The Rot Doctor


Subject: Rotten Beams
Date: Mon, 05 Jul 1999

I have an old post and beam house built in the early 1800s. I have two beams 8" x 8" x 25' long that have been attacked by some sort of wood borer (The holes are too small to be carpenter ants.) The insects are gone but the beams have rotten, penetrated about 1" to 2" on all sides. Some of the rotten wood has come off leaving gaping holes. I would like to know what products I should buy and how much of each would be required to fix the beams. Thank you.



Our CPES (Clear Penetrating Epoxy Sealer) is what you need. Assuming that the wood is reasonably dry, the application on all exposed surfaces should be sufficient. The insect holes will act as pathways for the CPES to get into the wood. The application by brush on the top and sides and into any seams should not be too big a problem. The bottom can be difficult, and often spraying is the best solution here. This would need to be done with a venturi-type air sprayer. We sell some small units, although for beams this size you might want to consider buying or renting your own electric model. You could, of course, spray all sides. Clean-up of equipment during and after use is with xylene, or our Epoxy Solvent.

I would make the CPES application twice. The second application will take much less CPES than the first, but will act to fill in the small holes and cracks. Following that you will need to fill gaps, crevices etc. with an epoxy filler. We sell Fill-It Epoxy Filler, which is great stuff but does dry just off-white, which may not be appropriate for your beams. An alternative is to make your own paste using our Layup & Laminating Resin and adding sawdust. The sawdust will give it a beige color, which may be okay, or you can subsequently add dry painter's pigments (burnt umber and maybe a bit of yellow) for a deeper color. It's all in the eye of the beholder. Both of these products bond at the molecular level with the CPES-treated wood to create a solid structure.

That should do it for you. I don't think I would worry too much about all the tiny insect holes, because the epoxy in the CPES will take care of most of those, filling them and adding strength to the wood.

As for quantity, I would guess that you're going to need at least one 2-gallon unit of the CPES. Maybe more -- it all depends on how much the wood absorbs, because you do want to allow the wood to absorb all that it will. You could start with 2 gallons and then if you see that it's not going to be enough, re-order immediately. As for filler or Layup & Laminating Resin, that is strictly a volume issue. You just have to look and make an estimate on how much in the way of voids you have to fill.