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Should I caulk my OSB3 expansion joints?
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Author:  Waka [ Fri Jul 06, 2018 7:46 pm ]
Post subject:  Should I caulk my OSB3 expansion joints?

Ok guys, so my first layer on my ceiling uses OSB3 tongue and groove boards 18mm thickness. I was planning on caulking the expansion gaps, but hesitated due to them... being expansion gaps.

I'm not expecting much expansion as the room will be heavily insulated and airconditioned.

If I don't caulk the joints then mass will be less along the joints. I'm doing 2 layers of plasterboard on top so I shouldn't have issues with the airtight seal though.

I'm leaning towards caulking them ( they'll still expand 25%ish of the original amount as the caulk is flexible, and I believe the OSB shouldn't have drastic temperature changes as it is beneath 100mm rockwool and will have 200mm below it.

What are your thoughts?

Author:  Waka [ Fri Jul 06, 2018 10:18 pm ]
Post subject:  Re: Should I caulk my OSB3 expansion joints?

Looking into it, I've come to the conclusion that I will caulk the t&g expansion joints. It seems that the expansion joints come into play mainly when the OSB takes on moisture, but as the OSB is a middle leaf inside the water-tight building evelope, is OSB3 (water resistant), my room will be humidity controlled, and the caulking is flexible, I don't forsee this becoming a problem.

Author:  Soundman2020 [ Fri Jul 06, 2018 11:42 pm ]
Post subject:  Re: Should I caulk my OSB3 expansion joints?

Yes, caulk it. Always caulk any gaps, anywhere.

Quote:
If I don't caulk the joints then mass will be less along the joints.
Right. And there won't be a good seal...

Quote:
I'm doing 2 layers of plasterboard on top so I shouldn't have issues with the airtight seal though.
Ummm..... You have to seal EACH layer INDIVIDUALLY. Each layer by itself must be fully sealed, if you want maximum isolation.

Quote:
they'll still expand 25%ish of the original amount as the caulk is flexible,
You should be looking for a better caulk, then! Most good caulks can handle a lot more than 25%.

Quote:
I've come to the conclusion that I will caulk the t&g expansion joints.
:thu:


- Stuart -

Author:  Waka [ Sat Jul 07, 2018 1:51 am ]
Post subject:  Re: Should I caulk my OSB3 expansion joints?

Hi Stuart, thought you'd say that! Obviously sealing every layer is ideal as there is more redundancy incase of sealant failure, Bmbut I also want the sheathing not to buckle ;), that's why I considered before caulking it.

My caulk is highly rated Everflex AC50

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