Strapping material for rainscreen…plywood fir or spruce?

unclejemima | Posted in General Questions on March 16, 2015 04:24am

I’m ready to put the strapping on-top of my WRB, only I’m not sure what the best choice is.

I want a 3/8″ gap, so cutting plywood strips is my only option (there is NO composite furring strips available in town…I called everywhere!)

I’ve got the option of 3/8 spruce with exterior glue, or 3/8 fur with exterior glue.

Does either have a lower tannin content that may deteriorate the WRB? Do I even have to worry about that? Should I back prime the strapping to avoid this?

I’m going to put cement board over the strapping then stone.

Thanks!

Answer

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Replies

brp_nh | Mar 16, 2015 07:57pm | #1
Cor-A-Vent Sturdi-Strips (3/8" deep) are available from ABC Supply Co. if you can't buy from a local supplier. Their website doesn't look good, but they are legit:
https://abccatalog.com/view_product.asp?idproduct=2147801112

We used these with the SV-3 product for a vented rain screen on our house.
Expert Member

MALCOLM TAYLOR | Mar 16, 2015 08:52pm | #2
Mark, As far as I know Tyvek was the only WRB which had problems with deterioration due to cedar tannins, and they have since reformulated their product to address this.
GBA Editor

Martin Holladay | Mar 17, 2015 04:12am | #3
Mark,
Either spruce or fir will work fine. But I wouldn't use the fur if I were you.
mtr7982 | Mar 17, 2015 11:07am | #4
Martin,

The Native Americans, the original fur rainscreen , I believe they turned the fur in which would've prevented thermal bridging to the tee pee support poles. Hmmm you have my wheels turning.
unclejemima | Mar 17, 2015 12:06pm | #5
Thanks guys :-)

Brian, thanks for the link. I'm in Canada so the weak CAD, shipping and Duties would kill me :-(

Malcom. Good to know. I won't worry then.

Martin, I'll use the fir. Its difficult to find exterior glue rated 3/8" plywood, but I did find the exterior rated glue and fir for a reasonable price. 99% are interior glue and usually spruce.

Mr Miller...interesting reply :-)

Thanks all!
GBA Editor

Andy Engel | Mar 26, 2015 03:30pm | #6
I used mason's lath. I suspect it was poplar, but it's cheap and 3/8 in. thick.