The Rot Doctor


Subject: CPES, etc
Date: Tue, 07 Sep 1999

Hello Dr Rot:

I have a Victorian (1885) that I'm slowly restoring and one of my projects involves stripping the paint off redwood T&G (with beading) in one of the bathrooms. I'd like to leave the wood natural because of it's beautiful appearance and thought it might be a good place to use some of your CPES.

1. Will the CPES discolor or darken the redwood any more than any other sealer, finish?

No, CPES has the same color effect on wood as a thin coat of clear varnish.

2. Is another coating over it necessary to protect the wood from the steam, moisture of the bathroom environment?

In your particular case, I'd say yes, it would be a good idea.

3. If so, will it accept any coating I want to put over it?

Yes, any coating, with polyurethane clear coatings having -- we believe -- the best adhesion. Our experience has been that ANY coating over CPES treated wood last a significantly longer time than coatings without the CPES wood treatment.

4. What would you recommend as a finish coat for that environment--spar varnish, varathane, ... or anything you have available?

A polyurethane marine varnish. We don't sell them, but any marine store does. No particular brand preference.

5. One of the people helping me used oxalic acid to bleach some of the wood. Will there be any problem applying CPES over this treated wood?

No problems.

Note: Some wood finishers choose to wipe down the CPES application to smooth it out approximately 5-10 minutes after application. They use a clean, lint-free dry cloth. After it cures (24-48 hours) the surface can be sanded.

When filling cracks (after the application of CPES) in window sills, do you recommend Fill-It Epoxy Filler, Layup and Laminating resin, or something else. I imagine the expansion - contraction, especially between horizontal and vertical elements of the trim present a unique problem.

Either the Epoxy Filler or the L&L Resin will work. The L&L Resin is used if there are relatively inaccessible areas that the Epoxy Filler cannot be easily pushed into.

Wood expansion/contraction does present some problems, but not usually to a premium epoxy. The bond is so strong that there is no separation. Further, our resins retain a slight flexibility that standard epoxy resins do not. This helps.

I've also got a front porch that was improperly installed. They didn't prime or seal the backside of the 3" wide T&G and consequently, the expansion - contraction opens and closes the joints a good 1/8 inch during the changing seasons. Would it be possible to wait until the joints are tight, flood the wood with CPES and have any chance of having it penetrate enough to stop or reduce the expansion and contraction of the wood? As it is, it's impossible to prevent water penetration through these joints during the summer.

No, CPES won't help you here, nor will any rigid or semi-rigid adhesive. If you wish to close them, then the edges should be CPES treated and a premium flexible caulk such as 3-M's 5200 applied. It will stick and has the elasticity to make the 1/8" expansion/contraction. The best time for application would be during the contracted stage when the gap is the widest.

My final question concerns the installation of new front steps to the building. I've already purchased 8 foot long oak stair treads to replace what is already there and I'm wondering if an application of CPES would make them virtually bullet-proof? I plan on painting them as if they were any other wood - due to the necessity of providing some traction (sand, ground walnut shells, ...) in wet weather - any other ideas here?

Absolutely DO apply CPES to the new wood, ESPECIALLY the edges and all end-grain locations. Apply as much to the end-grain as the wood will absorb. I wouldn't want to say that the treads will be forever rot-proof, but very nearly so.

It looks like I'll be obtaining a considerable quantity of material from you in the future as there are wooden rain gutters, vulnerable windows, this two story, 6,000 square foot house. Your products appear to be ideal for much of what I want to do -- protect what's already there.

Right, that's what the CPES is good for -- saving what exists and protecting it from future harm. CPES in non-rotted wood will cover approximately 200-300 sq ft/gal, the variable being the absorption rate of the wood.

Thank You

Greg P.


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