LumberJocks

Pressure Treated vs. Poly Coated for Outdoor Use

  • Advertise with us

« back to Wood & Lumber forum

Forum topic by wilschroter posted 06-22-2020 02:22 PM 423 views 0 times favorited 16 replies Add to Favorites Watch
View wilschroter's profile

wilschroter

144 posts in 1328 days


06-22-2020 02:22 PM

I’m going to be creating a top “cap” to the railing of my new deck, and I’d love to use a poplar or similar wood that’s fully coated in polyurethane to get me a clean, modern finish. Has anyone here had any luck treating outdoor wood with poly and have it hold up to the elements? My alternative is to paint/seal a pressure-treated board, but they just don’t have a very clean finish.


16 replies so far

View OnhillWW's profile

OnhillWW

247 posts in 2035 days


#1 posted 06-22-2020 04:00 PM

I’d rethink this. Poplar is a poor choice, not rot resistant, low strength and soft when compared to better options. Also Poly is not a good choice, low UV protection and not well suited for the expansion / contraction of wood in an outdoor setting. Spar varnish is made for such situations , think wood boats but be sure you purchase a quality version and not the big box run of the mill versions as they are nowhere as good as something like Epifanes and others.
Good luck.

-- Cheap is expensive! - my Dad

View ibewjon's profile

ibewjon

1754 posts in 3596 days


#2 posted 06-22-2020 04:24 PM

Agreed. Use a high quality spar varnish, not water based. And even that ages and will need to be recoated every couple years. White oak will cost more but be a much better choice.

View wilschroter's profile

wilschroter

144 posts in 1328 days


#3 posted 06-22-2020 04:35 PM

This is exactly the feedback I’m looking for so thank you.

So if I were to use a pressure-treated 2×10 (that’s my cap width) that I sanded down, painted black (the color I’m shooting for) and then did a spar-varnish over that, it would probably be my best bet?

View Fred Hargis's profile

Fred Hargis

6310 posts in 3296 days


#4 posted 06-22-2020 04:43 PM

If you’re going to paint it, why add anything else…the paint should do just fine (assuming proper application). Back to the spar varnish…what they refer to is not “Helmsman”. Look for a true marine spar varnish; but like I said I don’t think it does anything for you.

-- Our village hasn't lost it's idiot, he was elected to congress.

View wilschroter's profile

wilschroter

144 posts in 1328 days


#5 posted 06-22-2020 04:48 PM

Oh that’s interesting. You’re saying that the paint itself negates the need for a varnish to keep it clean/crisp/protected?

View Fred Hargis's profile

Fred Hargis

6310 posts in 3296 days


#6 posted 06-22-2020 05:23 PM

Yep, if it’s a good exterior paint over an oil based primer (at least that’s how I would do it). Make the exterior paint an oil based as well and it will really last a good long time….but an acrylic top coat would work quite well. If it’s pressure treated be sure to give it time to dry out before painting.

-- Our village hasn't lost it's idiot, he was elected to congress.

View wilschroter's profile

wilschroter

144 posts in 1328 days


#7 posted 06-22-2020 05:34 PM

If I sanded it down and used a good primer, could I get pressure-treated 2×10s to have an almost furniture-grade smooth finish? I know I’m asking a lot out of PT timber, just curious if any of you guys have seen PT-stuff brought to a high level finish.

View Fred Hargis's profile

Fred Hargis

6310 posts in 3296 days


#8 posted 06-22-2020 05:52 PM

That could be tough to do, but I’ve not tried it myself.

-- Our village hasn't lost it's idiot, he was elected to congress.

View Axis39's profile

Axis39

261 posts in 400 days


#9 posted 06-22-2020 06:57 PM

Aren’t you supposed to let PT lumber dry a while before finishing it? (I’m not sure with the new coatings and haven’t done a lot of stuff like that in the last few years).

My first thought was ipe, but is a pricey endeavor (both the wood and the blades you’ll need to replace!). Maybe a different tropical wood, or a wood that grows near water?

No coating is going to be maintenance free for long. You might get a year or two out of some, maybe longer out of others. Especially if they are seeing direct sun. I like the idea of exterior paint. But, definitely go with something designed for it, like a deck stain/coating, or as mentioned spar varnish.

-- John F. SoCal transplant, chewer uppper of good wood

View LittleShaver's profile

LittleShaver

681 posts in 1422 days


#10 posted 06-22-2020 07:49 PM

I would recommend a good trim paint over a suitable primer. House paints hold up pretty well over time even with constant exposure to the elements. Since this is a top cap and shouldn’t see direct ground contact, you can use just about anything sold for exterior trim. Granted, white oak, ipe, and mahogany are great for exterior work, but just look around the neighborhood, no one has exterior trim made out of these. Save the money you would have spent on great wood and spend it on great paint.

-- Sawdust Maker

View Redoak49's profile

Redoak49

4798 posts in 2791 days


#11 posted 06-22-2020 08:22 PM

My deck is #1 pressure treated 2×6. I looked at alternatives for the railing and ended up with Trex and been very happy. I just do not have good luck with painted pressure treated wood in my climate. With the change in temperature and humidity, the wood is constantly moving.

View wilschroter's profile

wilschroter

144 posts in 1328 days


#12 posted 06-23-2020 12:28 PM

Yesterday we had some hard rains followed up by humidity and I’m watching my PT boards warp before my eyes (no huge surprise). So yeah, trying to create a perfect frame out of these boards is going to be difficult.

Tons of decks get built with wood railings though. What are you guys doing to keep these things from twisting over time? This is my first deck, so go easy on me ;)

View Axis39's profile

Axis39

261 posts in 400 days


#13 posted 06-23-2020 01:22 PM

I’ve never seen new growth pine stay straight! If you look at the ring count, you’ll see how wide the growth rings are. Lotta soft wood there. I have some southern yellow pine that was cut down in 1855… It’s got hundreds of rings per inch. It’s really, really stable.

One thing about buying framing/PT lumber, get it installed quick… If you can., there is a chance it’ll be a while before it goes completely wacky. We used to leave hacks of 2×4’s banded as long as possible for this reason. Screwing pieces together slows down the warping and twisting… Hence, my suggestion to get it installed as quickly as possible.

But, water and pine usually just aren’t very compatible… But. it’s what we have and can usually afford.

-- John F. SoCal transplant, chewer uppper of good wood

View bmerrill's profile

bmerrill

106 posts in 876 days


#14 posted 06-23-2020 01:31 PM

Use a composite or PVC deck board. Azek/TimberTech have wide 7” boards.

-- You are not told the truth, you have to learn the truth.

View tbone's profile

tbone

312 posts in 4487 days


#15 posted 06-23-2020 03:14 PM

Another consideration might be the black paint on the hand rails. Down here in Texas it might burn your hands on some days. Just a thought.

-- Kinky Friedman: "The first thing I'll do if I'm elected is demand a recount."

showing 1 through 15 of 16 replies

Have your say...

You must be signed in to reply.

DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

Latest Projects | Latest Blog Entries | Latest Forum Topics

HomeRefurbers.com