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Insulating a Pitched Roof That Has No Felt Installed.

Discussion in 'Roofing and Guttering' started by Teleport, 19 Jul 2006.

  1. Teleport

    Teleport

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    As mentioned in the topic I am looking to insulate a loft space by fixing (probably with a staple gun) a waterproof, breathable layer between the rafters then, some form of insulation, then plasterboard.

    The roof currently consists of only tiles and battens.

    I was thinking this product for the waterproofing
    http://www.screwfix.com/app/sfd/cat/pro.jsp?cId=101893&ts=16163&id=31795

    I'd be grateful for some opinions on this so I know I'm on the right track.
    Any other solutions, methods, products or advice would be apprieciated.

    Thanks[/url]
     
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  3. Roofer

    Roofer

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    There's been lots of previous threads on this subject (with many different opinions).

    If you do install some sort of underlay make sure it is vapour permeable, the screwfix link you gave is for a non permeable.
     
  4. Static

    Static

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    Is it your intension to use the loft as a habitable area?
     
  5. Teleport

    Teleport

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    Eventually, But that's a long way off. I'll be putting a staircase and floor
    joist in when I do. In the mean time I want a insulation solution that will
    comply with regs so that when I do make the area habitable so I don't
    have to rip the lot out and start again!

    This looks ideal for the insulation side of things.

    http://www.screwfix.com/app/sfd/cat...d/cat/pro.jsp?id=76477&slotName=null&homeRef=

    Thanks Roofer. It says it has an absorbant undersurface and is suitable
    for installation where the insulation is at rafter level. Isn't this what I
    need? I need it to stop rain driven between the tiles but allow moisture to
    escape from below, right?
    Can you suggest a product? One that can be tacked to the inside of
    rafters. Any ideas?
     
  6. Roofer

    Roofer

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    No underlay is actually designed to be fixed from underneath but that's not to say it wouldn't be successful.

    Tyvek underlay is a market leader and a good product
     
  7. Teleport

    Teleport

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    Thanks for the recommendation Roofer.

    I'm really only concerned with protecting the insulation and plasterboard not necessarily the tops of the rafters as they're still mainly protected by the tiles. Last thing I want is stains on the boarded out loft space.

    So If I tack u-channels of Tyvek underlay facing into the loft between the rafters, push the insulation up into the channel then board over with 9mm plasterboard. Will that be a permanent solution? And will it comply?

    Thanks.
     
  8. christi

    christi

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    hi im doing same thing in my loft, its just slate and rafters, i just read your post and wondered if it turned out ok? any tips you can provide would be most appreciated, thanks
     
  9. Maxxy

    Maxxy

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    Just out of interest as you've bumped it anyway, is 'water proof and breathable' possible?!?

    If air can go through it surely water can...
     
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  11. noseall

    noseall

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    one thing everyones missing.

    if you fix a waterproof membrane (breathable or otherwise), to the underside of the rafters, and you happen to have a roof leak, then two things will happen.

    a. you will have water pi***ng into your property, down the cavity,round the rafter ends, wall plate etc, rotting everything.

    b. because of the internal membrane you now have no early warning system, thus allowing water ingress for sustained periods of time.

    very dodgy.

    the ideal scenario is tiles, tile battens, breathable membrane, rafters, insulation: between and under draw, plasterboard and skim.
     
  12. christi

    christi

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    sounds dead right to me. anyone fancy supplying a quote to do the above work on a 2up 2down slate roofed victorian mid terrace in norwich ? thanks
     
  13. jeds

    jeds

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    It has to be said. The whole idea of waterproofing and insulating a roof from the inside like this is hopeless and there is no way you can reasonably make it comply with regulations. The foil insulation linked to above is woefully inadequate and will not provide anywhere near the minimum standard.
     
  14. snozzer

    snozzer

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    Forget it, adding roofing felt from underneath is a bodge and will haunt you.

    The felt is there to back up the slates if a slate breaks, if that happens the water runs down the felt and into the guttering, because the felt laps into the guttering. IF the felt is inside where is it going to lap into to discharge any water, I will tell you, nowwhere, it will **** out into the room below, only now instead of a few drips, you will have it all aggragated into 1 channel and it will pour in like a tap.

    If your serious about this, redo the roof. Take the slates off, lathe and felt up using tyvek or simiar (no need to worry about went tiles/ridges which are ££ large), at the same time you could even fit celotex boards between the rafters before putting the felt on (much easier to do as you dont have to carry chuffing great boards through the house)

    Reuse the old slates, or sell them on ebay and use a concrete tile, while your on the roof, check the pointing/stability of any chimneys, clean/repair/replace gutters and of course enjoy the view.

    Its going to cost you a couple of grand, but if you try to bodge the roof from underneath you will waste £500, you may dislodge/crack a slate without knowing, then wake up on a wet February to a cold wet bed (not like a Sunday mornings warm wet bed)

    Remember your whole house is protected at the moment by a little layer of slate nothing else, and while that is good enough, they can and do fail.
     
  15. christi

    christi

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    again, sounds dead right. im convinced. thanks
     
  16. Deluks

    Deluks

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    Interesting debate.
    So if you were to fix celo/k'span boards between the rafters then you'd get the same problems that noseall and snozzer indicate, what with them being foil backed. But if you were planning to do the roof in the near future (a year or so) anyway, why not go for it?

    You can refelt, batten and tile without disturbing what's between the rafters, isn't that right?
     
  17. davebwithane

    davebwithane

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    Hello
    What is the procedure for doing the above ?
    Do you normally cover the roof in tarp and work underneath it ?
    Is it ok to work in strips or do you have to take off all the roof tiles in one go ?
    I'm going to get some quotes to get the work done (west sussex) and I just want to know if it can be done anytime or is Spring/Summer the only time ..
    Cheers
    DB
     
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