Coating Choices for Exterior Wood Doors

Here's another discussion sorting through the options for wood door finishes that have to face exterior exposures. March 28, 2012

I've recently had a front door made for my house and am in the process of having it "sealed/finished" to protect it from the elements. After much searching with local shops, I'm leaning towards having the door coated/sprayed at an automotive body shop with an automotive lacquer.

My question is that if I have this procedure done can I maintain the protective coating over the years without removing the door to do so? That is to say is there a maintenance coat that would not require spraying (brushing or rolling that would work over top of the automotive lacquer)? The door is large and heavy and removing it yearly or bi-yearly would be a pain. The door consists of a Timberstrand material with a walnut veneer overlay. Any help would be much appreciated.

I've heard that Sikkens Cetol 1 instead of the automotive lacquer would do the trick, however the Sikkens Tech wouldn't commit to their product working on the door for protection against the elements.

Forum Responses
(Finishing Forum)
From contributor H:
There are numerous issues with spraying on an automotive finish. First off, you are not going to use a lacquer - most automotive paints are either a cat urethane or a WB urethane or acrylic (not available unless you have CNC spray equipment).

Second, wood has properties that sheet metal does not, like moisture transfer (in or out of the wood).

Third, auto paint only comes in high gloss. If you abrade it with steel wool to knock the gloss down you increase the surface area of the finish and will destroy its durability. Cetol "Door and Window" is not a bad finish, durability is fair, surface quality is poor, but is very re-coatable. I have it on my garage door and exterior trim work including eaves and I get about one year in the Northern California sun. What you want is an Isocyanate or exterior 2-pak urethane. It needs to be sprayed on, but can be done in the field. We have around 700 large units that we have finished and maintain. The worst exposure that I have gets re-coated every few years, normal re-coat is three to five years.

From contributor O:
I have made custom exterior doors for 40 years as a professional. Here is my take: All exterior wood finishes fail in time. An automotive finish will fail faster due to the movement of wood being about ten to twenty times greater than that of metal/plastic. What makes a difference is how exterior fail as well as how quickly they fail.

Bullet proof catalyzed, epoxy and other two parts will still fail, and when they do they must be completely removed - an expensive and time consuming proposition. So what does the world do? The Europeans prize their wood doors, and Sikkens developed a finish for that use. It also fails but does so in a way that allows easy maintenance. The Sikkens, as it ages, starts to look physically worn and thin. This is your clue to add another top coat. Clean the door and coat it with Sikkens and a foam brush and wait for it to dry. Depending upon exposure, you are good for another two to twenty years.

The other option is wood boat bright work and use Spar varnish, but realize boat coatings are made to be removed and renewed periodically so the same will happen to your door. Of course, the best designs have protected entries so that doors (and guests) do not get exposed to UV and rain in most circumstances. This is the best strategy, and the one where we have a five year warranty that kicks in. I'm curious, what does your door maker suggest?

From the original questioner:
Just as a point of clarification I do not intend to do the automotive lacquering myself. An acquaintance of mine who owns a body shop was prepared to spray/finish the door, so the need for me to personally acquire any product is not necessary. However, having said that, it would appear to me that the Sikkens product would be the way to go.

The company that contracted the door for me (I believe they subbed this job out of shop) suggests that I use a product from WL Campbell called Euro X which from what I can determine is relatively expensive and difficult to use (at least that's what my wood finisher says). I would have them (the people that I contracted the door through) finish the door but that would require re-crating and shipping the door back to them and doing the same after they finish to get the door back to me which would be costly and very time consuming (we're in different cities, many miles apart).

From contributor H:
I do not know where your home is but you should be able to find a finisher that will not go to the nearest box store for a can of poly. Stay away from the WB's they do not hold their color well outside even if they maintain their film integrity. Real spar varnishes are long oil materials that take forever to dry to dust and are not designed to have a flawless finish. Cetol Door and Window is alright but with the fused iron as the U.V. filter they do not have a furniture quality look and they take forever to dry to dust. The iso or 2-pac sprays on like a lac and is re-sandable the next day and if you seal twice (wet on wet), sand, and Scotchbrite out and two final coats you are set for three to five years. Re-coats are easy and you have a sprayed finish quality that is fitting of the entryway. Call a local door shop and find out who they use.

From contributor A:
I have used the MLC Euro product to which you refer and also the Sikkens Cetol. The MLC product is not hard to spray. There are different catalysts, and time limits, both pot life and when the cat is opened to air, but nothing you can't handle being organized and studied going into the project.

That being said, I have steered away from that product because it didn't hold up, and as stated, we're then back to stripping and re-coating. If you think spraying on-site is a pain, try stripping. Yes, the first day off of the gun the product looks much better, but that isn't long lasting and soon that's all forgotten when the topic of conversation turns from the great looking door to how to we refinish the beast.

From contributor J:
If you can spray Sikkens indoors, and wait a week before installing, it's an ok product. In the field, Sikkens just takes too long to dry. It does not really brush out all that well. I believe Akzo Nobel has had to re-formulate the finish (VOC compliant) so much that it no longer is what it used to be.

Currently, for field work I use what to what most boat owners use: Epifanes - gloss for the first two or three coats, satin for the finish coat. If you take the time the finish will last over four years. I do work in Michigan and the doors which have Epifanes on them have lasted more than the doors I have coated with Sikkens. I have done a few with a FUHR waterborne and it sprayed beautifully on site!

From the original questioner:
It would appear that I'll probably go with the Sikkens Cetol 1 and after speaking with my spray/finisher guy I'll roll it on instead of him spraying. I'll do so while laying the door flat giving it a few good coats and letting it dry for a couple of days before turning it over and repeating the process on the other side. I am also going to speak with a fellow I know that owns the Benjamin Moore store to see if he can recommend a product to use.

Like I said my preference is to have it sprayed but my problem is finding the product to spray that can then be maintained down the road through a brush or roller application without re-stripping and refinishing. Iím still open to suggestions and thanks for all your help and opinions so far. Everyone that has responded has given me good information and this will assist me in making a decision.

From contributor Y:
I just recently came across "San Marcos" paints, and they have a clear that has UV protection for exterior use and produces a furniture finish, brush applied, and is safe for the environment.

From contributor N:
My vote is for spar varnish but all exterior clear finishes will need constant maintenance to continue looking good. How often you need to refinish will depend on the exposure of the door.

From the original questioner:
I also thought that a spar varnish would work but as I said, I have very little knowledge in this area (finishing wood). The door has minimal exposure to UV because it is on the North side of the house with 3' eave over. However because I live in a Northern area we do have snow in the winter months and rain in the summer (dry heat) generally.

My concern is to protect it from those two elements which would be mainly moisture. I have no problem with the maintenance as long as it doesn't require me to remove the door to do it. Also I would prefer not to have to spray on the maintenance coats or to strip the door to apply the maintenance coatings. Is this possible with a spar varnish?

From contributor N:
Spar varnish does not spray all that well and is best applied by brush. If you recoat before the finish fails it would not have to be striped every time. Eventually the finish will have to be striped when the coating becomes too thick. Varnish strips fairly easy compared to 2k poly.

In my opinion spar varnish will give you the best clear coat protection against water. The best protection for an exterior door is opaque paint all clear finishes will need constant maintenance. A storm door would also be a big help in protecting the door form the elements.

From the original questioner:
It sounds to me like I'll have to give the spar varnish a go. I'll check locally for a supplier. I believe that Benjamin Moore has a spar varnish and if what you say is true, this sounds like the product for me.