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Rainscreen for vertical cedar siding?

Hi all,

My builder is concerned about all the trim around my remodel due to my wish for 4" tongue-and-groove western red cedar (WRC) vertical siding. I will be mixing things up with about 1/3 of the outside coverage with WRC shingles so the product depth is not an issue.

The old (beautiful) fir T*G 1x8 sheathing is still intact but now covered with Henry Blueskin 100 as a WRB. I was planning on using Home Slicker over this, and then the vertical siding and shingles for the final. My carpenter is worried that the 3/4" T&G cedar plus the 1/4" or 6mm Home Slicker will make all the trim non-standard. He would like to use full 1" or (5/4 PVC trim) and cut a 1/4" channel to tuck the vertical siding in to prevent water. I live on the ocean (Newburyport, MA) and wind-driven rain is always happening. Thus he does not want the full 1/4" Home Slicker.

My question is can I step down to Hyrdogap (1mm) or another thinner rainscreen? They seem to think this will work over the Blueskin. Note the T&G cedar is really 5/8" and not 3/4" but still, the combo pushes about 7/8", which make the 5/4 trim almost impossible without shimming out all the windows and trim to accommodate.

Thoughts on another rainscreen option?



Asked by david flinn
Posted Jan 12, 2018 10:00 PM ET
Edited Jan 13, 2018 7:14 AM ET


6 Answers

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When you add a rainscreen gap, you end up with siding that proud of the old trim. The right way to proceed is to remove the existing window trim, flash properly, add shims or jamb extensions, and then either add new trim (casing) or reinstall the old trim.

You can't get the benefit of a rainscreen gap without facing reality: the plane of your new siding will be proud of the old plane.

Answered by Martin Holladay
Posted Jan 13, 2018 7:12 AM ET


Luckily all the old trim has been removed so I have a clean plane to work with. You are indicating to me that the only way to have a true rainscreen is to shim all my windows and trim. Any thoughts on types of rainscreen options that would be about 1/8" in width so I don't need to install shims?

Answered by david flinn
Posted Jan 13, 2018 9:57 AM ET


You can certainly install one of the wrinkled or bumpy housewraps (like Hydrogap or one of its cousins) if you want. These products don't really provide any ventilation drying, and their ability to allow drainage is open to question. But these products are probably better than no gap at all.

For more information on wrinkled or bumpy housewraps, see All About Rainscreens.

Answered by Martin Holladay
Posted Jan 14, 2018 7:51 AM ET


we typically use 3/4" strapping for our rainscreen, but on one occasion when we needed to fur out new siding over 1/2" plywwod to the plane of the old sheathing, we used wood plaster lath. It's about 3/16", comes in 4' pieces and is pretty inexpensive.

Answered by Bob Irving
Posted Jan 14, 2018 1:15 PM ET



Thanks for the kick to re-read the great article about Rainscreens. I found that Keene Driwall comes in a 1/8" width option so I'm going to look into that. Another option is the use of 6/4 trim instead of 5/4, albeit the cost is higher. Thanks!

Answered by david flinn
Posted Jan 15, 2018 11:59 AM ET


Masonry Technology Inc also offers a 1/8" rainscreen that is less susceptible to compression & "sponginess" during installation than some of the entangled filament products. https://www.mtidry.com/gravity-cavity

Answered by Tyler LeClear Vachta
Posted Jan 15, 2018 12:32 PM ET

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