The Rot Doctor


Subject: house sill beam repair
Date: Thu, 11 Jul 2002


Questions about amounts and types of product:

Problem is 6' section of sill beam in 100 yr old house - bought house with localized carpenter ant problem and earth up onto siding in same spot (surprise). This is same spot where some mysterious work had been done involving removal of a few inches of sill beam outer surface. Last year killed ants and changed grading so that foundation is exposed - therefore the wood is now pest-free and dry. Have access to outside and most of top of beam, but access to inside of beam would be problematic.

2 ft section is seriously rotted - only top few inches of a 6 x 6" is intact and the rest is dry one-inch chunks of wood falling out. Problem tapers away until only the bottom 1 inch is rotten and flaky. Ant tunnels do not appear extensive in this area. Structurally, we have one stud of a two-story house sitting on almost nothing -but there's no indication of movement, so far.

Plan is to buy CPES, L&L resin, and some epoxy filler. Will get syringe kit and sawdust.

Since you have good access to the top and will therefore be able to drill 3/8" (or larger) access holes, I don't think you will need the syringe kit. CPES can be applied easily to these areas with a turkey baster, and so can the Layup & Laminating Resin by popping off the bulb and pouring in the mixed resin.

Will use pressure treated wood as dutchman fill in the large area.

Well, okay, if you want...but it is our personal opinion that untreated wood doused with CPES (after cutting and trimming) produces a more permanent rot-protected dutchman. The quality of pressure treated wood varies considerably...some is okay and some is not. The petro-based chemistry used in some of the pressure-treated wood will interfere somewhat with the penetration of CPES.

How much quantity of products?

For the CPES, I would estimate two of the 2-quart units of CPES, unless you plan to spray other undamaged areas of the beam for future protection, in which case we would suggest the 2-gallon unit.

The amount of the Layup & Laminating Resin you will need is more problematic, since you can't really know how much there is to fill inside the beam, or how much you may lose through leakage. I would suggest at least two of the 2-quart L&L units, and, again, to be sure you may want to order the 2-gallon unit of the resin. I can't imagine that you would use more than 2 gallons. You will also be using the L&L Resin mixed with sawdust into a putty mix for closing access holes and for the possible fill of any remaining gaps/cracks/holes. This will serve the same purpose as our Fill-It Epoxy Filler and save you having to buy three items.

Use lacquer-thinner for cleanup and equipment flushing.

How many drill holes per square foot (as seen from the top?) - do I use these for both CPES and L& L?

We would suggest staggered holes drilled every 4-5 inches. More are okay if you think they would help. Drilling can be to approximately 1/2 way through the timber, or, all the way until soft wood is encountered. And yes, they would be used for the introduction of both the CPES and the L&L resin. However, the CPES should be generously brush/spray applied to all accessible surfaces as well, allowing the wood to absorb all that it will.

Since the bottom of the sill beam is rotted, you're going to quickly start to lose CPES into the ground. However, it will also penetrate horizontally into the deteriorated wood. So, we suggest doing a deep flood of the drilled holes initially, that is, filling them completely several times in a row to allow lateral migration of the CPES into the bad wood before the excess is lost into the ground. Losing the CPES into the ground isn't going to do any harm, though, since it will impregnate the dirt with epoxy and make it very unattractive to insects, fungi and bacteria.

Website suggests wrapping in kitchen wrap to prevent L&L from flowing out -yet the worse parts are underneath - how can I wrap that?

You are going to wait for at least several days (or longer) after the application of the CPES before you begin infusion of the L&L Resin, and to some extent the CPES will help seal off the ground. We'd suggest making the first infusion of the L&L Resin a fairly light one, so that it drops down and builds a bottom layer. This will cure hard in 24 hours and should then provide a base for the application of the rest of the resin.

When you wrap the sides of the beam with the kitchen-wrap and pour in the resin, you should see within 10-15 minutes some indication that the resin is flowing to the sides. If not, then you can assume you are losing resin somewhere. If the inside of the beam has cracks/holes or is porous, then that would be a place for resin leakage.

An slight alternative here, if you suspect that you might lose resin on the inside of the beam, is to make your first L&L Resin application one that has the fine sawdust mixed in with it to add bulk. The mix should be pourable, and allowed to settle down, cure (24 hours), and then you can proceed with the rest of the fill. These are conditions we often face in marine reconstruction, so one has to be intuitive -- kind of like a dentist drilling into a bad tooth.

If the weather is hot during this process the L&L Resin will tend to cure much more quickly. We suggest mixing the resin at 70's temperatures and getting it into the wood as quickly as possible. In hot weather we often pour early in the morning when temperatures are a little cooler.

Can I spray CPES with cheapo plastic spray bottles that are disposed of afterwards?

Yes, as long as the bottles are intended for insecticides, that is, from the garden-area of the local home store.

We're architect & engineer and are aware that we need to stabilize this, but will be looking for practical cost- effective ways for this test project.



Good analysis! Good questions! It's a kind of tedious process, but the result is a VERY hard and structurally sound repair. Once done, the repair will be virtually indestructible.

Come on back if you have additional questions.