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A log home (or log house) is technically the same thing as a log cabin, a house typically made from logs that have not been milled into conventional lumber. The term log home is contemporary and preferred by most log home builders, while log cabin indicates a smaller, more rustic, log house, such as a hunting cabin in the woods.
Types of log homes Edit
There are two kinds of log homes:
Handcrafted log homes have been built for centuries in Scandinavia, Russia and Eastern Europe. These were typically built using only an axe and knife. The Scandinavian settlers of New Sweden brought the craft to North America in the early 1700s, where it was quickly adopted by other colonists and Native Americans. Possibly the oldest surviving log house in the United States is the C. A. Nothnagle Log House (ca. 1640) in New Jersey.
In the 1920s, the first milled log houses appeared on the market, using logs that were precut and shaped, rather than hand-hewn. Many log homes today are of milled variety mostly because they require less labor intensive field work than with handcrafted. There are perhaps 500 companies in North America that build the handcrafted, scribe-fit, style of log home.
Logs in log homes have varying degrees of moisture content. Any log will have moisture in it when it is freshly cut. In the case of "handcrafted" logs this moisture will naturally leave the timber, drying it out until it stabilizes with the climate it is in. This drying out causes movement and shrinkage of log diameters. As logs and timbers dry, the differential shrinkage (radial versus tangential) causes small cracks, also known as "checks," to open slowly over time. Checking is a natural occurrence for both air-dried and kiln-dried logs. This occurs in all log homes, regardless of construction method or how the timbers are allowed to dry and is considered normal as well as part of the charm of owning a log home.
Milled logs are processed in a different manner than handcrafted logs. Logs destined to become milled logs can become one of several types depending on the desired quality and end result.
Green logs Edit
Logs that are cut from the forest, brought to a mill or to a log home construction yard, bark removed, and then used to build the log home shell (handcrafted log homes), or sent through profiling machines (manufactured logs) are usually referred to as "green" logs if they have not been air-dried or kiln-dried. "Green" does not refer to color, it refers to moisture content (MC). The actual moisture content of "green" logs varies considerably with species of tree (cedar, fir, spruce, pine, etc), season in which it was cut down, and whether sapwood or heartwood is being measured. Green logs may have a moisture content between about 20% and 90% (oven-dry method of measuring MC).
One type of air-dried log is "dead standing," which refers to trees that have died from a natural cause (bug kill, virus, fire, or etc), and then were cut down after they died. Standing dead trees may be cut down 1 month after they died, or decades after they died, and so the term "dead standing" does not necessarily mean the logs have been dried down to Equilibrium Moisture Content. Dead standing logs can therefore be green, or they can be more-or-less dry.
After construction, green logs dry in service in the log building. Within about 4 years, green logs that are part of a completed log home come to equilibrium with their local conditions and have a moisture content of between 6% and 12% (known as Equilibrium Moisture Content, EMC). The actual EMC varies with local climate, season of the year, and geographic location.
Air-dried logs Edit
Some log home companies let the fresh cut logs or milled timbers sit outside in the open air to dry naturally. The timbers can be stacked with spacers (stickers) between them. This process allows the moisture content of the logs to naturally come down as the timber dries. This process requires at least one year per inch of thickness, and requires adequate space to let air circulate. If the logs are to be dried to an equilibrium with the local climate the process may take several years, depending on the location and size of timbers. In some environments the logs must be kept under some type of roof or cover so that rain does not affect the logs.
Once the logs have dried for the desired time frame the logs are profiled and shipped to a customer. Profiling usually does not take place until right before shipment to ensure that the logs stay as uniform as possible. Arguably this process may or may not have any benefit depending on many factors such as, local climate, species of wood size of wood, size of wood, and final location of the log structure.
Kiln-dried logs Edit
Mills that have a kiln on-site have the option of artificially accelerating the drying process. Green timber is placed inside a large oven where heat removes moisture from the logs. They can suffer severe checking and cracking if the kiln controls are not properly monitored during the drying process. Use of a kiln can reduce the dry time required by the manufacturer in order for production, from many months to a number of weeks. Kiln drying usually results in an average moisture content of 18-20%, average being the mean moisture content of the outside of the log and the center of the log.
Since logs reach equilibrium moisture content when they are between about 6% and 12% (in North America), and since most kiln-dried logs are dried down to about 18% to 20% moisture content, kiln-dried logs can be expected shrink and settle over time, but to a lesser extent than green logs. Common varieties of softwood lumber, such as framing lumber are dried to a somewhat higher moisture content.
Glue-laminated timber Edit
"Laminated" or "engineered" logs are a quite different approach to log home building. Full trees or, alternatively, sawn cants, are brought to a mill equipped with a dry kiln, the bark is removed and the trees are sawn into boards usually no thicker than two inches thick. These boards are then taken to the dry kiln where because of their size they can be dried without causing severe damage to the wood. Timber destined for glue lamination must be brought down below 15% moisture before the lamination process will even work so typically these timbers are dried to around 8-10% moisture. The drying process varies on the species of lumber but can be done in as little as a week. Once the drying process is complete the planks are sent through a surfacer or planer which makes the face of the lumber perfectly smooth. These planks travel to a machine which then spreads a special glue on the interior boards. Depending on the type of glue and type of mill there are two ways to finish the lamination process, one type of glue reacts with radio frequency to cure the glue in a matter of minutes and the other uses a high pressure clamp which holds the newly reassembled timbers under pressure for 24 hours. Once the glue has dried the end result is what is called a "log cant" that is slightly larger than the buyers desired profile. These log cants are run through a profiler and the end result is a log that is perfectly straight and uniform.
Some mills are capable of joining together quite small timbers by using a combination of face and edge gluing as well as a process known as finger jointing. These boards which would be scrap to any other mill could be used in the center of a laminated log or beam to bring waste to a minimum.
Types of milled logs Edit
Milled log homes have an assortment of profiles that are usually picked by the end customer. Just about every profiled log on the market today features an integral tongue and groove milled into the top and bottom of the log that aids in stacking as well as eliminates the need for chinking.
Methods of log home construction Edit
Scandinavian Full-Scribe, also known as the "chinkless" method, means naturally-shaped, and smoothly peeled (draw-knifed) logs that are scribed and custom-fitted to one another. They are notched where they overlap at the corners. There are several ways to notch the logs.
Corner styles Edit
Other methods Edit
Settling of log homes Edit
Once fabricated and assembled, the shell of the log home can be disassembled and the parts shipped to the final building site. This allows for centralized manufacturing of the home and relatively quick construction at the final site. Full-scribe-fit handcrafted log construction is a method of precisely marking where to cut each individual wall log so as to provide an extremely tight fits between naturally-shaped logs along their entire length and in the corners. A high degree of craftsmanship is required for success in this method, and the resulting tight fits of naturally-shaped logs have an esthetic appeal to many people.
Log homes that settle require such things as slip joints over all the window and door openings, adjustable jacks under any vertical element such as columns and staircases which must periodically be adjusted as the building settles, allowances in plumbing, wiring, and ducting runs, and fasteners for the walls themselves to prevent uplift.