# tarpaper or tyvec under cedar board and batten



## joecaption (Nov 30, 2011)

Tyvek would be my first choice.
Faster since you can cover a whole wall with one sheet, less likely to tear when installing, less seams.


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## rustyjames (Jul 20, 2008)

Do your homework before you decide on fastening it directly to Tyvek. I've read about it disintagrating under cedar.


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## bill32439 (Jan 25, 2014)

Thanks for the info and ideas. I'll do some checking around.


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## Windows on Wash (Aug 30, 2011)

Given Florida rain totals, I would like to see some sort of rainscreen if possible.

FYI...Tyvek is not a vapor barrier. Its whats considered a WRB.


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## Gary in WA (Mar 11, 2009)

http://www.diychatroom.com/f9/drainable-house-wrap-194692/

Gary


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## Gary in WA (Mar 11, 2009)

Got confused.... don't get old. 

The tannins in cedar siding will cause Tyvek to lose water resistant ability. Back prime the cedar, use builders felt paper instead;http://www.greenhomebuilding.com/pdf/RainScreen.pdf

Unprimed cedar wicks water causing face swelling, paint blistering- no so much with boards; http://www.energyoutwest.org/eow_lib...gas_Damage.pdf

Gary


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## ben's plumbing (Oct 6, 2011)

tarpaper....:thumbup::thumbup::thumbsup: ben sr


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## woodworkbykirk (Sep 25, 2011)

another one for tar paper if your going to be installing the cedar directly over the paper, if your doing a rainscreen you can use tyvek as the cedar wont come in direct contact with the paper


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## roofnron (Dec 7, 2011)

My vote would be 30lb felt but check your manufacturer specs. 

http://www.realcedar.com/siding/preparation/dupont-tyvek-drainwrap/

"..., the Western Red Cedar Lumber Association recommends DuPont™ Tyvek® DrainWrap™ for installing Western Red Cedar siding."


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## Gary in WA (Mar 11, 2009)

Any drainage mat type product (rainscreen) over WRB is better than a drainable HW product in this installation. You need that drainage space to encourage back-drying. Felt wicks any water from behind it to dry outward, and helps seal the fastener holes, plastic WRBs don't, like plain Tyvek- with/without a rainscreen. http://bct.eco.umass.edu/publicatio...-felt-paper-and-weather-penetration-barriers/

For the South, a 15perm WRB is ideal, felt is variable 5-25perms; 
http://www.jameshardie.com/pdf/hardiewrap-consumer.pdf Tyvek is 58perms....

Two layers of felt is better; 30% fasteners leak vs. 8% leakage;http://www.google.com/url?sa=t&sour...sg=AFQjCNFUzTvRGq1GWFv4H951L4-bkv-Xgg&cad=rja

Problem with a drainable HW is the board siding or lap siding is pressed tightly against the sheathing at install; effectively stopping all back drying, (actually same with felt,) though as the boards dry/wet with the changing seasons= liquid water/RH; they expand/contract to promote air spaces for drying. At install, be sure to fasten so each board can move (don't nail through another under-lying board- eg. batten through board); http://www.realcedar.com/siding/installation/board-batten/

We could discuss minimum depth for a rainscreen or vented vs. ventilated rainscreen but sounds like they don't apply here.... and even different tests for the WRB, to get the best. How are you applying the WRB for water-tightness? Any ideas on the flashing you will be using at windows/doors, or questions we can answer?

Gary


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## Knucklez (Oct 21, 2007)

> Do your homework before you decide on fastening it directly to Tyvek.


you are not supposed to install board direct to house siding. must be 1/2" gap to dry the boards. if your house has exterior rigid foam insulation as well, then you need 1" gap! this comes from Cap Cod, huge manufacturer of board & batten (i installed on my own house several years ago).

http://www.diychatroom.com/f19/board-batten-wood-siding-20032/


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