Exterior Wood Door Finishes

For the record: did we mention that clear finishes on exterior doors do not last? March 9, 2008

I am looking for ideas concerning the finish best suited for exterior doors. These doors are raised panel red oak located at an entry to a local church. The doors and transoms are quite large and are exposed to weather without any protection. We originally used conversion varnish, and have since applied spar varnish once the original finish started to deteriorate. The spar varnish is now having the same problem as the original conversion.

Forum Responses
(Finishing Forum)
From contributor D:
The short answer is that all wood finishes fail in exterior situations. When they fail and how they recoat is what separates the men from the boys, so to speak.

First - there is no miracle finish that will endure for long in UV exposure. None. Epoxy systems are now getting lots of press, but have you ever tried recoating? Second - the boat method says coat with lots of glossy spar varnish, and strip and redo every 2 years. Not a pleasant thing to explain to your customer. Third - finish that fails in such a way as to allow recoating with a minimum of removal or problems.

We use Sikkens Door and Window. As it fails, it gets thin and faded. It is then time for a recoat. We now have a 10 year track record with Sikkens and see no reason to change. Biggest drawback by far is slow dry time - it will drive you nuts. But future recoats can occur on site, by mostly unskilled painters.

Anybody can make a wood door look like furniture, but no one can make it last if it is exposed. One large international maker/importer nearly went bankrupt with their 12 step catalyzed finish. Looked great, but failed dramatically and with great difficulty in removal.

From contributor J:
There is a 2-part acrylic polyurethane from Milesi spa from Italy. It costs about 3 hundred a gallon, but it is what you are looking for. I use it to finish exterior entry doors as well as other wood projects facing the south and on the great south bay of Long Island. Never once had a problem or complaint. Easy as lacquer to use, dries just as fast, and looks incredible. They say it has a 5 year life expectancy, but I have never heard a single complaint over 7 years of doing exterior. The only problem is there is no gloss (they sell gloss, but it is 50 sheen).

From contributor M:
I have at least 6 exterior coating failures to deal with this year. All at least 2 years old. I've used every product out there. I've had every rep to the job site, to my shop. Here's what they all told me. Coat heavily, all surfaces - every miter, every joint, every back - before you even put it together. And then, don't expect more than a year of blissful non-maintenance. Wherever water can get in, you will have finish failure.

Everything I've done is furniture quality. The 2k polys spray and look great. But so many of today's grand entry ways have so much trim and exposed surface area, you're asking for trouble. This post is directed to finishers. We are the tradesmen who will get the blame for the finish failure. Trust me. This is a very important subject. I lose sleep at night over customer and builder fury due to joint movement, finish failure, color fade, chipping, peeling. I no longer spray any exterior jobs. I also lose a lot of profit, because there are a lot of exterior jobs available. It shouldn't be like this.

From contributor R:
Conversion varnish is not an exterior finish. I hope you completely removed it before the spar varnish. I like Sikkens Cetol 1 and Cetol 23. I have recently been using a product from Canada on commercial jobs that seems to be working real well, but I don't have any real long term experience to share yet (Polyacril 99). It is a 2-part finish that builds well and dries fast. If these doors are exposed to direct sun and weather, an enamel or epoxy paint may be the only coating you could safely use. There is also the possibility of replacing the door with a fiberglass door that looks like wood.

From contributor A:
I've tried spar (marine) varnish, polyurethane, and heavy duty WB urethane, and they all fail after several years of strong UV exposure and/or high humidity. I've known folks who've used high tech finishes (2K urethanes, etc.), and they may last a little longer, but they fail too - and when they do, they're more of a pain to refinish. I've come to the conclusion that the best solution involves paint and not a transparent finish. When the millwork has to be finished with a transparent finish, I've found the best solution involves regular maintenance: stain and finish with a high quality varnish (spar or regular) or polyurethane initially. Clean and sand the door, etc. annually (in spring), and apply one thin, fresh coat of the original topcoat.

From contributor G:
In my 30 years experience in wood finishing - both spray and hand - no clear exterior coating has lasted more than three years before failing. The only exception has been a tung oil/varnish mix with high maintenance, like waxing twice a year plus a sanding and quick recoat every 5 years. My own neighborhood had a long tradition of faux painted woodgrain entry doors. They would usually last 10 years.