Polyurethane: How Much Do You Need & How Long Will It Last? 12 months – The length of time a poly should be usable after you open the can.

Will polyurethane last outdoors?

Polyurethane is the most durable of clear exterior finishes. … Polyurethane can be used successfully outdoors if it has the proper ingredients. Look for a finish that has additives for ultraviolet protection. The label should say for exterior use so the dried finish will flex with the expanding and contracting wood.

Can you use polyurethane on outdoor wood?

Yes, you can use water based polyurethane outside for any outdoor furniture, decks or floors. However, ensure the water based polyurethane can or label has the right ingredients. It MUST contain additives for UV protection for it to be used outside. Besides, it should be labeled “for exterior use” to avoid chipping.