Unfinished spruce clapboards over rainscreen system

Kyle Arve| Posted inGeneral QuestionsonDecember 27, 2019 03:33pm

Hi, looking for thoughts and opinions on using unfinished spruce clapboards over a rain screen system. Durability? Weathering? Mildew?

Will sealing with a waterproofer extend the life of siding or is air gap enough to do that?

Furthermore, does anyone have experience with Vermont Natural Coatings penetrating waterproofer with juniper on exterior siding?

Thanks a lot.

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Malcolm Taylor|Dec 27, 2019 07:22pm|#4

I'll let the New England contingent weigh -in. Out here in the PNW it wouldn't be an option, but perhaps your climate is more forgiving.

Keith Gustafson|Dec 27, 2019 05:58pm|#2

unfinished spruce is probably not the best bet for longevity. I would think they are primarily intended to be painted, but I could be wrong.

VG cedar would last forever........
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Michael Maines|Dec 28, 2019 09:40am|#5

I've installed spruce clapboards, from the Ward clapboard mill. Spruce has essentially no rot resistance without a finish. Even if installed on a rain screen they won't last long--maybe ten years before they start failing. I use spruce leftover framing lumber for outdoor projects regularly, and even above grade where the wood can dry readily it does not last long. That's fine for my projects, which are intended to be temporary, but you want siding to last more than a few years.

Clear "waterproofing" sealants don't last long. You would either need to recoat regularly or use a finish with a pigment that protects the wood from UV exposure.