What is a Rain Screen?

August 02, 2020

By: Lee LeFever

I write books and run a company called Common Craft. I recently moved from Seattle to a rural island. Here, I write about online business, book publishing, modern home construction, and occasionally, dumb jokes.

Today our house is sporting an exterior look that reminds me of dazzle camouflage, which was used in WW1 (and to a smaller extend in WWII) to it difficult to estimate the range of other ships.

We’re not hoping to fool the enemy, but mother nature. The stripes on our house are there to hold the siding away from the house in what is called a “rain screen”. Here’s the big idea:

Moisture is the enemy when it comes to house exteriors. If it gets trapped and can’t evaporate, it can start to rot wood and other materials. Houses usually have a couple of layers that serve as moisture barriers, like home wrapping (the black material above) and siding.

From what I’ve heard, it’s nearly impossible to prevent moisture from getting behind siding. Usually, it’s not a problem, but some siding does best when water can evaporate or drain quickly. That’s why a rain screen is used. It holds the siding about half an inch off the home wrap so that moisture can easily drain.

The stripes in the photo above are wooden boards that have been put in place to hold the wooden siding we’ll use. You can see that the walls alternate in terms of pattern. This is because the orientation of the siding will also alternate from vertical to horizontal.

It took me a while to realize why the middle section has diagonal stripes. This section will have vertical siding that could be applied on horizontal boards. Because the goal is drainage, the underlying boards must be diagonal to help with drainage.

The siding we’ll use is called Yaki Sugi and is cypress that has been charred on one side. This sort of rain screen was recommended by the manufacturer because the cypress does best when it can dry quickly.

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