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Remedial action on insulated loft

Discussion in 'Roofing and Guttering' started by DavidRP, 8 Jun 2015.

  1. DavidRP

    DavidRP

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    Location:
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    We have just had builders in to insulate our loft, putting celotex between the rafters. The job went badly as the temperature in the roof went up. We have become increasingly worried about what has been done, and we want to work out what we need to do to put it right. We have parted company with the contractor and settled (probably quite a bit in his favour considering, but life's too short...).

    I want to identify what needs to be done to remedy the problem. Not interested in identifying that the builder is to blame (because he clearly is - but we are glad he is gone). Not interested in going legal. Just remedy.

    I phoned celotex - but it is difficult to get a "common sense" view. Not a criticism - its their job to stay with best practice.

    Could I ask for your advice?

    1) 1930s brick built detached house with clay tiled roof nailed to battens. Felt underneath is a fabric (not impermeable - and I could feel air passing through). General condition of the roof is dry and the roof is apparently in good condition. The fabric is original I would think and in one place only there was some hanging down so I could see tiles. Generally the loft gets very hot in summer, and very cold in winter. I can feel air passing through the fabric into the loft. The house is a drafty house - and is expensive to heat.

    2) Boarded floor of loft with very old insulation underneath - about 1cm worth. Two externally ventilated bathrooms underneath loft with non-LED downlighters, and no board or insulation around them/over them. Covered cold tank and uncovered expansion tank for heating. Boarded floor for storage prevented insulation being built up at ceiling level.

    3) Builder bought 70mm celotex board and has installed between rafters. Battens not fitted "because there was not enough room" - so the board is installed against the felt. Generally insulation not well fitted with gaps along rafters (which are uneven distance apart). Insulation tight against plate, but stops short of the eaves at the bottom. There is no "drape space" (between insulation and felt) and there is no vapour control layer. There is some expanded foam used to fill gaps between the boards and the rafters, but this is token. In most of the loft there would appear to be 2.5 cm of gap between board and bottom of rafters - which would enable a drape space of 2.5 cm behind if board was edged forward). In some areas the gap is less - suggesting the board either not pushed up against the fabric throughout - although it seems to be solid, or something is behind getting in the way. I am guessing from the depth of insulation which I can measure from offcuts and this gap at the front, that the rafters are 4 inches deep.

    4) We suggested to Celotex that we could:

    - Try to ease out the boards, add battens to create the required drape space of 50mm - but they said that was not recommended.
    - Add battens and deepen the rafters by an additional 2.5cm which he said we could do try.
    - We asked if the boards should be all the way to the bottom of the eaves (tight on eaves) and he said we would need to seek advice of a contractor (ho hum).
    - Celotex suggested that we could remove the boards entirely and position on top of the rafters (but they have been cut to the uneven width of the gap between rafters and foamed - so we are not keen)
    - Celotex told us we could add expandable fire safe expanding foam to fill gaps (provided they arent too big)
    - Celotex want 1000 grade polythene as a vapour control layer added.

    5) The loft is covered with blobs of pink foam, but is currently cool and dry. It is early summer, and it gets cold but not freezing each night. I suspect that it is just in the winter when we are really likely to get condensation, if we get it at all. We live in London - and it gets to freezing in winter but rarely below.

    Questions:

    1) Do I need to take drastic action? The old contractor is a roofer, and claimed that the loft would be fine. Is this a case of Celotex protecting against extremes like us generating unusual amounts of condensation/ unsually cold or extreme weather? It is possible that the builder knows what he is talking about, but couldn't be bothered to finish the job.

    2) If I need to take action - what would your recommended course of action be?

    - Make good and finish what has been done so far: We live in London. We have extractor fans in bathrooms. I could swap to LED lights, add boards back over the bathrooms thereby sealing off the sources of humid air. Get lid for expansion tank. I could finish the job of adding foam to make a seal where the gap is small, and replace board where it isn't. I could add some fabric insulation at ceiling level around the perimeter to cover the uninsulated perimeter at ceiling level. Live with the lack of drape space, but check in winter for condensation.

    - Try to ease out the boards, and either leave them proud at front or extend depth of rafters. Add Vapour control layer. The builder suggested (incidentally) if he created a barrier (board over the top of the rafters - he was getting enthusiastic about him returning to do a loft conversion at some future date) then he would either need to add ventilation into the soffit boards or "dot tile ventilators around the roof). He suggested the latter was better.

    - Buy new boards and start afresh. Outlay in materials c.£1750.


    3) Would you add a Vapour Control Layer?

    Advice please! What would a reasonable professional builder do?
     
  2. Cabbyfan

    Cabbyfan

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    I'm not a builder but I currently doing a loft conversion bit by bit. My bungalow is an early 70s with concrete tiles and old bitumen felt. Most of the roof is coming off soon but building control advised any old section left that were to be insulated needed I think a 40mm air gap under the felt. Less than that means poor airflow and timber issues in the future.

    If your roof membrane isn't breathable and the roofer has jammed celotex right under the felt then in my opinion you have a problem.

    The fix is drop it all down and create airflow or take the tiles off and replace the membrane.
     
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  4. ^woody^

    ^woody^

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    Bullet points would be lovely
     
  5. DavidRP

    DavidRP

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    Thanks.

    You are so right, woody. Sorry!
     
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