Guidance Request for Polyurethane Application

[Glen Blanchard]

12 months ago we had a painter re-stain the outside of our exterior doors and apply some (we presume) polyurethane. At the time the work was done he recommended re-applying the finish annually. This year my wife and I thought we would attempt this task and save a few bucks. My experience with polyurethane is pretty limited, so I have some questions.


Although we believe that the product he used last year was polyurethane, we don't know that to be fact. Would it be problematic to apply the poly if some other finish was used last year?
What surface preparation (if any) is needed prior to the new application? a light sanding? if so, with what grit?
Should I thin the poly? If so, to what extent?
Any pearls or words of wisdom? Is this a task I can take on myself or should it be relegated to a professional?

[Steve Schoene]

Let us hope that he didn't apply polyurethane, since that in most cases that varnish is not very durable in sunlight. Can't you ask him what finish he applied? Has the door show signs of weathering badly? Is the varnish lifting or showing lighter "yellow" patches.

In any case, it won't really matter what was originally applied since it has had sufficient time to cure fully. Preparation would be a light, but thorough sanding with 320 grit sand paper. If there is pealing or lifting or such defects however you will need to strip off the old finish and start over.

For the new top coat, I would select a marine spar varnish. You will only find such a material at a boating supply store. Acceptable brands are Interlux Schooner, Epifanes Gloss, and Pettit Captain's. Products that sound link marine spar varnish that you find in ordinary paint stores or the big box stores IS NOT.

Get a quality brush, about 2" wide, of natural bristle. It should cost as much over $15 as you can afford. You will want to thin the varnish, typically it will take about 10% thinner, a bit more if you choose the Epifanes. It will be much easier if you remove the door from its frame so you can varnish it horizontally. You may want to find a sample to practice so you are comfortable with the method.

[Art Mann]

I would like to re-emphasize what Steve has said to save you from something like my own bad experience. Do not buy so called spar varnish like Minwax Spar Varnish and similar products sold in the big box stores. The material will crack, peel and turn yellow, even in indirect sunlight like under a North facing porch.

[Ken Fitzgerald]

Glen,

2 years ago I used Epifanes brand on a white oak swing I made for my wife. I found it easy to use.

[Glen Blanchard]

Perhaps it was not poly that he used. That was merely a guess on my part. I don't see cracking or yellowing from what he did last year, so now I am under the impression that he used something other than polyurethane. Lots of pertinent information here that I will put to good use. I think I'll get some Epifanes and test a section of one of the doors after a light sanding and see how it looks. Thanks guys!

[John TenEyck]

Perhaps it was not poly that he used. That was merely a guess on my part. I don't see cracking or yellowing from what he did last year, so now I am under the impression that he used something other than polyurethane. Lots of pertinent information here that I will put to good use. I think I'll get some Epifanes and test a section of one of the doors after a light sanding and see how it looks. Thanks guys!

Why not hire the pro again - and find out exactly what he uses. Next year, you can do it yourself knowing what products to use.

John

[Ken Fitzgerald]

I would find out what the Pro used before putting anything over it even Epifanes. Some finishes don't like to stick to other finishes and you might find yourself redoing it again soon.

I like John's recommendation.