Wood Species and Characteristics
At Avalon Log Homes we offer several different styles of logs, including milled handcrafted and half-log siding. We most typically use standing dead timber that has been harvested high in the Rockies. This means that our logs have already been dried by Mother Nature. We predominantly use Douglas fir, Engelman spruce and lodge pole pine. Our logs are approximately 19% moisture content. This low moisture content greatly reduces checking (cracking) and settling. It is unlikely that our logs will develop unexpected twisting and deformities. Our wall log diameters measure 6", 7", 8", 9", 10", and 12" (other diameters available upon request). We also offer milled or handcrafted beam length logs available for purlins, trusses, porch posts, and other such uses.
Following is a brief discussion about logs:
Wood Species and Characteristics
as written in the ILBA Land to Lock up Manual
The log home: by definition, logs are the single most predominant characteristic of these log homes, and the very reason builders and owners alike, are drawn to this form of construction. What could be more natural? The appeal of logs is apparent to all log homebuilders and owners. Visitors to log structures are immediately drawn to touch the logs, soothed by their strength and character. (How often do you see people caress drywall?)
The longevity and strength of logs is evidenced in the well-built log structures of Norway and Russia, which are still standing proud and true after more than 800 years. The integrity of the structural design is essential to a long-lived legacy, and a careful look at structural components is critical. The choice of what logs to use is also an important consideration, and it is worth understanding the differences and characteristics of various species.
Different building styles can dictate what types of logs are used. Handcrafted log homebuilders select logs based on an extensive list of characteristics. Different species may be superior for certain joinery techniques, building design, and structural performance. Geographic location (where the logs are going to, or where they are coming from) might also be a consideration in wood selection. Weight bearing logs such as wall logs, floor joists, roof rafters, purlins and truss components usually require engineering and some species are better suited for these structural requirements.
The log builder, presented with the task of selecting appropriate wood for a project, needs to consider what lengths are required, what the average mid-span diameter is, what is the amount of taper the logs have and what maximum butt size and minimum top size are acceptable.
Midspan size of log diameter will contribute to the thermal performance; the larger the log, the greater the "R" value attributed to it, based on formulations attributed to various species of wood. Depending on climatic requirements and local building regulations, a minimum log diameter will be required. Based on an average R 1.5 per inch of log diameter, coupled with the extent and integrity of joinery between the log surfaces, a minimum 10" log is an acceptable norm for log diameters in colder climates. One might, however, use logs of smaller diameter if the purpose of the building is, for example, a summer cottage.
No matter how dry the logs are, all log structures must be built to accommodate shrinkage and settling. Whether building with seasoned wood, dead standing, green, winter cut, or kiln dried, a knowledgeable log builder builds according to moisture content, anticipation and allowing for movement in response to the drying and seasoning process with allocations for shrinkage and settling of logs. As wood fiber loses moisture, cell walls shrink and collapse, which can reduce the overall diameter of a log by as much as 6%. This factor, accumulated over the finished height of a log wall, as well as through door and window openings and structural support points, must be accommodated.
Moisture gain and loss can also be affected by roof overhangs, proper elevation from grade, and treatment to the wood surfaces with effective stains and preservatives. Controlling moisture content of the logs is important. A surface stain or preservative must allow the logs to breath and expel excess moisture; otherwise an environment for rot and decay is created. In some very arid areas, humidity should be introduced into a log home in order to stabilize wood fibers as well as to slow down the drying process and avoid radical checking.
In cold climates, logs react differently during the seasonal changes. Warm interior log walls may dry out. Meanwhile the outside surfaces remain frozen and do not continue losing moisture until the hot summer sun beats down. Unless the log building is constructed from dead standing or kiln dried logs, this see-saw process of moisture balancing can continue for a number of years before the wood stabilizes.
Most handcrafted log builders prefer to work with green wood, preferably winter-cut (when the sap is still down in the roots). Green logs are more easily crafted and a skilled builder will calculate moisture loss and its effects and will build to compensate for shrinkage and settling.
Since seasoned fire-killed, kiln-dried, or dead-standing timber is more difficult for handcrafters to work with, it is often preferred for use in chinked log wall structures where less work is required on the laterals. Dead standing and kiln-dried wood can also be used in full scribe work. While "dry" wood does settle less it will still lose moisture and the log builder must anticipate and build accordingly.
"A rose by any other name is still a rose." One of the greatest discussions between builders, and perhaps, one of the questions we are most frequently asked by our clients; is what species of wood should be used. Cost plays a role in choosing wood species, but it is not the most important factor, since all species have their own desirable traits.
Geographic location and forest ecosystem bear the greatest influence on log selection. Primarily softwoods are chosen due to their superior "R" factor, ease of handling, straightness of grain, and availability. Cedars, Pine, Spruce, Fir, and Larch are all commonly used as building logs, and each has different qualities. Western Red Cedar contains turpentine's within its resins thus rendering it more rot resistant, and it does not check or shrink as drastically as other species. Douglas fir is heralded for its superior density, if it lacks in simple "R" value, it is made up for in structural performance. Spruce is valued for its light color, and while it may not match the qualities of Douglas fir for structural loading, it is none the less an excellent choice of building log.