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General: T&G OSB?

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1 to 17 of 17

  1.  
    • CommentAuthorShevek
    • CommentTimeMar 21st 2013
     
    Would you recommend using T&G OSB for a roof deck?
    • CommentAuthorDarylP
    • CommentTimeMar 22nd 2013
     
    Depends if you can get them up there, what sizes are you planning?
    8 x 4 is possible with two of you....

    Good luck... :smile:
    • CommentAuthorTimber
    • CommentTimeMar 22nd 2013
     
    Below a single ply roof membrane in your roof construction? I wouldn't. It should be fine as a sub deck, but tends to move a bit with changes in moisture and will delaminate if it gets wet. A high quality hardwood plywood would be my choice.
    • CommentAuthorEd Davies
    • CommentTimeMar 22nd 2013
     
    What's the slope? What do you mean by “deck”, below the insulation or on top (sarking)?
  5.  
    yes , OSB 3 smart ply 8/2 or 8/4 are common

    i presume OSB is one off the best boards to in environmental terms, as it's a good use of low quality wood and minimal glue relative to ply etc.
    • CommentAuthorTimSmall
    • CommentTimeMar 22nd 2013
     
    We used SmartPly 2.4m x 0.6m T+G OSB/3 18mm as the sub-deck on the flat roof for our dormer (also as air tight layer), with between 120mm sloping up to 190mm PIR above (Kingspan Therma-taper - cheap from Seconds and Co). The OSB/3 was on top of 600mm centre 170mm joists below, with 10mm sealed void immediately below the OSB/3 (for lateral moisture diffusion), then 150mm PIR infill between joists (checked with wufi). EPDM glued to the top of the therma-taper. Install went very smoothly. I embedded some temp/humidity sensors in there, which hopefully I'll get around to hooking up soon!
    • CommentAuthorNovice1
    • CommentTimeMar 23rd 2013
     
    Have the same dilema deciding on OSB3 18MM. To T&G or not to T&G?

    AFAIK
    Pros
    Better air tightness
    Actually can be sourced in 2400x1220 so less waste and cutting hassle
    Easier install
    Gets rid of problem of unsupported edges

    Cons
    Cost? double

    Am I right? Can anyone think of anything else?
    I am using on a 170m2 flat roof so the cost argument is winning at the mo. Was planning to glue/silicone in between the boards (filling in the the 3mm expansion gap) to help support the edges. Also looking to source drylining metal flat plate to support the edges. Not sure if that is necessary as it may wipe out the cost benefit
    • CommentAuthorShevek
    • CommentTimeMar 23rd 2013
     
    Posted By: Novice1
    Actually can be sourced in 2400x1220 so less waste and cutting hassle

    Is the extra 20 mm the tongue? Is it only tongue and grooved along the long edge?

    Gets rid of problem of unsupported edges

    How do you mean?
  9.  
    Re unsupported edges I imagine Novice means that if it's T and G all round (I think mine was), you can 'flap'. BTW, my local roofing merchant was selling 600 x 2400 (or 2440?) OSB3 much cheaper than I could get any such board (even sq-edged) elsewhere. I have had a bit outside for many months and it shows none of the 'hairyness' exhibited by 11mm OSB in my experience when I've left it out too long.
    • CommentAuthorTimSmall
    • CommentTimeMar 23rd 2013
     
    Posted By: Novice1Cons
    Cost? double


    Around here, I think the circa 600x2400 was something like 10% more per m² than square edge 1200x2400. I did have to shop around a bit to find a supplier which stocked it tho'. As has been said, with the T+G you don't have the same requirement to support all cut edges on joists, or noggins, which is a lot quicker, and cuts waste.
    • CommentAuthorNovice1
    • CommentTimeMar 23rd 2013
     
    do tell do tell
    Where is the cheapest source of OSB3 you guys have found?
    Keen to get a good price. Reckon I need 120 18mm (hopefully 2400x1200 and/or T&G). Also need 150 9mm.
    At those volumes delivery even a few quid off would help.
    So whats the best prices you guys have got on OSB3? (T&G or not)
    Have also called 6 local merchants and no one can source 2400x1200?!!?
    • CommentAuthorShevek
    • CommentTimeJun 5th 2013 edited
     
    Thanks guys. I'm going to go with the 2400x600 T&G OSB3 boards, purely because we can eliminate noggins and fit more insulation. Link to detail below. It's the sub deck layer I need it for.

    £12 +VAT a sheet okay (for 14 sheets)?

    As an aside, what do you think about stopping the sub deck and joining the wall and roof insulation like I've shown? Recipe for problems?

    https://dl.dropboxusercontent.com/s/0t9zgd065h084eq/eaves.pdf?dl=1
    •  
      CommentAuthorfostertom
    • CommentTimeJun 5th 2013
     
    Have you seen http://www.greenbuildingforum.co.uk/forum114/comments.php?DiscussionID=6890&page=3 - major discussions of 18 T&G mastic'd vs 9 sq edged bubble glued and nogged by dryliner's light galv flatstrap/angles, about the middle part of that long thread.
    • CommentAuthorShevek
    • CommentTimeJun 6th 2013 edited
     
    Thanks Tom, although this isn't for our airtightness barrier, this is for the roof deck supporting an EPS/fibreboard composite:

    https://dl.dropboxusercontent.com/s/0t9zgd065h084eq/eaves.pdf?dl=1

    Should we be trying to make that airtight too?
    • CommentAuthorShevek
    • CommentTimeJul 10th 2013
     
    I've just discovered Smartply before ordering standard stuff thankfully.

    I've noticed, however, they have 2-sided or 4-sided tongue and groove. Which one should I go for in the case of a roofing deck? What's the advantages/disadvantages of 4-sided?
    •  
      CommentAuthorfostertom
    • CommentTimeJul 10th 2013
     
    Discovered that Smartply OSB3 (no added formaldehyde) is v much more vapour permeable than 'typical' OSB, presumably being less impregnated with glue. That's good - been using it - but the worry now is that it may also be much less airtight (figures hard to get).
    • CommentAuthorShevek
    • CommentTimeJul 10th 2013
     
    That I'm not too worried about because I'm relying on separate membranes for vapour control and air tightness.

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