The new section of the house had been built over a crawl space, and the crew was able to apply a borate product (Tim-bor) to the floor joists. The crew used the same treatment in the attic on the building’s original rafters that were infested with termites. On the exterior sill plates, where wood was damp, and on some damp floor joists, they applied another borate solution (
“We did the treatment a year and a half ago, and there’s no sign of new infestation or rot,” Ocampo says. “Our next project is one I’m really excited about. We’re going to treat all the wood at
Mission San Juan Capistrano.” One of the advantages of borate is that it allows homeowners to keep on top of termite infestations or incipient rot without having to use toxic substances. Borate is nonrestricted, which means anyone can use it.
It’s important to know which product to use and how to apply it. To treat an entire house, you’ll probably want to hire a trained operator who has the equipment and know-how to apply the product correctly. For a small infestation or a follow-up treatment, you could do the work yourself.
To halt damage from termites and wood rot, David Ocampo of South Shore Exterminating treated the floor joists of the Adobe with the borate product, Bora-Care.
If you find an infestation of termites in a door or windowsill, for instance, you could inject a concentrated borate gel (such as
JECTA) into small, pre-drilled holes. You don’t have to strip the paint first. The borate will diffuse under the paint film and begin protection immediately, even if the wood is wet. Gel is also good for protecting the bottoms of posts, which are subject more to rot than termites, as long as there’s no ground contact. Where to Use Borate
Let’s say the unpainted risers beneath the back porch steps show signs of wood rot. A glycol-borate mix might be the best bet. Checks and weathering in unpainted wood actually improve penetration. If the wood is wet to the core, the borate moves toward the moisture.
If you want to reduce the risk of swarming termites in your attic, you can have the attic rafters, joists, and sheathing treated. The same goes for basements. As long as the sill plates and band joists haven’t been painted, liquid borate will provide protection.
You can’t lose with borate because it’s relatively inexpensive. The cost is $95 to $120 per gallon, and you can treat about 800 board feet of wood, the equivalent of 150 2x4s, 8′ long, or the average amount of lumber in an unfinished basement.
If your house is built with balloon framing, you may be able to finesse a paint brush up into the wall cavity by working from the basement. The ideal is to protect all wood within 3′ of ground level. Even so, you should be able to brush or spray liquid borate on the band joists and mud sill. Outdoors, use a garden sprayer and treat the foundation wall and bottom of the siding. Don’t go overboard because borate is a nonselective herbicide and toxic to plants.
Borate has proved practical for spraying or brushing on heavy timbers in historic structures, from log buildings to totem poles. (Photo: Richard Sexton)
In a heavy-timber building, such as a log cabin, the volume of preservative required is greater than the surface spraying that will protect a normal home’s 2x framing. Treatments that can be brushed on or sprayed (Tim-bor,
PeneTreat, Armor-Guard, or Shell-Guard) are the least expensive option, but for maximum penetration of wood that is already showing signs of rot or infestation, you might be better off with the glycol-treatment. Glycol makes the borate soak into dry wood more effectively, and glycol seems to make logs more resistant to termites. This was the treatment the National Park Service chose for totem poles in Alaska. Initially it darkened the wood, but after a few days the glycol volatilized, and the wood returned to its normal color.
Because the ends of logs absorb moisture, it’s a good idea to provide an extra dose of medicine beyond brushing or spraying borate. Inserting rods made from concentrated, fused borate (
IMPEL Rods) will spread fungicide through the wood’s fibers when the moisture content rises above 30 percent the level at which decayed fungi become active. The borate protection remains in place even if the wood dries out, and it becomes active again if the moisture level rises.
With precautions, borate treatment can even protect wood in contact with the ground. The key is to provide an ongoing source of borate to replenish any that leaches out, to reduce or eliminate any source of oxygen (which is necessary for decay), and to protect the wood from water. One method is to paint gel on the surface of the post and wrap the post in plastic before putting it in the ground. The plastic cuts off the supply of oxygen and will retard wood rot even if water does reach the post. (Plastic made for this purpose is sold by borate suppliers.) Last, top the post with a zinc or copper cap to prevent water from entering.
Defeating Water Migration with Borate
Because borate follows moisture, it’s particularly effective against subterranean termites. The insects’ mud tubes are moist, and the borate goes right to them. The bad news is that if the wood dries out, the borate dries, and it rises to the wood’s surface where it can be washed off by rain. (It may also diffuse into the soil if there’s ground contact.) That’s why it’s important to keep the wood that you’ve treated from getting wet.
Ambient moisture isn’t a problem. Borate can go through unlimited cycles of wetting and drying as long as the moisture remains on the surface of the wood and isn’t washed off. In attics it should last indefinitely. Even log homes generally have enough of an overhang to prevent borate from washing away with rain, but if you treat a shake or shingle roof with borate, make sure to follow up with a water repellent. The water repellent and borate product must be compatible. Some glycol-containing products may keep the water repellent from drying properly. Check with suppliers before buying, or do a patch test. (Make sure to wait until the glycol is dry before you apply the repellent.)
The termite problem is so severe in the South and Hawaii that you’ll find the future of borate in borate-treated lumber. Two companies that make borate-treated lumber products have retooled nine of their 200 factories, but in the next few years the availability of these materials will spread. Advance Guard dimension lumber is treated with sodium borate, and SmartGuard sheathing, siding, and cellulose insulation is treated with zinc borate, a form of the salt that doesn’t diffuse as easily as others. This zinc borate also functions as a flame retardant. Costs run about 30 percent higher than comparable building products.
While you’re waiting for the new borate goodies, you can always resort to the old dip-treat method. Set up a section of gutter or a bathtub for the borate solution, then immerse the lumber for three to five minutes. Leave the wood soaking for a week, and the chemicals will penetrate 1 or more, but you’ll have to contend with warping or raised grain. If you’re making a repair after borate treatment, remember that borate is a salt, and for your carpentry to last with the wood, you must always use galvanized or stainless steel nails never aluminum or uncoated nails.