All Replies on How often does exterior polyurethane need reapplication?

  • Advertise with us
View JSThoreau's profile

How often does exterior polyurethane need reapplication?

by JSThoreau
posted 08-04-2016 02:21 PM

2 replies so far

View mahdee's profile


4291 posts in 2647 days

#1 posted 08-04-2016 03:20 PM

Hi Jacob,
I think it should hold up well as long as there are no sun exposure on it. I use the spar Urethane on the door on my shop which has direct exposure to the elements and it didn’t last for more than a year. I think your assumptions are accurate.


View JBrow's profile


1368 posts in 1799 days

#2 posted 08-04-2016 05:51 PM


A ceiling is a little different from the experience I can share regarding renewing Helmsman Spar varnish, but perhaps it can be helpful. We have a west facing covered patio. Setting on the patio is a coffee table and an end table both with a red oak tops (base is metal). When I finished the table tops I applied 5 coats of Helmsman Spar varnish on all six sides. This year, two years after being completed, I applied a renewal coat of the spar varnish. I did so only because the gloss sheen had become dull.

The table tops get far more weather than the ceiling of the patio cover, so I would expect the spar varnish to hold up a little better on the ceiling. Therefore a renewal of the ceiling I would think would be less often. I would be concerned that if not renewed often enough, the UV bouncing up to the ceiling could lead to cracking and peeling. A periodic renewal coat when the finish becomes dull therefore is probably a good idea. I would guess renewal would not be required more often than every 3 – 5 years, but annual inspection is probably better.

I would guess that the cracking and shrinking is due to only one side of the ceiling being finished. Had all six sides been coated with a sealer, the cracking and shrinking would probably have been less.

The dark moldy patches are a mystery to me. I maintain a red oak picket fence annually and notice what I think is mold in the wood. Bleach and soap does little to remove it. I have yet to figure out why it occurs on the sealed fence, how to prevent it, and how to remove it without deep sanding. My theory is that the sealers I have used are penetrating oils, thus leaving places where mold can get a foothold and then grow. If this is correct, then a film finish like a spar urethane should prevent its re-occurrence – but I really do not know.

Have your say...

You must be signed in to reply.

DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

Latest Projects | Latest Blog Entries | Latest Forum Topics