Do they attract owls? I've been researching them a little bit....just wondering if they are worth the work (if built) or expense (if bought). Thanks!
What do you have in mind? What kind of owls? Owls are pretty social here (big white faced ones). They like a clear path to swoop in and out. Most folks around here just have holes and a pirch in the gable of the barn with a box inside. I've seen boxes in one form or another on top of poles or roofs also. Another common companion is Kestrel falcons. They like the gable holes with just a shelf inside.
These people would probably know.
Since owl boxes are essentially bird houses I doubt you will have much of a problem, assuming you have the right kind of owls about.
Owl boxes do work if they're built to the correct size with the right size entrance hole and hung at the right height. Screech owl boxes can be made from one 1' x 8' board. Do a search to find the proper specs. for the type of owl you're looking to attract to the box. That will give you an idea of the amount of wood you'll need. Good luck.