Deck coating alternative to spar urethane

[Alex_c]

I completed my tinboat project just about a year ago, and I have had some issues with the products I used. I stained my decks (exterior grade ply) with some oil based stain and then coated with 4+ coats of spar urethane. The last coat I applied with a non slip additive mixed in. It worked great but unfortunately the UV resistance has been poor. Everywhere that is exposed to the sun, the finish is starting to crack. At first I thought it was the non-slip additive or the stain that made the urethane crack, but if I lift up a seat and expose an area of the deck that is covered from the sun, the finish is in perfect shape. The undersides of the deck are in excellent condition where I can inspect them, as they are not in direct contact with the sun's UV rays.

So this leaves me with a few questions:

- What is a good cost effective alternative to spar urethane? I have looked at Durabak and Kiwigrip, but both are about $150/Gal and I won't need that much for my boat. Will an exterior deck sealer/stain provide the UV protection I need? I don't mind spending a bit of money, as I am already a bit annoyed with having to re-finish the deck after only a year of hard use, but $150 plus painting supplies is going to be a bit much, considering the wood I'll be coating isn't even worth $100. I would like something that goes on thick and that I can build up. Also something that is relatively easy to re-apply down the road when needed.

- I am guessing I will have to extensively sand down the old finish to get rid of all the high spots where the top layer of ply has started to crack. It's not de-laminating, but when it gets wet, the wood will swell under the cracks in the varnish. Should I completely sand all the old finish off, or am I ok to scuff it up enough for the new coat?

- How long will my deck last if I just leave it as is? Might be more cost effective to re-do the deck in a couple years with a more UV resistant finish, as opposed to spending $200+ on refinishing that may or may not extend the life of the wood by that much.

 

[surfman]

Maybe get a cover so that it is not exposed to the sun all the time, otherwise you will need to redo the wood by sanding it all the way down, Try using a non-urethane varnish, I am not that familiar with varnish but I know that some are made using urethane and some are not.

 

[Frank R]

Exterior grades of plywood are prone to checking due to the wood species used. The general rule of thumb is to use marine grades of wood or to cover the plywood with fiberglass cloth and epoxy resin.

Epoxy makes an excellent primer but it degrades with UV light. So it has to be covered with a UV resistant spar varnish.

Note that what is called "spar varnish" can be very different products. Do not use spar urethanes, the ones that are commonly available at the big box stores. You want a marine spar varnish, the old fashioned kind that uses tung oil. Man O War Marine Spar Varnish is an inexpensive one sold by the quart for around $33.

 

[Alex_c]

Fiberglass and epoxy seems like it would be just as costly as using a UV resistant coating like kiwigrip or durabak, and probably more work since I would have to remove the decks to properly apply the glass.

I keep it covered as much as I can, but UV exposure is ultimately inevitable in the summer.

 

[surfman]

Can you post pictures of what you are talking about, not sure if it is the wood that is causing the problem or the actual paint.

 

[lckstckn2smknbrls]

Do you want to see the wood grain? If not use an oil based enamel paint like Rustoluem.

 

[Alex_c]

I think it's the wood that's causing the problem now that I think about it. However, the coating is starting to flake off. I'm just going to re-sand it and put some oil based exterior deck paint I think.

 

[Ringo Steele]

Hi Alex,
I am having the same issue with the spar urethane I used on my flooring I installed last year. I am planning to strip it down and use the "Deck Restore" type product on mine, as is is non-slip as well as durable under foot. I sure will miss that woodgrain, though.

 

[Alex_c]

Wow, great job on the floor using lumber instead of plywood. I have looked at a few options - I'll post up on here once I re-coat it.

 

[zrxfishing]

Love that floor Ringo!!

 

[Frank R]

Ringo Steele » 02 Jul 2014, 10:37[/url]"]Hi Alex,
I am having the same issue with the spar urethane I used on my flooring I installed last year. I am planning to strip it down and use the "Deck Restore" type product on mine, as is is non-slip as well as durable under foot. I sure will miss that woodgrain, though.

That is too nice to cover up! Strip it and re-varnish with a good quality tung-oil based spar urethane.

 

[Ringo Steele]

Thanks Alex and Frank, Any product suggestions appreciated... I used Minwax Spar Urethane, which is supposed to be UV resistant, but they must have left it out of the batch I got! :roll:

 

[Frank R]

Man O War Marine Spar Varnish is an inexpensive one sold by the quart for around $33

And you have to re-varnish every other year at least.

 

[RustyGoat]

I used porch and floor paint on the floor and deck panels on my build. It's only been on a couple months on a garaged boat but seems to be really durable and holding up well.

 

[Alex_c]

The checking took about 3 months of sun exposure to show up. Still haven't re-coated. Fishing is in full swing and I have a few other things I need to do to the boat.