Is polyurethane only for stained wood, and not painted wood?

A. I've used polyurethane on both bare wood and on painted metal with good results. No inherent reason it wouldn't work on painted wood. First try the polyurethane in an inconspicuous spot to make sure it doesn't dissolve the existing paint. If it does dissolve the paint, you *may* be able to use several very light coats initially to seal the paint surface. In either case, prep the existing paint as you would for any other re-paint. For instance if the existing paint is glossy be sure to sand or etch it first, and as always, make sure it is clean. Do keep in mind though, that polyurethane is somewhat difficult to strip for that 'next' paint job.

A. I've never done anything like that myself, but I can offer an educated guess. Most likely it will NOT work, polyurethanes are mostly stains versus surface finishing. The polyurethane works by working it's way into the wood and then hardening, causing a good weather repellant coating.

It could work, but most likely not, it will just sit on top of the paint and won't really offer any added protection. I suggest stripping down the paint on there and use the polyurethane on the whole thing.

A. I personally would not coat white with most polyurethanes. The majority of the urethanes you come across are not UV stabilized...when exposed to UV rays(sunlight)they will yellow with age. This isn't very apparent when coating warm colored woods but it will make your white look pretty nasty. They do make special urethanes that you can mail order that are UV stable..but they are expensive..if my memory is correct I think I had to pay about $90 a gallon.

A. You can buy UV inhibited polyurethane, but it is not clear! It is for exterior work and is a sick honey color right out of the can.

A. Hi, Shelley. Based on the above, I'd say yes. We polyurethaned an outdoor bench for the very rough service of our sun-drenched deck on a salt water lagoon, and it lasted at least several years. I also see wood patio furniture for sale, advertised as finished with UV-resistant polyurethane. Sounds fine, good luck.

Regards,

A. Hi Aleta.

I'd be concerned about it getting too slippery when wet. Not recommending a particular brand, just a concept, but I feel you'll be okay with stain every 3-4 years, and something like Thompson's WaterSeal [affil links] every 2-3 years (better yet, every year if you're ambitious; it's transparent and if you run out of time partway through, it won't matter if you're trying for every year.)

Regards,