I've been commissioned to carve some cedar posts for an outdoor porch. I need a durable finish to keep the carvings intact. I've heard about marine varnish or clear penetrating epoxy. I'm very experienced with indoor finishes, but outdoors is another thing. I would appreciate suggestions and brand recommendations. Thanks

Epoxy is not an outdoor finish. It gets hammered by the uv.

Marine varnish is high maintenance. Somebody needs to coat it once a year.

There are penetrating/thin build products made by Sikkens. Do not listen to negative people who used it 20 years ago. They have 6 different products all excellent. When it was first introduced to the US back in the 90’s it was marketed to the boating industry as a teak finish. It didn’t look good back then on teak. Products are different and cedar is a perfect wood.

Understand what you're going to be dealing with on exterior grade finishes. You have two basic options, NEITHER of which will ever stand up to the brutality of UV exposure, extreme temp fluctuations, and rain/humidity/freezing. All of in time will need TLC.

1) Thick film finishes. They all vary in their durability, and you can spend as much money as you want here. If you require high gloss, this is your only option. Expect the sheen to last maybe a year, regardless of the initial sheen. Old school SPAR varnish is reasonably decent and also not too difficult for the customer to rescuff and brush on a maintenance coat. There are post-cat products available but I honestly doubt their value in most case.

2) Thin film and oil finishes. Sikkens, mentioned by Adam, is a reasonable option. I've used a little of it here and there and always liked it. It looks like an oil finish.

Thin films and oils don't ever really have that "deep" look that thick varnishes have. But thick varnishes flake, peel, and look wretched after a few years if they don't get maintenance coats.

Personally in your shoes I'd punt this to the customer and see what they expect. Either way, I would not warranty the finish the way I would an interior product. Put everything in writing and make sure all options spell out specifically that exterior finishes WILL take a beating.

Actually epoxy (West systems) is used as a stabilizer in the marine/boat finishing. They use it to build film thickness and keep the wood from moving as little as possible and then a couple of topcoats with a good marine varnish (Petit marine) . It's called bright work and has to be maintained on a minimum 2yr schedule.
I've done live edge wood tables this way and it's time consuming but it looks great.

The problem I see with the soak in types such as Sikkens or TWP is if you let it past its recoat window you're in a world of hurt having to strip/sand it off.

If it were on my porch I'd just throw an exterior grade oil like Watco on it. If it's in the shade you could maybe get 2 years. Just clean it or pressure wash with a small home unit, let it dry and reapply. Much more user friendly.

my2cts
cheers

Bart,

I’m a brightwork/ boat guy. You are technically correct in the way epoxy is used outside. However, no one with any experience does it. We do use the epoxy, varnish on things inside the boats like the sole(floor) to build quickly.

The problem outside is epoxy gets trashed by the uv big time(west system makes an additive that temporarily helps). On the boats the wood gets damaged frequently. Now you have bare wood, some epoxy , and some varnish at the ding site. How do you fix it? It looks terrible after recoating. Whereas with just varnish, you simply sand it and coat it.

This TotalBoat varnish is hands down the easiest varnish I have ever used. I used to use Petit Flagship on my brightwork, and it took forever to get any kind of buildup. With Lust, you really can get 4 coats in on the same day. The shine is excellent and the only advice I would give you is to thin it a bit to get it to flow out better.

By following the manufacturer’s instructions, I’m able to get the desired finish. Thanks to its classic spar formula with a modern twist. It’s ideal for exterior and interior wooden parts and brightwork on boats. It is the best marine varnish for me as it keeps my boats looking good.