Loft insulation and flooring

Discussion in 'Builders' Talk' started by kimono, Oct 22, 2007.

  1. kimono

    kimono New Member

    I am planning to replace some tatty loft insulation and then lay loft boards (Wickes) over the joists, to provide a cleaner storage area. The Wickes project guide recommends either using a total 270mm depth of insulation roll in the joist gaps, or (ideally) filling the gaps between joists with 100mm and then cross-laying 170mm at a right angle over the joists. Because my joists are less than 270mm deep, either method would mean my loft boards will sit directly on the insulation. I gather from posts on this forum that this will cause 2 issues:

    1. Squeezing air out of the insulation - makes it less effective.

    2. Removing opportunity for air to flow over the insulation roll surface - causes condensation.

    Any advice on how I should proceed?
     
  2. mikejoiner

    mikejoiner Member

    sorry to say but normal trusses are not designed to be floored , only attic trusses.you could always build up you existing trusses by fixing timbers on top but anything more than a couple of inches might be a bit unstable.
     
  3. refurb

    refurb New Member

    Hi
    I would give D & G a call. The regs are right 270mm, you must cross lay the top up to prevent straight joints. You cannot board over 270mm unless you raise the floor joists high enough to accomodate the insulation and then board. D & G will give you a free survey & there are grants for the top up & the platforms. What area are you in?
     
  4. kimono

    kimono New Member

    Thanks for the speedy replies. Am afraid the term "trusses" means little to me in this context. Am surprised that this is less than straightforward. Excuse my ignorance, but who are D&G? Is this likely to be expensive?

    cheers
     
  5. yeah, I wanna know who/what 'D&G' are too
     
  6. Trog

    Trog New Member

    D&G = Dolce & Gabbana. Jeez you lot don't you know nuffink
     
  7. refurb

    refurb New Member

    Sorry, fell asleep watching DIY SOS, Domestic & General Insulation Ltd, they do most of the grant work for the local councils. The grant depends on what size loft, the platforms are fitted at the follwing, 8 x 2, 8 x 4, 8 x 6, 8 x 8 etc. Usual cost for full roof is around £269.00 fitted with certificate with platforms on top. What size platform?
     
  8. Swiss Tony

    Swiss Tony New Member

    A few years ago 100mm was sufficient insulation and now its 270mm. If you have less than 270mm you will lose some heat.

    How much does that bother you?

    Are you going to lay boarding over the whole loft?

    Would you be happy to have 100mm beneath the boards and 270mm elsewhere?

    You could put some insulation up by the rafters instead of, or as well as the floor.

    I presume you currently have 100mm, so are you bothered about heat loss, or just tidying up your loft.

    The regs won't apply to you, so think about them but don't feel you have to comply.

    Its all carbon footprint, green farty nonsense, so be like me and remove all insulation and turn the heating up just to annoy the government. Just watch out for the polar ice cap melting which may be my fault, or it could be China, India and America combined, or just nature. Blame me if you like. Am I bovvered?
     
  9. ceejj

    ceejj New Member

    Why not put Kingspan/celotex (100mm) between joists and fasten loftboards to existing. Bit more cost/lot less hassle!
     
  10. Swiss Tony

    Swiss Tony New Member

    If you did that, and its a big increase in cost, you may as well put the kingspan between the rafters and have a useable space in the loft.

    Depending on your requirements, it may be worth the additional cost to do this though.
     
  11. J.T. Builders Ltd

    J.T. Builders Ltd New Member

    you all won't like this, but here goes.


    - Clean out the loft, sweep between the joists etc.

    - lay 100mm rockwool between joists.

    -then put new 4x2 joists on top of the exsisting joists, but in the oppisite direction, so they are at right angles.

    - then screw the 4x2's down.

    - then lay another 100mm of rockwool on top.

    - then lay the flooring on top.

    ok so its not 270mm but better then nowt.

    hth
     
  12. Mr. Handyandy

    Mr. Handyandy Screwfix Select

    you all won't like this, but here goes.


    - Clean out the loft, sweep between the joists etc.

    - lay 100mm rockwool between joists.

    -then put new 4x2 joists on top of the exsisting
    joists, but in the oppisite direction, so they are at
    right angles.

    - then screw the 4x2's down.

    - then lay another 100mm of rockwool on top.

    - then lay the flooring on top.

    ok so its not 270mm but better then nowt.

    hth




    The problem with that is you will be adding all the weight of the new joists AND the flooring , to the old joists(which if only 100mm is worse) and not really a good idea. Sorry.


    Now, if you had high ceilings below, there might be an idea there(but not the one above)................




    Mr. HandyAndy - really
     
  13. Measure2cut1

    Measure2cut1 New Member

    I did that in my old house. 150mm cross joists and 150mm rockwool with boards on top. And 300mm of rockwool in the eaves, except the ventilation gap as I only boarded the centre bit. The cross joists help spread the load and it was no problem. The flooring adds some insulation too. After all wood is an insulator and it reduces drafts so there is less air change in the rockwool so it stays warmer too.

    M2C1
     

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