed cell self-adhesive, although it's not in a continuous roll:

    http://www.monomer.co.uk/expanded-epdm-sheet-6mm-thick.html
    http://www.martins-rubber.co.uk/products/rubber-gaskets/epdm-sponge-gaskets/

    Anyone got any concrete recommendations?

    Cheers
    •  
      CommentAuthordjh
    • CommentTimeJul 3rd 2017
     
    You could try asking Dow, or Owens Corning, or Trelleborg (who make the Conservation Technology stuff, which also looks like the Cortex product) about distribution in the UK, or perhaps buying it abroad and importing it. Certainly ask Obex for their price. It's definitely possible to buy rolls of butyl rubber tape in this country, including self-adhesive, and it may be possible to buy other tapes.
  1.  
    Yeah Amazon.com sell a selection in the US I could get hold of - just seems a pain if there's a known supplier in the UK.
    • CommentAuthorMike1
    • CommentTimeJul 4th 2017 edited
     
    I've used EPDM thermal insulation tape in timber-to-brick/concrete situations. The roll I have here (50mm wide x 2mm thick, adhesive coated one side) is unbranded, but it fairly readily available in the UK and is normally used for pipe insulation.

    While it's not intended for airtightness it seems to do a good job, and EPDM is resistant to common chemicals, UV light, moisture, etc.
  2.  
    Just use spray can foam on the concrete before you put down the frame.
    •  
      CommentAuthordjh
    • CommentTimeJul 5th 2017
     
    Spray can foam doesn't stay flexible after it cures and cracks can open up. Except of course for special spray can foams designed for air sealing.
    •  
      CommentAuthorSteamyTea
    • CommentTimeJul 6th 2017
     
    I used to use a foaming agent for polyester resins, also used a plasticiser that made the resin quite rubbery. Never tried the two together, but it would be a cheap 'liquid' solution.
    • CommentAuthorowlman
    • CommentTimeJul 6th 2017
     
    Expanding closed cell neoprene type tape is readily available. Most suppliers slit it to order, so easy to specify your own widths. It's available in many different expansion bracket thicknesses.
    • CommentAuthortony
    • CommentTimeJul 6th 2017
     
    Are we saying that all sole are draughty?
  3.  
    Posted By: djhSpray can foam doesn't stay flexible after it cures and cracks can open up. Except of course for special spray can foams designed for air sealing.
    Why does it need to stay flexible and why would it crack if it never moves for the next 50 years?
    Fitting gaskets and dpc's beneath the sole-plate gives 2 surfaces for air leakage to occur, you've to seal between the sole-plate and the gasket and between the gasket and the concrete.
    When installing Twin-Studs on Passive-Slabs a line of foam is sprayed on the concrete when the sole-plate's installed. The foam seals and glues the sole-plate to the concrete creating an airtight gasket, we've eliminated the requirement for tapes in this zone.
    An anti-capillary layer of compacted crushed stone's installed beneath the Passive Slab, the EPS is anti-capillary and a Radon barrier's fitted making the concrete a dry zone so no gasket or dpc is necessary.
    •  
      CommentAuthordjh
    • CommentTimeJul 6th 2017
     
    Posted By: Viking HouseWhy does it need to stay flexible and why would it crack if it never moves for the next 50 years?

    Because timber and concrete move differently both when the humidity changes and when the temperature changes. As well as expansion and contraction, wood can bow and twist.

    The whole point of gaskets is to make the seal, not create the need for more sealing! They've been used for a long time in places like Sweden and Canada as well as the US and I would trust them a lot more than builders foam myself.

    In my case though we went for tape to seal the floor to wall junction.
  4.  
    Posted By: djh Because timber and concrete move differently both when the humidity changes and when the temperature changes. As well as expansion and contraction, wood can bow and twist.
    Timber can move a bit but not in this case, the sole-plate's anchored to the concrete every 1-2m and the entire weight of the house is sitting on it which prevents movement. Its in a dry controlled environment, the humidity and temperature of kiln dried treated sole plate inside a dry timber frame wall has little annual temperature or humidity variation.
    PU foam like a foam gasket is flexible but neither will move beneath the anchored sole plate of a heavy wall.

    Posted By: djhThe whole point of gaskets is to make the seal, not create the need for more sealing!
    Explain what you mean by seal? What's the gasket doing that foam isn't? If the gasket is used Neil will still need to tape the frame to the concrete for an airtight house or in your own words he'll "create the need for more sealing!". If foam is used he won't need to use tape, I know this because we do it every day.

    Posted By: djhThey've been used for a long time in places like Sweden and Canada as well as the US and I would trust them a lot more than builders foam myself.
    Trust them to do what exactly? The majority of houses in Sweden are built on Insulated Raft Foundations, gaskets are rarely used because concrete with a radon barrier beneath is deemed a dry zone.

    Posted By: djh In my case though we went for tape to seal the floor to wall junction.
    Questions have been raised here before on the longevity and de-lamination of tapes, how long will the tape last when in your own words "timber and concrete move differently both when the humidity changes and when the temperature changes. As well as expansion and contraction, wood can bow and twist"?

    Here's an image from Tom Foster of PU foam being used to seal between OSB sheets as an airtightness layer.
    PU Foam between the sole plate and the floor has a similar benefit.
      Foamed OSB.jpg
    • CommentAuthorjfb
    • CommentTimeJul 6th 2017
     
    just checking - by PU foam you mean expanding PU glue? That is what is used on Tom's example not normal expanding foam.
    •  
      CommentAuthordjh
    • CommentTimeJul 6th 2017
     
    I'm not going to say any more on this subject. I just ask people to do their own research in the published literature before deciding how to make seals in their own buildings.
  5.  
    Posted By: jfbjust checking - by PU foam you mean expanding PU glue? That is what is used on Tom's example not normal expanding foam.
    Thanks John, you're correct Tom used Expanding PU glue and we've been using low expansion foam with a gun to vary the output, so they're different PU products but similar in some respects. Is it that one has a blowing agent and the other foams when in contact with air? I've also used Tom's expanding PU glue for making furniture, they look similar when they dried into my overalls.
    Its much easier to pull a trigger for the PU foam than squeeze expanding PU glue out of a bottle, so I wouldn't consider using expanding PU Glue beneath a sole-plate.
    • CommentAuthorjfb
    • CommentTimeJul 7th 2017
     
    yes they can be a nightmare to squeeze out - cut the hole in the lid bigger than you think! And if you don't finish the bottle you usually get a crust to deal with.
    The glue needs exposure to water (probably air as well?) to go off.
    Foaming is a lot easier.
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