Loft legs question

Discussion in 'Carpenters' Talk' started by J d, Jul 4, 2018.

  1. J d

    J d Member


    I moved into my house 10 months ago and ever since has been one nightmare after another. Thats my introduction over.

    Ive had a guy board my loft out in a fashion. He used wood called CLS and ran this kind of over the top of the wooden joists then added chipboard. its hard to explain but these CLS sit on something at each end thats part of the original wooden structure and because they are not thick enough they flex and then in turn the chip board flexes. The insulation wasn't super thick as it was and it didn't run tight in-between the joists. The CLS probably adds 4" as a rough guess, so just takes the insulation without compressing it...maybe? I looked up the new regulation of 270mm and we are not close to that.

    So with all the above, i went out and bought loft legs and i was gong to get the same guy to redo. His response was that you cant walk on loft legs and they are only for storing thing on.

    What do you guys think of the above? I apologise if it doesn't make much sense.
  2. AlvyChippy

    AlvyChippy Active Member

    You are forgiven
    (Made no sense)
    Post pics?
  3. J d

    J d Member

    Ok, i'll try upload on in a min. I've just been up and taken a picture of the worst part. that part where there isn't any chip board.
    Last edited: Jul 4, 2018
  4. J d

    J d Member

    I've just realised i dont know how to up load a pic on this site, i thought i could just pull it from my computer but its asking for a URL?
  5. AlvyChippy

    AlvyChippy Active Member

  6. J d

    J d Member

  7. Dr Bodgit

    Dr Bodgit Super Member

    Sounds like a bit of a bodge, those timbers look to be placed rather loosely over the top of the joists with perhaps 100mm insulation in between, are those original joists 3" deep?

    There is always going to be a challenge in a loft to have both (a) adequate insulation and (b) storage space, especially if the roof slope is shallow with limited head room. Put 270mm insulation down and there'll be very limited space left. Loft legs, if installed well so they can't move, might just take a persons weight but its stretching it.

    The way I did it is in this thread

    - 3" original joists with 2" x 2" screwed on top, takes 100mm insulation (Knuaf earthwool) with chipboard floor on.
    - then in the roof, batten out the 3" rafters with 2" x 2" again, gives around 125mm depth, enough for 70mm PIR insulation and 50mm air gap. Stapled airtec double over to act as VCL and sealed with alu tape.
    The combination of these 2 insulation layers is roughly equal to 270mm of rockwool.

    It took a lot of time, sweat and effort but is now a great place to store stuff, nice even year round temperature and dust free.
    AlvyChippy likes this.
  8. Pollowick

    Pollowick Screwfix Select

    What are you doing up there? Having a loft dance?

    It may not be perfect, but without packing out every joist to provide extra support, you will always get flexing and for lofts which are normally just for storage it should be fine. - the original part of my house uses 4x2 for the ground floor joists and yes a little flexing but I know it is safe.

    There is also no requirement to increase insulation levels. the chipboard also helps form a barrier to the flow of air. Just insulate up to that point.
  9. rogerk101

    rogerk101 Screwfix Select

    I've done something similar by doubling up each ceiling joist with another 2X4 sitting on top of it. This gives me 200mm of insulation thickness as opposed to the 100mm which I was able to have before doubling up. Yes, it took away some of the very useful loft space I used to have, but that's the compromise you make when you want better thermal efficiency.

    There is no requirement for 270mm of insulation in an old house ... it's only a requirement in a new build or a new extension or loft conversion.

    But one thing for sure is that 200mm of insulation is a whole lot better than 100mm.

    The problem the original poster has is that the installer didn't put in enough supports in the first place ... they were too wide apart, causing too much flex on the boards ... especially if the boards are only 18mm thick. Things will get a lot worse when you use extension legs because whereas you now have linear loading, your legs will create point loading, so expect a lot more flex. (I used 22mm chipboard in my loft and it's rock solid. (Yes, if there was enough head height, you could have a disco dance floor up there!)
  10. goldenboy

    goldenboy Super Member

    Loft legs are fine for providing a bit of storage when insulation is laid over the joists.

    Quicker, cheaper and much lighter than using loads of CLS or 4x2.

    You just need to be careful about where you join the boards to ensure support.

    Often have to rip the t+g off and put strips of flooring under with screws and pu glue to join them.

    Definitely for storage rather than jumping around on though.

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