There really is no best wood for a log home
By Jim Cooper
A sure way to enliven a gathering of log-home enthusiast the superiority of inferiority of a particular species of wood. It’s like tossing a gauntlet into a gathering of knights. You’re almost guaranteed that someone will rise to your challenge. Wood species provokes probably more heated discussion than any other aspect of log homes.
Log-home shoppers often come to me with glazed looks pleading for help deciphering the mountains of fact, fiction and fantasy surrounding wood species. Often they think they can spare themselves confusion by asking, “Which is the best wood for a log home?” Actually, that’s when things get complicated.
Recently, I spoke with two log-home company presidents who offer logs made from the same premium wood species. One was aggravated that some people in the log-home industry failed to acknowledge the superiority of his product. The other, who offered the same species, called it “vastly over-rated.” If industry experts can’t agree, how can a log-home shopper possibly hope for a definitive answer? Is there a definitive answer?
The difficulty of answering the question starts with the question itself. “Which wood is best?” Well, what exactly do we mean by best? Is it the strongest wood? The one with the highest R-value? The greatest thermal mass? The most decay resistance? The greatest insect resistance? The least expensive? The one that shows the least shrinkage, or the least checking or warping? And what about beauty? Most homeowners plan to look at those log walls for a long time, so appearance is no small factor. Each of these criteria really represents an independent question and plays an important role in determining which wood is “best.”
Take strength, for example. It’s easy to examine a table comparing the strength of various woods and pick the superior one. But is that the best wood? Maybe, but only if strength is the sole criterion. Log-home shoppers usually have more than one characteristic in mind when they ask which wood is best. To further complicate the issue, shoppers don’t always agree in which characteristics should be considered and don’t assign the same priority to the characteristics they list.
Consider another characteristic: R-value. Again, it’s easy to find the wood species with the highest R-value by looking at a chart. If R-value is our only interest in choosing a wood species, the chart answers our question. But what if we’re interested in strength based on a table, then we look for that wood in a table of R-values. We find the strongest wood is nowhere near the best in terms of R-value. If we choose the wood with the best R-value, it’s nowhere near the strongest. At this point, we have to choose which is more important to us: strength or R-value.
Maybe introducing a third characteristic will help sort things out. So, let’s consider decay resistance. Using the Wood Handbook: Wood As An Engineering Material issues by the I.S. Forest Products Laboratory, we search for the most decay-resistance species. We find that in the matter of decay resistance, the handbook groups woods into categories of “highly,” “moderately” and “somewhat.” Most of the 26 or so species of wood used for log building rank as highly or moderately decay resistant, so that the table is of limited help in settling disputes between individual species.
With decay resistance, we introduce another aspect of the argument. How will the house be built and maintained? Is it going to be left natural or treated with some preservative? Will the wood be in contact with the soil or isolated from it? Will the house be built to allow water to stand on the wood, or will it be built to protect the logs from prolonged exposure to moisture?
No log-home company that I am aware of recommends leaving exposed wood untreated. Thus, any wood will likely receive a treatment to prevent decay. Accepted building techniques require that wood be protected from prolonged contact with water. This means including roof overhangs and elevating wood above ground level. Often these techniques are mandated by building code.
Treating logs and trim and using proper building techniques reduces differences in decay resistance between wood species. With proper treatment and proper construction methods, any species can be considered highly resistant.
The same applies in the area of insect resistance. There is no wood used in log homes that is insect proof. Among woods, these are varying amounts of insect resistance, but any type is susceptible to certain insects. To prevent insect infestation, virtually all log homes receive some type of insect treatment. The treatment becomes the basis for insect resistance, making all woods effectively “highly” insect resistant — as long as the treatment is applied correctly and at proper intervals.
Let’s move on to another characteristic: shrinkage. Wood species vary in the amount they shrink, but all are subject to some shrinkage. Shrinkage is important because it plays a role in settlement. This in turn affects how a log house should be designed and built. The construction techniques used to accommodate 1 inch of settlement in an 8-foot wall are the same as those used to accommodate 3 inches. Because shrinkage and settlement vary not only between wood species, but between individual logs as well, most systems are designed to accommodate shrinkage within a range. It doesn’t matter whether the logs settle more or less. It is important that the house be designed and built to handle whatever amount takes place.
Finally, we can look at characteristics that affect appearance, like checking and knots. Normally, these don’t affect the strength or energy efficiency of a log wall, so their concern is mostly aesthetic.
Beauty is truly in the eye of the beholder. One person’s idea of rustic may be far from another’s. My own home has been judged rustic and contemporary by different people in the same day! So here, a table of values ranking wood as more or less knotty or likely to check has little meaning. Your personal taste is the judge.
By now you’ve probably gathered that I’m not going to name a “best” wood for a log home. Even though I favor and sell certain species of woods and have my own personal preferences, I recognize that when someone asks me which wood is best they are really asking not one but a dozen questions. The only fair reply is to give them a dozen answers and let them sort out which is most important to them.
Since many people find little comfort in that response, I’ve developed a more comprehensive answer. Every wood being used by log-home companies today is capable of producing a house that will give pleasure to its owners throughout their lives. Every wood used is also capable of producing a house that will be a source of aggravation and disappointment.
To ensure a lifetime of enjoyment, choose the wood and building system that give the style and appearance you want. Then make sure that construction follows the manufacturer’s instruction precisely, and pay careful attention to proper maintenance. If you do those things, you will find that you have chosen the best wood for your home.
Jim Cooper is the author of Log Homes Made Easy and the Log Homes Made Easy Log Home Project Planner