Exterior Log Home Care

- Surface treatments should include borate -

Summary: Insects and rot fungi will attack the exterior of log homes if it is not protected. An application of borate wood preservative, which controls both insects and fungi, plus some type of exterior sealer is all that is generally needed.

Jack DeAngelis, PhD

OSU Ext. Entomologist (ret.)

Log homes need special exterior treatments that conventionally-built homes do not. Logs are prone to attack by rot fungi and a variety of insects that will damage the surface if steps are not taken to prevent infestation. Fortunately treatments to prevent this damage are relatively inexpensive if done during construction and before water sealant finishes are applied.

Borates stop wood damage

There are a number of manufacturers that supply products to protect log homes from wood destroying insects and fungi. Many of these products are based on insecticidal borates. Bora-Care (Nisus Corporation) and Shell-Guard (Perma-Chink Systems) are popular glycol-based** borate products used to treat unfinished log homes (see Bora Care Wood Preservative).

Timbor, also from Nisus Corporation, is a pure borate powder without any glycol additive and is mixed with water to apply. Some studies indicate that the glycol in Bora-Care/Shell-Guard helps to carry the borate into the wood, but other studies found no advantage from the addition of glycol (see Timbor Wood Preservative).

Logs being prepared for building. Photo by William M. Ciesla, Forest Health Management International, Bugwood.org

All borate products should be applied before wood is stained and sealed for best results. Bora-Care is a 40% solution whereas Shell-Guard is a 25.3% solution. Keep this difference in mind when comparing costs. Timbor is somewhat cheaper than either of the glycol-based borates but does not have the possible benefits of the glycol penetrant. All borates are water soluble so wood must be stained or painted to seal the surface following treatment.

Bora-Care and other borate-based wood preservatives are available here, but are not generally available in home and garden stores.

Fused borate

Another form of borate that is useful against rot fungi and insect pests is called fused borate. Fused borate is a solid rod of borate or borate/copper mixture that is implanted in a wooden timber or log. Fused borate is commonly used in utility poles. Moisture in the wood releases the preservatives which diffuse into the wood fibers. Two popular fused borate products are Impel Rods and Cobra Rods. Fused borate can be used when treating finished woods and log ends.

Jack DeAngelis, Ph.D.

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