Decking timber built-up members and the gap

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raydenl

99 posts

Master Geek

#281450 18-Feb-2021 15:27

Hey all

I'm currently building a deck, and using 90mm x 140mm bearers, constructed from 2x 45mm x 140mm SG8 H3.2 pieces of timber. I have followed the NZ building standards for creating built-up members https://www.buildmagazine.org.nz/index.php/articles/show/built-up-members-2. Oh yea, I also used No More Nails before nailing. But still there is a gap appearing between the members, and I am concerned the water that gets between them will accelerate the degradation of the timber. Wondering if I should silicone the gap, not sure how that would go on bare, wet, treated timber. Or is there another product? Or... am I just worrying about nothing??

Cheers

Fred99

13684 posts

Uber Geek
+1 received by user: 10018

#2659109 18-Feb-2021 16:03

I think you're probably worrying about nothing.

Greater then H3.2 treatment such as H4 is for ground (ie soil) or direct concrete contact (ie piles etc).

I wouldn't have used no more nails - that's probably set hard and you wouldn't be able to reduce the size of the gap now even if you tried.

The deck we built (engineer designed) has 2 x 190 x 45, they're not nailed together at all, but held together with 2 x 10mm coach bolts and washers spaced at IIRC 600mm centres.

wellygary

8810 posts

Uber Geek
+1 received by user: 5287

#2659119 18-Feb-2021 16:51

Its H3.2 so its pretty well protected already,

Its the same grade as fencing and most of those have plenty of gaps between rails and palings, but if you are worried do what everyone else does and slap paint all over it.....:)

debo

309 posts

Ultimate Geek
+1 received by user: 154

#2659170 18-Feb-2021 20:21

Buy Metalex Green and paint that on. Don't seal it up because that will trap water in.

Froglotion

208 posts

Master Geek
+1 received by user: 78

#2659277 18-Feb-2021 22:09

I wouldn't do anything with the timber, build it to the guides and live happily ever after. So long as the H3.2 isn't too close to the ground, it won't need glue / metalex treatment / paint. Metalex is good for putting on cut ends, to keep the treatment of the timber level up. But I certainly wouldn't paint it on the whole lot, it's potent stuff!