Garage doors: Must I paint, or can I varnish/polyurethane/???

I'm building garage doors for my new shop; The skins are okoume marine plywood, edges banded with Sapele (much like mahogany). They look quite nice, and I'd love to leave them looking like, well, wood. But it seems clear that paint is always way more durable, and the span between needs to touch up or refinish are going to be stupid for an area totally about 26'x9'.

The doors face north, and 2/3 of them will be under an awning.

What sayeth the hive? Should I give up on this appearance item for all the recurring need to stop working on cars and work on the doors, or is a carefully chosen finish going to be durable enough to get withing ballpark of paintlike durability? Any product recommendations?

I'm going to be doing some short handrails on the house that will have more exposure and plan to do a marine style finish of epoxy coating followed by varnish to protect the epoxy from UV, but that's too involved for 234 square feet of door, I think...

A good quality exterior clear finish with UV protection should be fine, and should last as long as paint.  I'd look at marine products; I forget the brand but I used a marine varnish on my front door and it's held up really well.  Find a marine/boat shop in your area and see what they have in stock.

In reply to stuart in mn :

Awesome, thanks for the info! How long has your door lasted so far, and what sort of conditions does it see? I'm guessing from the "in mn" part that it sees harsher winters than I'm going to get here in Oregon...

I fully support no painting that perty wood.  Just know that any varnish or poly you put on it won't last as long.  I remember at my house growing up it was always my job to re-do the entry doors every 5 years.  They never saw water (behind storm doors and under a dormer) but the UV would kill them.  That was the 80s, so I'm sure they're much better on the UV protection.  Maybe every 10 years?

I would look to a Marine Spar Varnish with the highest rated UV resistance.  Keep in mind that "spar varnish" is a very vague description.  It can be a polyurethane, a urethane, or an oil finish.  The term Spar comes from nautical terms, a spar being a generic term for the masts that hold the sails.  Spar varnish has now come to mean anything for outdoor wood and its main property is that it is flexible and elastic.  Since masts are constantly flexing and since outdoor woods expand and contract with weather, the term spar varnish basically means any coating that doesn't dry hard and brittle.  That quality is very important, otherwise the first swing in temperatures could put fractures and cracks in a different, harder finish and allow water in.

I might suggest you call Zar Finishes at 1−800−272−3235.  Bonus is they are an American company.  You might not know the name, but they're the folks behind names like RustOleum, UGL, Drylock, and Zinnser.  They have a wide variety of canoes... I mean products for exactly what you're doing.  Honestly not a canoe, I'm just so happy with how all of my Zar projects turned out that I like to shout it from the rooftops.

My guess is they will point you toward this:

Also... Pro tip.  (from an amateur)

Regardless of your desired finish (matte, satin, gloss), Do your first few coats with gloss.  All of these finishes are the same gloss urethane to start with, then they add flattening agent to get the desired finish.  So a Matte or Satin urethane has more stuff that isn't urethane mixed in.  If you do the first few coats with gloss, your urethane resin solids concentration is of notably higher density and therefore stronger.  After your first couple base coats in gloss, step back and see how you like it.  If you like it, finish it off with gloss.  If you don't, do your last coat in Satin or Matte.  The last coat you put on determines the sheen, so might as well use the strongest sheen (gloss) until your last coat.

Back when I did floor refinishing classes for a big box store, I told people to do 4 thin coats in total.  I would sell them enough poly to do all four coats in gloss, then also sell them enough to do one coat in the sheen they think they want.  I told them to do three coats in gloss and see what they think.  Do the last coat in whatever sheen they like and return the unused quantity.  It was usually 50/50.  Sometimes people stuck with the sheen they pictured, and sometimes they liked the gloss and returned the satin.

This process is A) a way you get to look at one finish before your final decision, and B) a way to make the finished coating stronger.

Is there a reason why an automotive clearcoat would be a bad choice here? They seem to tolerate UV and the elements better than most regular clear finishes.

If I knew anything about automotive finishes, I could answer that intelligently.

Thank you! I'll check out Zar.

I don't know how to even approach the question of automotive paint and whether it makes sense to look into.

I want to just say "if it were better for this, why would there be exterior home treatments or the marine finish industry?" but ruling something out because someone else is selling stuff doesn't seem like a pure application of logic...

I imagine there are significant differences between porous and (relatively) non-porous surfaces, and a difference between the flexing auto parts do that those flex agents have to deal with vs less bending but more expansion/contraction that wood does... But I don't know who to ask to get a real answer.

Curtis73 (Forum Supporter) said:

If I knew anything about automotive finishes, I could answer that intelligently.

This is the internet, don't let that stop you 

Jesse Ransom said:

Thank you! I'll check out Zar.

I don't know how to even approach the question of automotive paint and whether it makes sense to look into.

I want to just say "if it were better for this, why would there be exterior home treatments or the marine finish industry?" but ruling something out because someone else is selling stuff doesn't seem like a pure application of logic...

I imagine there are significant differences between porous and (relatively) non-porous surfaces, and a difference between the flexing auto parts do that those flex agents have to deal with vs less bending but more expansion/contraction that wood does... But I don't know who to ask to get a real answer.

I did paint an old aluminum boat with DuPont Imron once.  My nephew bought it from me and still uses it all the time.  If it stays in the water for more than about 2-3 months (which frequently happens in the summer) it get's bubbly like the skin of a toad.  Once you take it out of the water, two months later it's like nothing ever happened.  Ran onto a guy at a gas station who had the exact same experience.  He called it "slow paint."

In reply to Curtis73 (Forum Supporter) :

I'm a little weirded out that when I called Zar they did indeed point me to the above, but also to the water-based version, and asserted that the only difference would be soap & water vs mineral spirits cleanup. I even clarified that they were asserting no difference in durability, which they confirmed.

That kinda flies in the face of everything I've read, which indicates that oil-based will absolutely be more durable/weather-resistant than water based poly.

I'm stoked to have a recommendation, but Zar's claims give me pause. Anyhow, the oil is okay to apply quite a bit cooler, which is a big deal for me, so as long as their products are good I guess it doesn't matter if the water based isn't as good since I probaby can't use it anyhow... I just always hate it when companies say stuff that makes me question their forthrightitude...

STM317 said:

Is there a reason why an automotive clearcoat would be a bad choice here? They seem to tolerate UV and the elements better than most regular clear finishes.

This is okume with automotive clear shot over it. It also had a coat of west systems epoxy though to help protect the wood from moisture.

In reply to Jesse Ransom :

You might be surprised.  Water-based polys ain't what they used  to be.  They successfully steered me to an oil-modified for my hardwood floors.  Oil modified is kinda half-way between.  It uses oil-based esters emulsified in water.  I wanted the depth and dimension that oil gives to woodgrain without the darkening of an oil poly.  I got exactly what I wanted.  I'm about 1.5 years in to my flooring and I'm pleased as punch.  I got the grain-highlighting effects of oil-based without any of the darkening.  I don't worry about water (and for that matter, I don't worry about scratches or anything else either)  I wouldn't be afraid of the water-based, but based on my experience with other brands you can expect 3/4 the life or better from water-based finishes.  The only real difference between the two is what the esters are suspended in.  An oil based poly uses volatile oils  and a water based poly uses water and an emulsifier.  In each case, the carrier evaporates leaving just the poly behind, so in theory the end product is the same.  In reality there are differences... I'm guessing in how the poly "knits" together.   The water is way easier to clean-up but I wouldn't let that be your guide.  If you want the rich depth of oil based, go for it.  Just put your brush in a plastic bag between coats and throw it away when you're done.

I think there will be a time some day when the choice between oil and water will be aesthetics alone.  Water based finishes are coming along very quickly.  If Zar says either one, I would take them at their word.  Suffice it to say that my floors were my first dive into anything but oil-based and I'm VERY happy I listened.  The fact that I could do 3 coats per day and it was ready for walking the next morning was a bonus.  The lack of odor was a bonus.  The non-darkening was a bonus.  Edit:  That is to say, I don't think Zar is pushing whatever they can sell, I get the impression that they are earnestly trying to find a product that will make you happy, not make you angry and lose a customer.

Oil based will darken a bunch on the first coat and a little more with each additional coat.  Water based will stay really close to what it is right now with an almost imperceptable darkening, but it won't gve you the contrast in the grain like oil.

1SlowVW said:

STM317 said:

Is there a reason why an automotive clearcoat would be a bad choice here? They seem to tolerate UV and the elements better than most regular clear finishes.

This is okume with automotive clear shot over it. It also had a coat of west systems epoxy though to help protect the wood from moisture.

Sexy hydro.

I think the big concern I would have with automotive finishes is the porous substrate... which you solved by epoxying first.  I'm no expert, but I would think that a coating designed for a non-porous substrate wouldn't perform as well on something like wood.  Kinda like using wood glue on glass.  It's not going to stick.

In reply to Jesse Ransom :

Also to follow up without another edit.... find a local Zar dealer, and by that I mean find a Jimbo's Paints, not an Ace Hardware or Home Depot.  You want a Jimbo who opened a paint store because Jimbo knows paints, not a national chain that happens to sell paint and hires minimum wage folks who only know the difference between a tractor and a bird feeder.  My local dealer (about 30 miles away) was stoopid helpful.  I took a sample of my maple flooring and a guy walked me through all of it including putting sample finishes on the piece I brought.

I would also find your closest Woodcraft or other woodworking store.  Those tend to be staffed with lifers who know their wood (snicker).  My local Woodcraft store is full of highly skilled craftsman whose passion is wood.  They are the GRMers of woodworking.  This is their hobby and their life.  Ask them about oil vs water.  One of them will likely be that guy who knows it all, just like one of us here knows every difference between an NA and an NB and can tell you which Miata is right for you.

The water based poly's that I've seen applied and read about have a risk of appearing cloudy.  If this was me and mine I'd be doing oil based every time when it comes to top coat.  

Cool, this is shaping up nicely!

The oil is good for application ten degrees cooler than the water, which pretty much makes my decision. It's not going to be awesome moving the doors into the attached garage to keep them warm enough, but it's doable. It sounds like aesthetically I'd rather do the oil anyhow. I'm actually really stoked that the recoat time should facilitate doing a door a day. I think once I rip enough sapele for the rest of the doors' edges (and stop filling the air with sawdust), I should be able to finish a door, build a door, and rotate each day and have a full set next week...

As a bonus, the two local dealers are the local paint shop I've dealt with the most for other house painting, and my favorite local woodworking shop. That seems like a good sign.

Fast I'm not, but getting to a milestone I'm going to wring every bit of victory lap out of it... Thanks for the recommendation, Curtis!

That's pretty!

In reply to dculberson :

Thank you! I'm pretty well pleased. I'm a little concerned as they're  tight fit and sort of "cam over" as they close. I might need to figure out how to shave a little off the edge of the last door. And they definitely need a strip over the center joint and a couple of other weatherstripping details. And then there are the next four panels to build for the larger opening... But it's still a milestone!

I was really worried that my whole plan for door construction and hanging was cockamamie, so it's a big relief that they feel solid, open and close smoothly, and the tracks don't feel like they disagree with the hinges or vice versa. You know how that is with any big project from scratch and outside your area of expertise... "Is this going to look like someone turned sixth grader loose with power tools?"

Those do look great!  I think you'll be really happy, and I hope the exterior stuff lasts as well as their interior stuff.

In reply to Curtis73 (Forum Supporter) :

Thanks! After seeing the first doors in place, I'm feeling better about the decision to chance it a bit even if it does need more maintenance than paint.

Thanks again!