Hemlock – Open Gap Rain Screen Siding
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My use of eastern hemlock as a siding material has been generating interest. Hemlock is a common wood in Vermont but doesn’t get used a lot except in barns and outbuildings and sometimes for timber frames. My summer job during high school involved working in a small sawmill. We sometimes...
My use of eastern hemlock as a siding material has been generating interest. Hemlock is a common wood in Vermont but doesn’t get used a lot except in barns and outbuildings and sometimes for timber frames. My summer job during high school involved working in a small sawmill. We sometimes cut hemlock and I found the wood beautiful, but heavy. One summer, we cut some hemlock for a bridge. Fast forward um… lots of years and I ordered a bunch of hemlock for framing and decking when I built my barn. I learned a bit about how to work with hemlock, how it ages and weathers and I started thinking about how I could use it in my own work. I try to source materials as locally as possible and design within local builder’s abilities and interests – which is easy to do here where builders get together monthly to discuss building science related issues
In rural New England, buildings are often sided with pine siding in a vertical shiplap form – and often unfinished. It tends to develop a black mold that is relatively harmless but can be ugly. I found that hemlock is more resistant to this mold. It’s also harder and more rot resistant. It is nowhere near as rot resistant as cedar, a more common siding material however.
It occurred to me that I could use narrow hemlock boards from local mills to create a very elegant (I hoped) rainscreen siding detail. It would use local and relatively inexpensive materials, it wouldn’t need paint or stain, installation could be simpler and faster if I got the details right, and if I installed it horizontally, the lowest courses could easily be replaced if the siding degraded due to splashback and snow banks. The damaged siding would not present a disposal concern – just toss it in the bushes and it becomes habitat for red backed salamanders.
I was lucky to have a client with a taste for modernism allow me to try my ideas out on his home. The results were rather spectacular and gave me a sense of the potential. Now I am doing my second project with hemlock siding. The builders for this project (Webster Construction of Marlboro, Vermont) are quite familiar with good building science and modern products and methods. They saw the potential and were happy to give it a try plus they were able to improve my detailing in several ways which I can then incorporate into drawings and specifications for the next time around.
The hemlock turns silvery gray within a year. The narrow boards create a woven, fabric-like aesthetic.
The hemlock is installed “green” with deck screws. This siding is all 1×3 so gaps will be quite small as the wood dries. Fiberglass bugscreen is installed directly behind the siding. strapping can be regular 1×3 strapping although coravent makes an excellent product for this purpose and should at least be used on any strapping set horizontally such as over and under windows.
This is the corner trim detail the builder came up with and I really like. One side runs long and is cut after installation. The other side is held back for a crisp reveal – very architecty! Of note: the deck is white oak (local) and the post is European Larch which is from a harvest of a Vermont tree farm. European larch is used in Europe as a durable siding material that needs no treatment.
detailing around windows is super simple. On the first house I used metal panels (installed by the roofer) to accentuate the windows and wrap corners. Here it is about as simple as it gets.