Using Rustoleum Enamel

[catleppert]

Hi there -

This is probably a stupid question, but I am going to ask anyway... Planning on using Rustoleum oil-based enamel paint for my outside sidewalls. My question is - do I need to spar urethane the wood first? For extra waterproofing? Or is the enamel enough if applied correctly? Our plan is to use a HF sprayer. If that plan doesn't pan out, will just roll on.

Any insights would be appreciated....

Theresa

[les45]

I used Rustoleum for my topcoat. I primed it with two coats of Zinsser oil based primer over the bare plywood (the primer pointed out some of the small blemishes that still needed filled and sanded). Check my build journal for some helpful hints on how to apply the Rustoleum. I applied three coats and I found that cutting the topcoat of Rustoleum with 25% mineral spirits made it flow on with a 4" foam roller with a final finish that looked sprayed on (no roller marks).

[48Rob]

Theresa,

No, the varnish is not needed, oil based paint will seal the wood the same way the varnish will.

That said, it is important to understand the the wood must be well sealed by whatever coating you apply.
"Just" spraying/rolling/brushing a coat or two may not be enough.
The wood needs to be well sealed, not just pretty much sealed.
To that end many, including myself, thin the first coat of paint or varnish a bit with mineral spirits (25% MS. to 75% paint or varnish) to be sure the paint soaks in a bit, and really adheres well.
You may well need 5-6 coats, with sanding between, to make the wood waterproof.
Don't forget edges, cuts, screwholes, and hidden areas, you may not be able to see them well, but water will find them.

Rob

[les45]

Rob makes a good point about sealing the wood. I forgot to mention that I sealed mine, including all edges, with four coats of CPES before starting the paint system. Some people say you only need one coat of CPES but it goes a long way so I just kept putting it on until I ran out. I figured it couldn't hurt anything to have too much. I also used 4" fiberglass tape and epoxy on all joints. One thing to think about as you do your prep work is to make sure all the materials are compatible, including your fillers. Some fillers, like Bondo, are not compatible with epoxy systems. I used the Zinsser primer because it is compatible with just about everything.

[catleppert]

Thanks, Len and Rob, for taking the time to respond! Mineral spirits 25/75 and paint it is, at least for a couple coats and then multiple coats full strength - and of course sanding in between. Lots of work, but necessary!

[les45]

Thanks, Len and Rob, for taking the time to respond! Mineral spirits 25/75 and paint it is, at least for a couple coats and then multiple coats full strength - and of course sanding in between. Lots of work, but necessary!

Don't forget to do your top coat thinned to 25/75 also. That will make the paint flow evenly without any roller marks. Looks like a sprayed on finish when it dries.

[catleppert]

Les, also sent you a PM. Did you sand between your last coat of full strength enamel and the final coat of thinned? Or just do the thinned coat right on top of the full enamel?

[les45]

Les, also sent you a PM. Did you sand between your last coat of full strength enamel and the final coat of thinned? Or just do the thinned coat right on top of the full enamel?

Answered in PM response.
Larry S.

[catleppert]

Thank you Larry!