The Rot Doctor


Subject: large beam
Date: Sun, 31 Jan 1999

I am looking for a solution for a large problem. While doing restoration work in a 150 year old temple a belong to it was found that a large beam (approx 12" by 16" 30 foot long) has a rotten hole in it due to old water damage. It is in the upper structure that is near a dome. It seems replacing it would be near impossible due to the location and size. I am looking for not only a filler but a product to regain the strength. Any ideas??


Mark K.


The rot can be repaired with a combination of Clear Penetrating Epoxy Sealer (CPES) and Layup & Laminating Resin. The wood must be dry, and you will need to drill 1/4 inch or larger access holes to inject the CPES. These holes should be downward-facing so gravity is working for you. In addition, the CPES should be brushed on generously all over the surface where any deterioration appears. You should apply as much CPES as the wood will absorb. Allow at least a week, and probably 2 weeks, for the epoxy carrier solvents to evaporate away and the epoxy to cure.

Assuming that there are hollows inside the beam caused by the deterioration, you would now follow up by injecting (use a kitchen baster) Layup & Laminating Resin into the holes. Again, put in all the L&L Resin the wood will accept. Surface gaps and hollows can be filled by making a paste with the L&L Resin and sawdust. This will give you a final appearance that is not too intrusive. Make any surface application smooth, though, because it's almost impossible to sand after it cures. (NOTE: for a painted beam, our Fill-It epoxy putty could be used.)

What you have done now is replaced missing wood material with a premium epoxy. The L&L Resin bonds at the molecular level with the CPES-impregnated wood. The area will be highly resistant to rot and any kind of water damage. There is no real good answer, in terms of structural numbers, about the strength of the beam. Epoxy and wood is commonly used in boat construction, where strength is very important. My opinion is that if the beam is now showing no signs of breaking or sagging, then the epoxy solution is sufficient. In some cases, engineers have specified "sisters" on repaired areas, that is, attached outside additional support in wood or metal.

The repair I have outlined above have been used many times with the CPES and the L&L Resin. We have heard of no failures. Come back if I can answer additional questions.