Fir Exterior Door Finishing Advice Please

[Gabe Caraway]

Here's what I've got so far -

I jambed the rough opening with select pine from a big box store. The door is heavier than a bag of bricks so I glued up 2 - 1*6s and ripped them down to a 4.5" jamb. I sanded 3/4 sides to 320 grit so they would take a good stain. Wood conditioner first, of course.

My question concerns the door. I assume everyone would go ahead and sand the door to 320 as well. It doesn't feel even 150 straight out of the packaging. It will also be stained and there was good advice on the packaging about alkyed based this and that before oil-based those and these.

Questions:
1. Would you sand the fir door to at least 320 or more?
2. What sort of clear-coat would you use for a door underneath approximately 4' of soffet - poly, epoxy?

I suppose I could treat it like outdoor furniture and just coat both sides with Mixwax Spar Urethane with UV treatment. Do doors deserve better?

Thanks,
Dude with rookie questions.

[Peter Quinn]

I would stop at 180-220 on the sanding. IMO a door is not a piece of fine furniture, more "tooth" is better for finish adhesion, no need to polish the surface, and frankly fir won't benefit much from it IME. Fir has those hard and soft layers that cause it to sand a little irregular, the soft layers wear more quickly under the sand paper and form little valleys, the hard layers appear as ridges, its never really smooth like a hard wood. For finish I'm no expert, but my current thinking, having probably though and read a bit to much about it, is white paint. Yes, the best finish for the front of the front door is probably the the best finish for a life guard's nose, a thick coat of zinc oxide in a binder.

Assuming that won't fly, I like a clear penetrating epoxy sealer. Smiths is one manufacturer, available at Jamestown hardware among others. Not sure where you are located but not every state will allow that much VOC. But you can make your own sealer by combining epoxy with solvents that are readily available. Lots of good info at epoxy products.com (no affiliation ) too. Hard site to navigate, so look around, good info and testing hidden in there. Look at their low V epoxy. Mix it with xylene, you have your own penetrating epoxy sealer, much cheaper than some other options. Pretty sure you can thin west systems with acetone or xylene too for the same effect. Point is the epoxy keeps out the water, or mitigates its effects, and thats good. The second enemy of exterior wood is UV radiation. So the top coat needs to have a heavy UV blocker, and be flexible enough to stand the seasonal movement of wood. Epifanes is a name that comes up often as the best, there are also water based now coatings now that do well. General and target are two companies that make exterior WB clears. UV exposure will break the bond between finish and wood and eventually break down the top coat. A clear with good UV blockers, much like sun block at the beach, will delay that inevitability to the extent it is able. Thats where the white paint come in. Much more effective at blocking UV than any clear available. And a good umbrella is still effective at blocking direct uv exposure. A wide soffit is good for rain, and it cuts some of the worst direct UV rays, but a portico or some type of roof directly over the door is better. Not always possible I know, just good to keep in mind.

The other end of the spectrum is an oil finish. Lasts between 6 months to 3 years depending on exposure. If the door is going to see regular exposure to water I don't recommend an oil finish at all, not enough protection IMO. So you have to reapply this type of thing annually, or biennially, but its a simple sanding sponge and wipe or brush on coating. Looks very natural. On the plus side most offer moderate UV protection if the finish is maintained and they are way easier to reapply than a film finish. Have you ever sanded all the varnish off a peeling door? Not most peoples idea of fun. Of course if you catch the varnish earlier, you can scuff sand that and recoat, not as easy as an oil, not as hard as a complete stripping. The best oil I've seen is Messmers UV plus. Its very stinky, makes my head hurt and my eyes water, do wear a respirator with that one. Cabbot and a few others make similar products, messmers seems more more durable IME than most.

If your plan is to stain, then epoxy, then clear, I'm not sure what the schedule should be. Most epoxy sealers have a lot of solvent, the kind that reactivates an oil based stain. So I'm not sure how you apply that schedule. I'm working on a door presently, or will be shortly, QSWO, going to seal with epoxy then clear coat with General exterior WB. My plan is to fume it, but that wont work with fir.

[Mark Wooden]

Yeah, what Peter said. You won't go wrong.

[Gabe Caraway]

That is an amazing response. I'll need to re-read that a couple times; thanks, Peter.

[rogers kevin]

I would definitely coat it and I just found a great outdoor transparent stain for my wood from Storm System (http://www.stormsystem.com). This exterior stain is not only moisture protectant, but also prevents UV damage. It comes in three different options depending on the exact specifications you are looking for!

[Kent A Bathurst]

"Epifanes is a name that comes up often as the best..............."

Agreed. I used it on a commissioned WRC arbor/gate/garden entrance. 4 years in the Georgia summer sun, still looks like it did when it left the shop.

No experience with WB, so not commenting on that - just on what i have experience with.