Дома из бревен: строительство, сушка и особенности

House built from wooden logs

A log house, or log building, is a structure built with horizontal logs interlocked at the corners by notching. Logs may be round, squared or hewn to other shapes, either handcrafted or milled. The term "log cabin" generally refers to a smaller, more rustic log house, such as a hunting cabin in the woods, that may or may not have electricity or plumbing.

The logs in log houses have a varying degree of moisture content; all logs have moisture when freshly cut. Handcrafted logs moisture will naturally leave the timber, drying it out until it stabilizes with its climate. This drying out causes movement and shrinking of the log's diameter. As logs and timbers dry, the differential shrinkage (radial versus tangential) causes small cracks (known as "checks") to open slowly over time. Checking is a natural process in both air and kiln dried logs. This occurs in all log houses regardless of construction method or how the timber is allowed to dry, and is considered normal. Milled logs are processed in a different manner from handcrafted logs. Logs destined to become milled logs may become one of several types, depending on the desired quality and results.

Logs that are cut from the butt forest, brought to a mill or to a log house construction yard, have their bark removed and are used to build a log house shell, handcrafted log houses, or sent through profiling machines usually referred to as "green" logs if they have not been air or kiln dried. "Green" does not refer to color, but to moisture content. The actual moisture content of "green" logs varies considerably with tree species, the season in which it was cut, and whether sapwood or heartwood is being measured. Green logs may have a moisture content ranging from about 20% to 90%. One type of air dried log is "dead standing," which refers to trees which have died from natural causes (bug kill, virus, fire etc.) and cut down after they died. Standing dead trees may be cut one month or several decades after they died, so the term "dead standing" does not necessarily mean the logs have dried down to equilibrium moisture content. Dead standing logs can be green, or more or less dry. After construction, green logs dry in service in the log building. Within about four years, green logs which are part of a completed log house reach equilibrium with local conditions and have an equilibrium moisture content of between 6% and 12%, which varies by local climate, season and location.

Some log home companies let the fresh cut logs (or milled timbers) sit outside in the open air to dry naturally. The timbers may be stacked with spacers (known as "stickers") between them. This process allows the moisture content of the logs to naturally fall as the timber dries. In areas of high humidity, it may require as much as one year per inch of log thickness to dry. Arid climates may require less. A log with a diameter of 8 inches will usually reach equilibrium in about 18 months in the Rocky Mountains of North America. Air circulation is critical or the logs may begin to rot before properly drying, especially in humid regions. If the logs are to be dried to equilibrium with the local climate the process may take several years, depending on the location and size of the timbers. In some environments, the logs must be kept under some type of roof or cover to reduce the impact of rain storms on the drying process. Once the logs have dried for the desired length of time, they are profiled prior to shipping. Profiling usually does not take place until shortly before shipment, to ensure that the logs stay as uniform as possible. It is uncertain whether this process is advantageous; it depends on many factors such as local climate, wood species, its size, and the location of the log structure.

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 them; however, 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 drying time from many months to several weeks. Kiln drying usually results in an average moisture content of 18 20% ("average" means the average moisture content of the outside and the center of the log). In North America, logs reach equilibrium moisture content at about 6% and 12%; since most kiln dried logs are dried down to about 18% to 20% moisture content, kiln dried logs can be expected to shrink and settle over time, but to a lesser extent than green logs.

"Laminated" or "engineered" logs are a different approach to log house building. Full trees or (alternatively) sawn cants (unfinished logs to be further processed) are brought to a mill with a dry kiln, the bark is removed and the trees are sawn into boards usually no more 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 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. Now there are also Non Settling log profiles available. 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 (RF) energy to cure the glue in minutes; the other uses a high pressure clamp, which holds the newly reassembled timbers under pressure for 24 hours. Once the glue has dried, the result is a "log cant" that is slightly larger than the buyer's 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 small timbers by using a combination of face and edge gluing and a process known as finger jointing. Boards which would be scrap at another mill may be used in the center of a laminated log or beam to minimize waste.

Scandinavian Full Scribe, also known as the "chinkless method", is naturally shaped, smoothly peeled (drawknifed) logs which are scribed and custom fitted to one another. They are notched where they overlap at the corners, and there are several ways to notch the logs. In the flat on flat method, logs are flattened on the top and bottom and then stacked (usually with butt and pass corners). Milled log houses are constructed with a tongue and groove system which helps align one log to another and creates a system to seal out the elements. With the tight pinned butt and pass method, the logs are not notched or milled in any way. They are in a single course and do not overlap; vertical pairs of logs are fastened with tight, load bearing steel pins.

Half Log: The structure is built with conventional building techniques, and "half log" siding is applied to the exterior and interior walls to replicate the look of full log construction. Some half log sidings may also have saddle notch, butt and pass, or dovetail corners to give a more realistic appearance. Palisade style: The logs are standing on end, and are either pinned or bolted together. Piece en piece or piece sur piece. Similar to post and plank above: Uses short logs (e. g. 8' long) lying horizontally between upright posts, resembling post and beam construction (but usually lacking the complex notching seen with post and beam). Piece en piece typically uses a large (8"x 8") vertical corner post. It is important that a vertical component (often 3"x 6") be placed on both sides of each window and door. A unique house type in the Oberlausitz region where Germany, Upper Lusatian house or Umgebinde in German. Part of the ground floor has log walls inside the posts of a timber frame.

Once fabricated and assembled, the shell of the log house may be disassembled and the parts shipped to the building site. This allows for centralized manufacturing of the house, and relatively quick construction on site. Full scribe fit handcrafted log construction is a method of precisely marking where to cut each individual wall log to provide a tight fit 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 fit of naturally shaped logs have aesthetic appeal. Log houses which settle require slip joints over all window and door openings, adjustable jacks under vertical elements (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.