Today's Homeowner

By James Dulley

Creators Syndicate

Dear James: We are building a room addition to our house. We have had termite damage in the past, so we want to treat all the lumber ourselves, if possible. Are spray-on borate chemicals a good choice? — John Z.

Dear John: There is nothing more frustrating than to poke at a blemish on wood trim, only to push all the way through to a gaping cavity. That is when you know that the termites or carpenter ants have been having a feast at your expense. Once a house or addition is complete, it is virtually impossible to get access to properly treat all the wood surfaces.

Pretreating all the lumber with borate chemicals is probably your best option. Borate chemicals protect the lumber from termites, carpenter ants, old-house borers, beetles, silverfish, cockroaches, etc. and also from brown and white fungi and wet rot, which can slowly cause the wood to deteriorate.

The advantages of treating lumber with borate chemicals, as opposed to other professionally applied chemicals, is that they are not highly toxic to people or mammals. Avoid getting excessive amounts of it on plants or in ponds with fish.

Once the wood is treated with borate chemicals and dries, the appearance of its surface is still similar to untreated lumber. You can still saw, nail and screw it exactly like untreated lumber. Borate chemicals will not corrode metal fasteners and they are reasonably priced.

Borate chemicals belong to a class of wood treatments that diffuse and actually penetrate deep into the wood surface as opposed to coating the surface like paint. It can penetrate up to an inch deep. When the insects chew on the wood, the borate blocks up their digestive tracts and they die. Many of the worker insects also carry the borate-treated wood fibers back to the nest.

Borate chemical solution can be applied by any standard method — brushing, spraying, flooding and immersing in a bath. Spraying, using a common hand pump sprayer, is probably the easiest and most effective application method for the do-it-yourself homeowner.

If you can find a long trough, immersing the lumber completely provides the deepest penetration of the borates. Leaving it immersed for about three to five minutes is usually long enough. Over a week or so, the borate chemicals will slowly penetrate even deeper to about a one-inch depth.

The simplicity of using borate chemicals to treat wood is also their primary drawback. Borate chemicals are typically sold as a powder that you dissolve in water and then apply by any of the above methods. Since it is water soluble, it can slowly leach back out of the lumber if it becomes damp. Over time, it will lose its insect and fungi-fighting properties.

It is imperative to treat all the surfaces of the lumber and especially the cut ends. Talk with your contractor about having the majority of the framing lumber delivered after part of the new room addition is protected from the rain. Treat all the ends of the lumber with borate at one time while the lumber is still strapped and bundled together.

As with all treatment methods, make sure the wood surface is clear of dirt, waxes, oils, mold and anything else that will block the borate solution from the pores in the wood.

Follow the manufacturer’s instructions for mixing the borate powder with water. Typically, one pound of borate powder is mixed with a gallon of water. One gallon of borate solution should treat about 200 square feet of lumber surface area. When spraying, as opposed to brushing, there is some waste so the coverage may be less.

Send your questions to Here’s How, 6906 Royalgreen Dr., Cincinnati, OH 45244 or visit