What kind of maintenance do you need on a log cabin? You don’t need much if you are only looking to keep the structure for a generation.

If a wooden structure is left to the elements for 25 years (one generation), nature will rot the logs in places and start the slow process of rotting the wood, especially in the areas where water is allowed to seep into the grain of the wood.

This is a view of bore damage after power washing.

Some of the most vulnerable areas for water seepage and rot are the ends of the wood and logs. The grain that is exposed at the end will suck up any moisture through capillary action and suck into cells deep inside the wood.

Water and organic material in the wood cells creates a perfect place for aerobic and anaerobic action that will rot wood cells. Other sets of problems that can destroy wood products are: worms, beetles, bores, birds, and mammals all can also degrade wood products.

As you inspect the wood products on your walls of your home, check for damage such as holes, sawdust on the floor or ground, or gnaw marks on the exterior and interior of structure. Holes as small as 1/8th-inch or as large as 4 inches can appear in the wood quicker than expected if not inspected frequently.

Bores are tiny, beetle-like insects that chew into wood products and are about 1/8th-inch in diameter. These beetles leave piles of sawdust behind from the holes they drill.

Most of the bores will enter coniferous logs through the bark or on cut lumber even without bark, but the bark seems to invite the bores. As the bores enter the wood they leave small piles of sawdust under their little tunnels.

The beatles or bores that make the holes will continue to damage the wood if there is nothing done to stop them. The product that was found by the forestry department is called “BORITE” (brand name) and it did stop the bore problem in the pine logs. There are probably other products that work as well but BORITE worked.

The next thing that needs to be addressed is the moisture. As discussed earlier, it is important to keep the water out of the cells of the wood to deter the rot in wood. The logs were power-washed, knocking the bark off the logs before the pesticide is applied.

Forest Products Laboratories, in Madison, Wisc., has been doing research on wood and wood products for many years. They have tested everything that might protect wood and keep it from deteriorating (paint, oils, and polymers), and have developed and revised a formula to protect wood products.

Bob Brennecke

The materials that are used are environmentally safe, easy to obtain, and easy to mix and use. Forest Products’s original formula was published in a pamphlet I since lost years ago but when they were contacted they were happy to help with the problem.

The materials used to keep water in check are: mineral spirits, paraffin, turpentine, and oil-based varnish. The mineral spirits, turpentine and the varnish are heated in a double boiler and the paraffin is then added.

The exact formula needs to be researched but I know after applying, the water beads on the wood for years. A garden sprayer works well for applying the waterproofing. Concentrate on the end grain of the logs and observe how the product sucks onto the ends of the wood.

The original formula was made with boiled linseed oil. After about 5 years, the waterproofing started to darken or turn black from mildew. Mark Knaebe, a natural resources specialist with the U.S. Forest Service, said TWP 100 series (Total Wood Preservative) is also a good product.

“If you have linseed oil without a good mildewcide, you will always get mold, even if you don’t use any next time,” said Knaebe. “Mildew will mine for the oil deeper down forever. If you had used a gloss varnish (as an ingredient, 20%) instead of linseed or other natural oil, there would be much less mildew.

“Pigments, in addition to adding some color and protecting the wood, they also protect the mildewcide so even 3-Iodo-2-propynyl N-butylcarbamate will have a short life without pigments. I’d add black pigment and a charcoal color. You may never have to coat again. If you don’t like charcoal grey or black, use TWP 101.”

The change to an oil-based varnish from linseed oil is supposed to keep the darkening from happening. A bleach solution was applied to the darkened logs to kill mildew, then flushed with water and allowed to dry before the solution of (paraffin, mineral spirits and oil based varnish) was applied.

A reapplication of waterproofing might be necessary every 5 to 8 years but if so, it sprays on quickly and is relatively cheap.

(Bob Brennecke lives in Ballwin, Mo., and can be reached at robertbrennecke@hotmail.com.)