OSB Expansion and contraction do I leave a gap?

OSB Expansion and contraction do I leave a gap?

Expansion and contraction in OSB is not a problem ( I think)

As far as I know, no gaps needed in 18mm T+G OSB the expansion is built-in. The lower part of the T+G this doesn’t meet the other side; however, the top use so I don’t understand how that works! I know they are moving over to a new under T+G soon, but that’s all I know. I’ve tried reading the BS EN 1995-1-1:2004+A1:2008 Eurocode 5:  ( 145 pages but went to sleep)

Tongue and groove OSB

Tongue and groove do I leave expansion joints

The expansion per meter if it gets damp is recorded at.03mm so it’s not much
we always leave a perimeter gape of 10 mm and push the bards together lightly; some never go tight as the edges are fragile and brake and bind.
I’ve covered roofs over 100 m² and never had a problem, that said we don’t put rigid roofing material on the roof its normally rubber. I get lots of complaints from people that have had GRP glass reinforced plastic flat roofs installed. They constantly complain about the banging noise that comes from the contraction and expansion. Nobody seems to know if this is because of how the boards have been fitted or if its because the GRP is too rigid.

In the past we have cut grooves into noisy GRP flat roofs, then backfilled with an expansion joint. This has certainly improved the situation, but reports back from customers have been fixed some have reported that the banging noise has gon away some say its got slightly better.

It’s still unknown if an expansion joint was placed between the boards, would this still happen, theoretically the ridged GRP would hold the bards other solidly, so expansion or no expansion joint the area is still too big and solid.



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Comments (3)

  • graeme Kyle Reply

    Hi Steven, we have a new GRP flat roof on our recently built extension. It is a warm roof structure and it has a parapet wall to 3 sides. There is a 25mm expansion gap around the upper OSB deck. The upper deck, Kingspan insulation and lower OSB deck are secured to the joists with extra long screws installed every 2 feet. We are getting chronic thumping and banging coming from the roof with the noises appearing to come from the upper structure (upper deck/GRP/parapets). In winter this did not occur too often. Any advice for us before we rip the whole thing off and rebuild it!? Thanks

    15th April 2023 at 8:52 am
    • Steven Dickinson Reply

      sorry for the late reply I get so much spam on this that is really hard to find the real people who need help. However I’m here now if you need help still please just email email me speak soon

      19th August 2023 at 8:55 pm
  • JMCC Roofing Services Reply

    I found this article very informative about “Roofing Services”. Looking forward for more informative articles like this

    19th June 2023 at 2:57 pm

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