I'm building a large outdoor living space in the pacific northwest (Vancouver, Canada) with rafters, purlins, beams, and posts all douglas fir. It will all be covered with transparent polycarbonate roofing (Suntuf). The roofing will block most UV light and all the rain except some occasional horizontal/windy rain.
I love the dark red color doug fir turns indoors when totally untreated. What will happen in 5-20 years if I leave my outdoor fir untreated (no paint/stain/oil/anything)? Is ambient humidity in a wet climate enough to rot the fir? Or make it go grey or black?
Thanks so much for your experience!
Best Answer
Since it will be covered it won’t rot away but it will turn gray. I also live in the Pacific Northwest south of you , condensation is the biggest issue I see and occasional condensation is not a problem. My riding arena 120’ with poly the entire length for light it is 30 + years old with no issues but is 22’ up so the color is far enough away we don’t notice the gray. I did paint the back porch because I thought the bare grey wood looked bad after a few years. So since it will be covered it won’t rot away but will turn gray.