The Rot Doctor


Subject: Sealing frame wall & sheathing to slab
Date: Fri, 25 Jun 1999

I came across a reference to your website and products on the newsgroup. After browsing through the web information it looks like CPES can help with one of my projects.

We recently had a 20' x 20' two story barn style work shop and storage shed built. It's on a concrete slab with 2x4 frame construction and T-111 siding. Some sort of construction adhesive was supposedly use on the (pressure treated) plate, but I can't see any evidence of it. Water has come under the plate during some recent rain storms, I'm finding bugs running around inside, and I can see light under the wall at night is some places. I'm in the process of wiring and insulating the shop portion of the building, and cans see some gaps between the siding and the plate. The siding was painted with 2 coats of sprayed on latex house paint, but I don't see signs of the paint on the bottom edge of the siding. I could call the builder to come back and fix this up, but figure his subcontractors are just going to band-aid the situation, meaning that I'll end up redoing it sooner or later anyhow.

OK, so I want to seal the bottom of the siding and then fill in the narrow gaps between the siding and the plate and the slab. CPES sounds like a good bet for the first part of this. One question is whether there are any caveats WRT the pressure treated wood in the plate or the concrete slab. Based on my reading I'm guessing it should be OK. Second question is how much CPES it might take to treat the 80' perimeter of the siding and the partly exposed corner of the plate, with some slopover onto the slab. I assume a small roller would be a good way to apply this stuff.

To treat just the bottom edge of the siding with one coat of CPES should take about 2 quarts. I would soak the siding twice, so about 3-4 quarts. The second coat will absorb much less. There is no problem applying CPES to concrete or pressure treated wood.

Next, for the gap filling/sealing I have looked at the different caulks and fillers and related stuff at the building supply joints (Home Despot and Lowe's mostly) and nothing really stands out. I noticed in the Q&A area a recommendation to use polyurethane rather than silicone latex. How about non-silicone latex caulks, or butyl rubber caulks? How about those nasty sticky foaming polyurethane filler/caulks that come in the pressurized cans? I'm not familiar with the 3-M 4200 or 5200 sealants that were suggested (from the marine supply houses) so will do a bit of research on them. Any other thoughts for this job would be welcome.

The silicone caulks don't seem to stick to well, the non-silicone latex caulks don't last. In a few years you are back digging it out and replacing it. The foaming polyurethane I haven't had too much personal experience with, but the applications that I've seen don't seem to have much flexibility. 3M 5200 and 4200 are polyurethane products that are designed for the marine environment. They are primarily used on the seams or gaps between the planks of wooden boats. They bond very well (the 5200 is a "permanent" bond, the 4200 is a "removable" bond) and have the flexibility that wooden boats need. In the marine environment they have a life expectancy of 20 years. At $12.00 for a 10 ounce cartridge it is a little more expensive than other products, but if you don't have to think about it for 20 years, it is money well spent for me. Make sure that the surfaces you are bonding to are not oily.

Thanks, Al

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