EPDM - OSB 3 decking 3mm expansion gap - needed on T&G?

21 Jul 2004
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United Kingdom
Hi All,

Going to be laying new decking for an EPDM covering.

Been reading that a 3mm expansion gap should be kept between the boards.

Using T&G OSB this will not be possible. Is that OK and is it due to an expansion gap already being present in the T&G?

Also if I use normal boards, without the T&G and I put the 3mm expansion gap between all the boards, what happens over the joints when the rubber goes on. Will it cause visible lines between the joints when the rubber is glued down and dries?

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Bit confused here.

Are you talking about normal decking?
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Thanks chaps,

So I've decided to use the T&G boards rather than the larger 8*4 sheets.

Does each joint where the two t&g boards meet need to be resting on the middle of a joist? Or will the T&G support the boards in areas where it does not fall in the middle of a joist?
You don't need to find a joist with osb t&g, I always lay at least three boards down before nailing to make sure they are lined up.

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