What should I put on my log home to protect it?
Preserving and cleaning your log home is essential for longevity of your home. It’s imperative to understand the intimate connection between a building’s location & design and a coating’s performance. The location and design of a log building is a key contributing factor to long-term maintenance costs. This very important detail is too often overlooked. Different locations will frequently require different building designs. If the building is not properly designed for its location, then surface maintenance inevitably becomes a more regular task no matter what brand of exterior wood coating is used. And when a coating fails to live up to expectations because of location and design factors, it usually gets the full blame. The wood finish becomes an easy target because its breakdown is so obviously visible and is regarded as the cause of failure instead of a symptom of deeper underlying causes. A quality log home finish, although it will certainly perform better than the cheaper varieties, will never achieve its full performance potential when design considerations have been overlooked. A wood finish alone can never remedy design deficiencies, no matter how good it is! Nevertheless, the type of coating to use on a log home should possess the following characteristics:
- Exceptional Water Resistance - Shield the Wood Against the Sun’s Harmful Rays - Prevent Graying and Hold Color Longer - Discourage the Growth of Mold & Mildew - Protect Against the Abrasive Elements of Weather - Allow for Some Degree of Moisture Vapor Transfer - Have Minimal Impact on Air Quality
A Unique Challenge
Log homes pose a unique challenge, for any type of exterior wood coating because the mass and surface of a log will vary from log home to log home. Each individual log can contain varying moisture contents, differing amounts of resin, a predominance of bark, cambium, sapwood or heartwood surfaces, and different densities of growth rings. In addition, log products are skip-peeled, draw-knifed, finely milled or somewhere in between and also come in various sizes, shapes and profiles. And let’s not forget all of the numerous types of species of wood. Unfortunately, it’s not possible to design a log home coating that will wear in a similar manner over such a wide range of variables.
Prior to coating with a wood finish, a new log home normally requires a seasoning period to allow moisture within the logs to be released to the outside environment. The moisture content of a particular log building will vary from one manufacturer to the other, so it is best to consult with your log manufacturer for advice on when to first coat the exterior logs. Generally, it is recommended to wait a minimum of 6 months after the home has been built before applying the first coat. This allows the log’s surface to open up and dry which in turn makes a better surface for a wood finish to absorb into and bond to. To play it safe, apply only one coat of stain on your new home. If too much stain is prematurely applied, moisture-related coating problems such as mold, mildew, and peeling may occur. This initial single coat should provide adequate protection on the log walls for the first year. Normally another single or double coat will be necessary the following year.
Before coating, spray the logs with the bleach solution mentioned earlier and pressure wash clean at 500-750 psi. Additional surface preparation may be necessary on logs that contain mill-glaze, bark, cambium, or are altered by a draw-knife. On such logs, scuffing the surface with a non-ferrous wire brush or with medium to coarse grit sandpaper will help to insure a better performance of the coating.
Once the home has seasoned, the performance of subsequent coatings should improve considerably. The frequency of reapplications will depend on climate, location, extent to which surfaces are sheltered from weathering, nature of the wood, quality of the finish, and application techniques. If the logs are checking and cracking exposing untreated wood, or if the finish shows signs of wear and is not providing an adequate water barrier, it’s time to recoat. Also, the Southern and Western exposures absorb the full force of the elements more directly, so expect to recoat those areas more often.
Your Ends Are Special
Special attention should be given to exposed log ends. End grain absorbs twelve times more water than the rest of the log surface. If left unprotected, end grain is particularly susceptible to fungal attack. To prevent such an occurrence, periodic inspection and treatment of the log ends with a quality water-resistant finish is advised. In addition, waterproofing the end grain will significantly reduce checking of the log ends.
An Internal Dilemma
Many new log homeowners desire a transparent, cleanable surface on the inside log walls that only a varnish type coating can provide. Because varnishes are basically a clear paint that forms a film, it is important that the logs are adequately dry before applying such a coating. Otherwise, as previously discussed, moisture-related coating problems could occur. Since the amount of moisture in the logs will determine the length of time required to wait, it is best to consult the manufacturer of your logs for their recommendations regarding a time frame for applying an interior varnish. If any doubt, wait at least 6 months and through a heating season before coating the inside logs with a varnish. Never apply a varnish on the outside logs!!!
Check It Out
Another area of concern is the formation of cracks or checks in the logs. Although there is a variety of factors that cause checking, our concerns are checks caused by moisture. There are two sources of moisture that contribute to log surface checking:
- Internal - Environmental
Internal moisture is the water inherent in the tree when it is freshly cut. This water is located within the wood cells and in their cell walls. The moisture within the wood cell is known as free water and is the first to be eliminated in the drying or seasoning of the wood. Free water is eliminated when the logs have reached around 30 percent moisture content. All moisture located in the cell walls is known as bound water and does not begin to leave the wood until all the free water from the wood cells is eliminated. As the water in the wood drops below 30 percent moisture content, the release and elimination of bound water begins. It is during this stage that log shrinkage and checking occurs.
Ideally, in the “seasoning” stage, moisture in the logs should decrease at a steady, even rate. The more rapid the rate of moisture release, the greater the probability of checking. Consequently, a slower release of moisture will reduce checking and provide a more uniform shrinking and settling of the logs. Since numerous variables contribute to the rate and volume of moisture exchange from the logs to the environment, control of this natural process by the homeowner is best achieved by the maintenance procedures already discussed.
Environmental moisture is caused by moisture from the external surrounding environment such as snow, rain, lawn sprinklers, etc. As the wood surface becomes wet, it swells or expands, and as it dries, it contracts or shrinks. When the wood is subjected to a number of these wet and dry cycles, and in winter climates freeze/thaw cycles, the stresses that result cause cracks in the wood. All the precautions and methods mentioned earlier in relation to controlling fungi apply here. Once again, the whole object is to keep the logs dry. That is the reason it is so important to apply a good quality, water-resistant wood finish. Such a finish will provide the necessary water-repellency needed to minimize moisture-related cracks.
Finally, don’t overlook upward facing checks. They can be a nagging source of air and water infiltration. The wider and deeper they are, the greater the potential for problems. Sealing the checks with a caulking material will usually remedy the situation, but it’s a smart idea to saturate them first with a wood preservative before caulking. This precaution will greatly reduce any chance of rot. Before proceeding, contact your log home manufacturer for advice on the type of caulking to use and the best procedure to follow to properly accomplish the job.
This sections content was provided by The Continental Products Company.