Log home
From Wikipedia, the free encyclopedia
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.
There are two kinds of log homes: "handcrafted" and "milled" (also called "machine-profiled"), made with a log house moulder. A handcrafted log home is typically made of logs that have been peeled but are otherwise essentially unchanged from their original natural appearance when they were trees. A milled or machine-profiled log home is one constructed of logs that have run through a manufacturing process to remove natural features and imperfections of the log and convert them into timbers that are consistent in size and appearance. Many handcrafted log builders do not consider milled logs a log at all, a position milled-log manufacturers disagree with.
Handcrafted log homes have been built for centuries in Scandinavia, Russia and Eastern Europe. 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. In the 1920s, the first milled log houses appeared on the market, using logs that were precut and shaped, rather than hand-hewn. Most log homes today are of milled variety mostly because they require less labor intensive field work and there are many more options available than with handcrafted alone.
One major factor that isn't always addressed is moisture content. Any timber from large to small will have moisture in it when it is fresh cut. Log homes of all types experience varying degrees of moisture content. 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 in the timber, as the timber dries the pores on the exterior of the wood seal up. The moisture in the center of the timber keeps trying to escape and eventually opens a crack in the timber. This crack also known as a "check" can continue all the way to the heart of the timber sometimes leaving quite a large crack on the side of the 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. The end quality of a milled log has a lot to do with it's moisture content at the time of construction..
- Green Timber*
Logs that are cut from the forest, brought to a mill, cut to a profile and sold quickly are usually referred to as "green" or "wet" logs. These logs will have a very high moisture content sometimes upward of 25%, which will cause massive shrinkage and cracking over a long period of time once the home is built.
- Air Dried Timber*
Some mill's elect to let the fresh cut logs sit outside in the open air to dry naturally. This process allows the moisture content of the logs to naturally come down as the timber dries. This process can take several months and requires the mill to have space to let the timber air out. 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. Air dried timber will settle much less than green timber however, it will check and crack just as green timber would.
- Kiln Dried Timber*
Mill's 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 much faster than mother nature. Once profiled, Kiln dried logs are even more stable with less shrinkage and settling than air dried timber. They can suffer severe checking and cracking if the moisture content is not properly monitored. Kiln Drying can cut down the dry time from many months to a number of weeks and usually results in an average moisture content of 18-20%.
- Glue Laminated Timber*
"Laminated" or "Engineered" logs are a quite different approach to log home building. Full trees 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.
The laminated or engineered log also has the least moisture content of any log on the market and since it's moisture content is below the natural shrinkage level it will not shrink, warp, or settle. Checking is to an absolute minimum and does not result in the large gaping cracks found in other log products.
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.
Milled logs in addition to being more consistent in size and appearance can be found with varying degrees of moisture content depending on the manufacturer and desired end quality of the milled log.
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[edit] Methods of Log Home construction
- Scandinavian Full-Scribe (also known as the "chinkless" method) where logs are scribed, custom fitted to one another, and notched where they overlap at the corners
- Flat-on-flat (logs are flattened on top and bottom and stacked)
- Milled log homes often are constructed with a Tongue and Groove system that helps to align one log to another as well as create a system for sealing out the elements.
[edit] Corner Styles
- Butt-and-Pass where unscribed or milled logs butt up against each other at the corners without notching
- Interlocking Saddle Notch - Normally seen on "D" or Full Round Profiles where a notch is cut into the top of one log and bottom of another, these two logs then interlock creating a tightly sealed corner.
- Dovetail - Typically seen on square or chink style logs. A special dovetail is cut on the end of a log where it would rest in the corner. One to the right, and one to the left. This also creates a nice tight interlocking corner.
[edit] Other Metholds
- Half-Log where the structure is built with conventional (non-log) techniques. Half-log siding is applied to the exterior to replicate the look of full-log construction, it can also be seen with false corners to give a more realistic appearance..
[edit] Types of Milled Logs
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.
- 'D' Shape Logs which are round in the outside and flat inside.
- Full round Logs which are fully round on the inside and out.
- Square Logs which are flat on both the inside and out and may be milled with a groove that could be chinked. When dealing with milled logs chinking is more of a personal preference and is not required to seal the home.
[edit] Fastening Systems
These are some methods for connecting the logs together keep in mind each manufacturer usually recommends their own way of sealing and securing their logs.
Spikes: Basically a large nail, usually spiral, driven into the logs nailing them together.
Lag Bolts or lag screws: This system uses a large threaded screw to fasten the individual logs together.
