Jennifer wrote:

I recently installed a nice bathroom sink vanity that is constructed
with particle board. To protect the board and guard against
under-the-sink damage from leaks, mold, bathroom humidity, etc, I am
thinking of using (oil based) polyurethane on the interior, which is not
painted. Is this a good idea? Are there reasons why this should not be
done?

Thanks!





It should definitely be protected, and would have been best done before
you installed it. Particle
board will crumble if it becomes wet, including at seams in coverings
like formica. If you have a hard
floor, then caulking around the base is also a good idea - there will
invariably be spills on a bathroom
floor, at some point, and p.b. will bulge first when wet and then start
crumbling because the binder
dissolves. If there are joints at the bottom inside of the cabinet,
caulking there, also, would be a good
idea. I would prime and paint it, but at least two coats of something
should be applied.