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Building up joists to lay down loft boarding

I've just had my loft re-insulated. I unscrewed all the boarding I had up there and emptied the loft, they came along and laid down the insulation (one layer in between the joists and then another layer perpendicular to that). I want to put the boarding back down now but the insulation is too high.

So... the way I see it I have 4 options
1. Strip the insulation down to just one layer for the area I want to board and then board it as it was before, traight on to the joists
- The previously boarded area was large though (approx half the entire loft area) and I'd rather keep the same area
2. Increase the height of the joists to just above the insulation
a) by screwing new joists/beams into the sides of the existing joists
- will this work (an image of what I mean is here)
b) by laying new joists/beams down perpendicular to the existing joists
- seems like a lot of wood would be needed (and hence a lot of cost)
3. Change the insulation under the bit I want to board with thinner insulation.
- too expensive

Can anyone help with some advice? What's usually done in this situation?
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Comments

  • SPANIEL36
    SPANIEL36 Posts: 1,905 Forumite
    i think what your trying to achieve is what i've already got done. what i ended up doing was increasing the height of the joists by screwing more timber onto the top or the sides of the existing joists (i cant remember which one) then screwing the boards down onto of them. there was a lot of screwing involved (my other half has just piped up with a cheeky grin the dirty minded so n so)
  • harryharp
    harryharp Posts: 1,215
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    We are having our loft insulated in a couple of weeks time and are going to be faced with the same problem if we want to continue using the loft for storage.

    The company that's doing the work also said that we'd need to raise the height of the joists. Does anyone know if this is a DIY job (if so, how diffficult is it and how much does it cost?) Or does it have to be done by a builder?
  • Canucklehead
    Canucklehead Posts: 6,254 Forumite
    Hi
    This is just one thread, on the subject, out of a few http://forums.moneysavingexpert.com/showthread.html?t=410399&highlight=insulating+loft

    Note the link in post 3 ,there are other versions of this Wickes being one.

    Corgi Guy.
    Ask to see CIPHE (Chartered Institute of Plumbing & Heating Engineering)
  • harryharp
    harryharp Posts: 1,215
    First Anniversary Combo Breaker
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    Hi
    This is just one thread, on the subject, out of a few http://forums.moneysavingexpert.com/showthread.html?t=410399&highlight=insulating+loft

    Note the link in post 3 ,there are other versions of this Wickes being one.

    Corgi Guy.
    Many thanks Canucklehead. Should we be raising the joists BEFORE we get the insulation done then? Also the link in post 3 says 'Page not found'- any chance of another link- cheers.
  • Canucklehead
    Canucklehead Posts: 6,254 Forumite
    harryharp wrote: »
    Many thanks Canucklehead. Should we be raising the joists BEFORE we get the insulation done then? Also the link in post 3 says 'Page not found'- any chance of another link- cheers.
    Yes. Updated link here... http://www.knaufinsulation.co.uk/products/polyfoam_xps/polyfoam_pitched_roofing/polyfoam_supadeck.aspx

    HTH

    Corgi Guy
    Ask to see CIPHE (Chartered Institute of Plumbing & Heating Engineering)
  • isofa
    isofa Posts: 6,091 Forumite
    You can also buy insulating boarding, which might be worth a look, B+Q does it: Knauf Space Board Loft Board Insulation (T)52.5mm but it's quite expensive.

    I've boarded nearly all of the loft, but not increased the insulation, but instead I've carpeted most of it with carpet we replaced from rooms in the house, so although probably not as good as thick new insulation, the boarding and carpet (plus all the stored boxes!) must have added some further insulation, and a massive storage area to boot.

    Don't squash down insulation to fit boards, you just reduce it's heat trapping effect, also don't put any insulation under the water tanks, unless you want them to freeze in the winter!

    It's probably easier to raise the joists now, although I imagine cross beams would be a better idea, as it'll distribute weight better, as the roof joists aren't as strong as those on the living areas of a house.
  • Poppycat
    Poppycat Posts: 19,913
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    We had our loft done in Summer on a grant I spoke to Energy trust regarding this matter and they told me to raise the height of the joists and it should be fine. However the company who laid the insulation refused to lay all the insulation between the joists they lay some of it the other way too, they said that that is the only way they were allowed to do it, so there was little point in increasing the height of the joists

    Also bare in mind by increasing the height of the joists and laying boards with increase weight, some modern lofts apparently need structural alterations to take the weight.

    That knaufinsulation superdeck is very expensive by the way
  • harryharp
    harryharp Posts: 1,215
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    Poppycat wrote: »
    We had our loft done in Summer on a grant I spoke to Energy trust regarding this matter and they told me to raise the height of the joists and it should be fine. However the company who laid the insulation refused to lay all the insulation between the joists they lay some of it the other way too, they said that that is the only way they were allowed to do it, so there was little point in increasing the height of the joists

    Also bare in mind by increasing the height of the joists and laying boards with increase weight, some modern lofts apparently need structural alterations to take the weight.

    That knaufinsulation superdeck is very expensive by the way
    So what you're saying is if you get loft insulation done (with the usual type of insulation), you can't use the loft for storage. From what you've said I assume you don't use your loft for storage?

    We're getting ours done with a grant too. I'm not sure what to do, as we have a lot of boxes up there.
  • Poppycat
    Poppycat Posts: 19,913
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    Yes that is what I got told by the insulation company apparently its all down to the DTi who pay for the grant work. Yet the government quango Energy saving trust said it was okay to increase height of the joists it shouldn't be a problem.

    You could of course undo the work and increase the joists

    I do use the loft for storage this week only for Christmas tree/decorations but I wanted the loft boarded up to have more storage
  • isofa
    isofa Posts: 6,091 Forumite
    You do have to be careful about adding too much weight to the loft floor, but increasing the joists won't add that much, it's the heavy chipboard boarding that has more of an impact, but if you use larger sheets the weight is well distributed. Always screw the boards down, to avoid nasty accidents. We store masses in our loft and couldn't manage without it.

    However it's also worth noting how the area storing the water tanks is reinforced with heavy wooden cross beams, nothing you are going to store in the loft is going to be as heavy as a full water tank!

    If you are going to store heavy things up there, make sure you put them above the walls below, rather than in the middle of ceilings, and spread things out!
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