1/8" Gap Between OSB Sheeting To Allow For Expansion? - Roofing/Siding - DIY Home Improvement | DIYChatroom

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Old 12-18-2006, 05:32 PM   #1
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1/8" gap between OSB sheeting to allow for expansion?

I know that when sub flooring with OSB that it is sugested that you leave an expansion gap of 1/8 inch. Do any of you do this for sub roofing. I would guess not ....but would like to know the practice.


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Old 12-18-2006, 05:37 PM   #2
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If you're using "h-clips" then this will do that for you, if not, I put a 2' nail between the sheets for expansion. Actually it has more to do with contraction of the rafter/joist, the OSB is pretty stable.


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Old 12-18-2006, 05:43 PM   #3
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I just did a 9x12 shed and all my seams are on rafters...no gap. So the contraction of the joist brings the OSB onto a collision course? So say the rafter shrinks to 1 7/16 from 1 9/16....so a 1/8 inch collision. But not until many years?

Last edited by pmaru77; 12-18-2006 at 06:21 PM.
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Old 12-18-2006, 10:33 PM   #4
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The reason for this 1/8" gap is to take into account the expansive properties of OSB. LEave a sheet out in the rain and you'll see what I mean.
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Old 12-18-2006, 11:21 PM   #5
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I had built a roof over our front porch using OSB and did not leave an expansion gap...what a mistake! Over time it was easy to see the bowing that occurred. We had the house reroofed this year by a roofing company with me replacing the the porch roof sheathing.

I wanted to do the work for a couple of reasons...the main one being having access to run some telephone and computer cables to other rooms in the house and to use 3/4 inch ply instead of 1/2 inch the roofing company wanted to use.

An expansion gap of 1/8 inch was used and the areas I felt were too tight I ran the skillsaw along the seam with the blade set at 3/4 inch. The roofing company and building inspector were both pleased with the gaping between the sheets.
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Old 01-31-2007, 11:46 AM   #6
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Use the clips.


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