Should You Seal a Cedar Birdhouse? (When I Do and When I Don’t)
To seal or not to seal. That was the question I asked myself after building my first cedar birdhouse.
The house was finished. The roof was on. The hole was drilled. Everything was ready to go except for one thing. I couldn't decide whether to put a finish on it or leave it alone.
The more I looked into it, the more I realized there wasn't one right answer.
For the houses I build, I keep things pretty simple. If I paint the outside, I seal the outside. If I leave the cedar natural, I usually don't do anything to it. Either way, I leave the inside unfinished. No paint, stain, or sealer. From what I've learned, it's better to leave the inside natural, so that's what I do.
If I'm painting one, I'll sand a few rough spots on the outside and smooth things out a little. Nothing fancy. Just enough to help the paint go on clean. Once the paint is dry, I usually brush on two thin coats of exterior spar urethane. Sometimes I'll add a third coat if I think it needs it. I'm not trying to make it shiny or waterproof it like a boat. I just want to give the painted outside a little protection from the weather.
Once everything is finished, I let the paint and sealer dry and cure completely before I put the birdhouse outside.
If I leave a house natural, I leave it completely alone. No sealer. No oil. No stain. That's one of the reasons I like working with cedar. It holds up pretty well outside without needing much help.
I've watched painted houses age well, and I've watched natural cedar weather on its own. Some turn gray faster than I expect. Some hold their color longer. After a while, I stopped trying to predict what each one was going to do.
That's probably why I don't worry much about leaving a natural house unfinished. Cedar seems to do what cedar has always done.
I just build the house and let the wood take it from there.
A note on what I found: When I was looking into this, Cornell Lab of Ornithology's NestWatch recommends leaving the inside of nest boxes unfinished and, if you paint one, applying paint only to the exterior.