I live in a old (1936) house.
The front door (original)is thick wood with an arched top. I have sanded it down several times and re-finished it over the years. the last time I used a marine varnish over the dark wood Finnish. It lasted a few years and like other finishes it began to fade were the sun hits it.
There was a storm door (metal clad)that also faded. I like the front door with out the storm door.

Whats a good dark wood finish process for wood exposed to the elements.

Paint will be the most durable, in my experience. Guessing you want something transparent like varnish, though.

You are doing pretty much the best already.
Unfortunately nothing lasts forever, just plan on redoing periodically.

I use General Finishes products for a lot of interior stuff but they make a topcoat for Exterior. YMMV

https://generalfinishes.com/wo...-water-based-topcoat

Add a fresh coat of varnish every year and you should be good to go.

be sure to seal the top and bottom of the doors as well. exposed grain will absorb moisture and cause the painted wood to release sooner.

YMMV
John

quote:

Originally posted by arfmel:
Paint will be the most durable, in my experience. Guessing you want something transparent like varnish, though.

I would not rule out paint.
I have considered black paint, but thought that color would attract the Suns wrath.

quote:

Originally posted by armored:
I have considered black paint, but thought that color would attract the Suns wrath.

Yes, it does. When I worked in a milwork shop, one of the items we made custom for people were raised panel shutters and slat blinds. There were primarily 3 colors in the samples they brought in, white, dark green, and black. The black samples were always practically sawdust.
 

Sashco Transformation Log and Timber stain. I put it on my entire house four years ago and it's still good to go. The south and west sides get a ton of hot sun in the summers too and it's going strong.

General Finishes is a good choice, you might also look at Epifanes. I make some exterior products also, but they are mostly for production and not especially DIY focused. Keep in mind that any clear finish you use will allow the wood beneath to darken (if its cherry) or gray. UV radiation, while marginally affecting the coating itself (they are considered "sacrificial") will pass through the coating and degrade the wood fibers.

I also agree with sealing the top and bottom of the door, this will mitigate moisture intrusion and help the finish last longer. If you'd like to talk more in depth, my personal e-mail is in my Member Profile.

I think Marvin makes storm doors that are almost full view. I also think you could get a UV resistant glass (or coating) that would mitigate the deterioration.

quote:

Originally posted by JimTheo:
I think Marvin makes storm doors that are almost full view. I also think you could get a UV resistant glass (or coating) that would mitigate the deterioration.

I removed a storm door because I didn't like the look of it (Half arched)I would prefer a full glass storm door but estimates were in the thousand + price range.
The other problem I encountered with the storm door was the amount of heat created between the storm and house door, I think this contributed to the failure of the door finish.
I may try to build a storm door using the old door as a template.I would want the storm to be full glass with a minimal wood border.

Oil/alkyd based marine varnish is a clear sealer even though it has the motor oil look. Due to the fact it is clear the UV rays of the sun penetrate it and age it fairly quickly. It should be sanded annually and a fresh coat applied. If you do not sand in between coats it will not adhere well and eventually separate between the coats that were applied. If you sand to the point of really fine sandpaper like 320 or finer thinking it will help you are making a mistake. Varnish needs a rougher surface to adhere to. I never sand varnish with paper finer than 180 grit.

In the past I was the lead varnish man in one of the largest yacht yards on the east coast. I have also refinished many old Chris Craft lake boats some of which there are only a handful of models still in existence. Varnish applied professionally is a beautiful finish but needs upkeep, that is where the problems begin. Inexperienced folks think it will last for years with no maintenance. Yacht owners know otherwise!

I take all my quidance from my work on wooden boats. In your case sand to bare wood. Finish with several coats of west system epoxy (the clear version if needed). Topcoat with a quality coating. If you actually only care about survival and it not being visible wood two part poly would be my first choice. Of course if you want the look of varnish you are going to have to deal with varnish. But on top of the epoxy maintenance is way easier.