The Rot Doctor


Subject: information please
Date: Fri, 05 Mar 1999

Dear Doc:
My wife and I are still in the "research phase" of building a log home. I am a carpenter by trade, but have no experience with log construction. The preservative & insect prevention aspect of log construction is thoroughly confusing to me. I have read publications that suggest that you mix concoctions in which to soak the logs. At present, the preservative is the only part of construction that has me scared. I read about your product & have a few questions.

* Does CPES have any insect repelling qualities?

Yes, but see discussion below.

* Is CPES all you need to apply to logs for reasonable protection against moisture?

Yes, but see discussion below.

* What is the expected coverage from a gallon of product?

Depending on the absorbency of the wood, between 200-300 sq ft per gallon.

* Should CPES be applied to the entire log before construction or should it be applied after construction is complete?

After construction is complete, unless you see signs of wood deterioration on the raw logs, in which case you would treat that area prior to construction.

* How often should CPES be reapplied?

As a surface treatment for general protection, every couple of years. For treatment of rot or deteriorated wood one proper treatment will be all that is needed.

Any information would be appreciated.

Thank you in advance for your assistance,
Jay & Amy

Jay & Amy:

You ask some good questions and are right to be concerned about wood preservation. This problem gets some log home owners into bigger problems than they had anticipated.

Rule #1 is keep the water off the logs. Try and design the house so this is done as much as possible.

Whether the logs should be treated before construction raises a lot of issues. Much depends on the type and condition of the logs. If they are aged and dry then they will absorb treatments readily, including CPES. If they are still somewhat *green* then they won't, because the sap and moisture won't allow good penetration. This is why we suggest that you wait until the home is constructed before thinking about the raw wood treatment. The only exception I would make to this is that all log juncture points be treated with CPES before assembly. The CPES will soak/coat the wood and give strong resistance against rot in these areas, which are not so easily accessed after construction. Nothing will protect wood better than a top-grade penetrating epoxy. But epoxies -- all epoxies -- are expensive, and to treat every bit of every log would cost thousands of dollars. This is why we suggest treating just the vulnerable areas first and then keeping good vigilance on the structure as it settles and ages. Another vulnerable area that can be usefully CPES-treated is the log juncture lines before the application of chinking. You just brush on the CPES, give it a few days or so to cure, and then apply chinking. Chinking will stick just fine to CPES-treated wood.

Soaking raw, dry logs in immersion baths of petroleum preservatives (like kerosene/wood tar/japan drier) will go a long way toward preserving the wood, but you'll end up with dark logs and a strong odor. It was done in the old days when nobody cared. There are modern versions of this kind of formula sold by log home builders and log home suppliers, and for all I know they are just fine. The good ones have UV protectants (which are expensive and there must be enough in the mixture to do some good) and should be used.

But no matter what you do, wood rot will eventually appear sometime, somewhere. And this is what you attack with the CPES. There is nothing on the market that penetrates wood like CPES and it's epoxy base assures you that the treated wood will remain treated indefinitely. If the rotted area is reasonably dry and the wood is saturated with the CPES nothing more needs to be done.

Insect protection is another issue. Wood that has been soaked in CPES is highly resistant to insect or bacteria attack, and wood that has been attacked by insects should be treated with CPES to consolidate the damaged wood and to make the wood unappealing to the insects. Still, coating the whole house with CPES will not prevent insect infestation, because there are too many areas that insects can get at that the CPES will never reach. CPES would help, but again there is the cost issue. Preventative measures (get the wood off the ground on stone or concrete foundations, treat the ground around the home with pesticides if it is a known termite area, etc.) and constant vigilance is the way to go. Some insects are more annoying than damaging, and those you just have to fight.

So, the bottom line here is protect what you can at construction time and then keep a good eye out for rot and deterioration. All log end should be CPES-soaked after the wood has dried, because they may rot if you don't. The normal wood preservatives don't work as well because they are petro-based and the bacteria eventually degrade petroleum mixes. This can never happen with an epoxy.

If you have more questions come back, and we'll be happy to try and answer them.