What code covers rainscreens/drainscreens?
I’m currently remodeling in California and have hit an issue with the exterior siding. I would like a gap between the sheathing and the siding to allow for drainage and evaporation, but the building department sees it as something that needs fireblocking.
I’ve searched this site and come across this blog article, but the closest I can find is this article
https://www.greenbuildingadvisor.com/blogs/dept/energy-solutions/drainage-exterior-walls
where Alex Wilson, the author, states that he feels rainscreens should be added to the code. I take it they are not mentioned, and have searched for rainscreen or drainage plane with no luck. Can anyone offer some advice or hints on where to look? Thanks!
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Scott,
Your question has been addressed by Paul Fisette. There are no definitive answers to the issue, unfortunately. See an earlier discussion here at GBA:
https://www.greenbuildingadvisor.com/community/forum/energy-efficiency-and-durability/14545/fire-code-concerns-rigid-foam-panels
Paul Fisette's article on rainscreens and codes is here:
http://bct.nrc.umass.edu/index.php/publications/by-title/insulating-on-the-outside/
Rainscreens are code in British Columbia and judging by the FHB discussion forum also in Nova Scotia now.
Here is a reference guide that I tracked down that I first came across on the FHB discussion forum with drawings that show the BC rainscreen code requirements.
http://www.nationalhomewarranty.com/NewPDF/ACCEPTED_RAINSCREEN%20DETAILS-4_July-2007.pdf
Hope this helps. BTW, BC gets lots of rain, but they also had quite a fire problem this past summer. I don't quite know how you balance concern about forest fires and rain. That said in BC it is far more likely to rain, and lots!
Andrew
If you live in an area in which the risk of wildfire is greater than the risk of water intrusion from high climatic rainfall, then the building department is correct in not allowing a vented rain screen without fire stopping. The fire stopping reduces, but does not eliminate, the advantages of a rainscreen. You still get the capillary break and some evaporative potential but without the convective drying of an open cavity.
If you're not in a high rainfall area, then a well-detailed weatherbarrier (housewrap), carefully-integrated flashings, and back-primed and end-grain sealed siding will do fine.