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kfreesea
cedar shakes cupping

In late spring, I had 2 sides of my house stripped and new cedar shakes put up over new Tyvek (note: a 3rd side was replaced in 2005 and the front has a different product). I then had Rhinoshield paint applied a few weeks later. Rhinoshield was applied over an oil based primer.
After today's tropical storm we were surveying the house and grounds. I found that on the 2 sides where new shingles were applied, 10-15% of those shingles are noticeably cupping. I don't know if this was due to the quality of the shingles, the install of the shingles or the Rhinoshield. The 3rd side does appear to have been affected.
Any advice?
Thank you!

jkirk
Re: cedar shakes cupping

first question were the shingles installed directly on top of teh tyvek, reason i ask is that this is wrong the oils in the cedar will destroy the water proofing ability of the tyvek. its ok to use tyvek but there must be either cedar breather or privacy lattice installed on top of the tyvek first so to create a air space and to keep the cedar from being in contact with the tyvek

as for teh shingles cupping its caused by irregular drying of them, the wood is drying faster on the face than on the back plus the installer nailed too high on them. if you need to drive some finish nails to draw them back down

kfreesea
Re: cedar shakes cupping

The shingles are drying out and are now mostly flat again. I checked and he did install the shingles directly onto the tyvek. Should I make an issue of this with the installer? He is the same person who did the first side back in 2005, and did an excellent job. These 2 recent sides just don't look as good. Will they last?

jkirk
Re: cedar shakes cupping

the cedar will last a bit but with the cedar directly on the tyvek... the tyvek wont last, if the water gets behind the cedar you will have leaks.. make sure you make the contractor aware of this, he can use tar paper but not tarpaper.. if hes gets ignorant about it he needs to hang up the tool belt . he'd be fired off my site instantly and get blacklisted. siding and weatherproofing are a big deal, you cant mess around with it

Sombreuil_mongrel
Re: cedar shakes cupping

I'm gonna guess it's partly due to the fact that the undersides of the shakes are not painted, therefore in wind-driven rains they get wet while the outside sealed for now with some superpaint remain dry. This could be avoided by ordering the shingles pre-dipped in stain, and could have been made less troublesome by laying them over a mesh rainscreen product. At this point there's nothing to be done but get used to the post-deluge warping.
Casey

Gizmo
Re: cedar shakes cupping
jkirk wrote:

first question were the shingles installed directly on top of teh tyvek, reason i ask is that this is wrong the oils in the cedar will destroy the water proofing ability of the tyvek.

JK,,,,,

FAQ...Is DuPont™ Tyvek® a vapor barrier?

No, DuPont™ Tyvek® is not a vapor barrier. It is breathable, allowing moisture vapor to pass through it.

canuk
Re: cedar shakes cupping

Gizmo -- there's a differnce between water vapour and liquid water.
House wrap doesn't allow liquid water to penetrate yet allows water vapour to pass through --- that's why it's considered an exterior weather barrier.

Gizmo
Re: cedar shakes cupping

Wood Siding
DuPont™ Tyvek® weather barriers and wood siding shall be installed according to
manufacturer’s instructions, industry standards and applicable codes. As recommended
by the Western Red Cedar Lumber Association and U. S. Forest Product Laboratory,
wood siding should be primed on all six sides before installation. In high exposure
installations, enhanced drainage and water management may be provided by using
DuPont™ Tyvek® CommercialWrap® D or by creating rainscreen cladding with a larger
airspace behind the siding using furring strips.

jkirk
Re: cedar shakes cupping

dupont makes standard tyvek, and they make a version specific to wood siding which has the rain screen built into it. but its well documented that cedar should not be in direct contact with tyvek for the reason i stated. plus i have seen the results first hand

unless there is a difference in the product sold in the states

Gizmo
Re: cedar shakes cupping

I looked for any product/document/warnings from Tyvek, All I could find was DuPont™ Tyvek® weather barriers and wood siding shall be installed according to
manufacturer’s instructions, industry standards and applicable codes. As recommended
by the Western Red Cedar Lumber Association and U. S. Forest Product Laboratory

http://www.wrcla.org/pdf/WRCLA_Installing_Siding.pdf

Does the so called break down of the Tyvek have to do with the oils or Tanic Acid in the cedar ?

jkirk
Re: cedar shakes cupping

correct it is the oil tannins that do it. weve seen it here a few times then around 2005 the canadian code switched to it being mandatory for all wood siding to have a rain screen installed

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