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.
Log construction was the most common building technique in large regions of Sweden, Finland, Norway, the Baltic states and Russia, where straight and tall coniferous trees, such as pine and spruce, are readily available. It was also widely used for vernacular buildings in Eastern Central Europe, the Alps, the Balkans and parts of Asia, where similar climatic conditions prevail. In warmer and more westerly regions of Europe, where deciduous trees predominate, timber framing was favoured instead.
The two initial primary styles of log houses included:
Handcrafted log houses have been built for centuries in Fennoscandia, Fenno-Ugric areas such as Karelia, Lapland, Eastern parts of Finland. Also in Scandinavia, [1] Russia [2] and Eastern Europe, and were typically built using only an axe, knife and log scriber. [3]
Settlers from northern Europe brought the craft of log cabin construction to North America in the early 17th century, where it was quickly adopted by other colonists and Native Americans. [4] C. A. Nothnagle Log House, built in New Jersey circa 1640, is likely the oldest log cabin in the United States.
Pre-fabricated log houses for export were manufactured in Norway from the 1880s until around 1920 by three large companies: Jacob Digre in Trondheim, M. Thams & Co. in Orkanger, and Strømmen Trævarefabrik at Strømmen. They were factory built from sawn or milled logs, numbered and dismantled for transportation, and reassembled on the buyer's site. Buyers could order standard models from catalogs, custom-made houses designed by architects employed by the companies, or houses of their own design. Log houses from Thams were exhibited at the Exposition Universelle (1889) in Paris.
During the 1920s, the first American milled log houses appeared on the market, using logs which were pre-cut and shaped rather than hand-hewn. Many log houses today are of the milled variety, mainly because they require less labor-intensive field work than handcrafted houses. There are about 500 companies in North America which build the handcrafted, scribe-fit type of log house.
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. [5] 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%. [6]
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. [7]
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%; [8] 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.
Milled log homes employ a variety of profiles, which are usually specified by the customer:
Nearly every profiled log on the market features an integral tongue and groove milled into the top and bottom of the log; this aids in stacking and reduces the need for chinking. Wood is not airtight, but caulking or chinking improves energy efficiency.
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. [10]
Wood is a structural tissue found in the stems and roots of trees and other woody plants. It is an organic material – a natural composite of cellulose fibers that are strong in tension and embedded in a matrix of lignin that resists compression. Wood is sometimes defined as only the secondary xylem in the stems of trees, or more broadly to include the same type of tissue elsewhere, such as in the roots of trees or shrubs. In a living tree it performs a support function, enabling woody plants to grow large or to stand up by themselves. It also conveys water and nutrients between the leaves, other growing tissues, and the roots. Wood may also refer to other plant materials with comparable properties, and to material engineered from wood, woodchips, or fiber.
Lumber is wood that has been processed into uniform and useful sizes, including beams and planks or boards. Lumber is mainly used for construction framing, as well as finishing. Lumber has many uses beyond home building. Lumber is referred to as timber in the United Kingdom, Europe, Australia, and New Zealand, while in other parts of the world the term timber refers specifically to unprocessed wood fiber, such as cut logs or standing trees that have yet to be cut.
Plywood is a composite material manufactured from thin layers, or "plies", of wood veneer that are glued together with adjacent layers, having both glued with each other at right angle. It is an engineered wood from the family of manufactured boards, which include plywood, medium-density fibreboard (MDF), oriented strand board (OSB), and particle board.
Joinery is a part of woodworking that involves joining pieces of wood, engineered lumber, or synthetic substitutes, to produce more complex items. Some woodworking joints employ mechanical fasteners, bindings, or adhesives, while others use only wood elements.
Engineered wood, also called mass timber, composite wood, human-made wood, or manufactured board, includes a range of derivative wood products which are manufactured by binding or fixing the strands, particles, fibres, or veneers or boards of wood, together with adhesives, or other methods of fixation to form composite material. The panels vary in size but can range upwards of 64 by 8 feet and in the case of cross-laminated timber (CLT) can be of any thickness from a few inches to 16 inches (410 mm) or more. These products are engineered to precise design specifications, which are tested to meet national or international standards and provide uniformity and predictability in their structural performance. Engineered wood products are used in a variety of applications, from home construction to commercial buildings to industrial products. The products can be used for joists and beams that replace steel in many building projects. The term mass timber describes a group of building materials that can replace concrete assemblies.
A sawmill or lumber mill is a facility where logs are cut into lumber. Modern sawmills use a motorized saw to cut logs lengthwise to make long pieces, and crosswise to length depending on standard or custom sizes. The "portable" sawmill is simple to operate. The log lies flat on a steel bed, and the motorized saw cuts the log horizontally along the length of the bed, by the operator manually pushing the saw. The most basic kind of sawmill consists of a chainsaw and a customized jig, with similar horizontal operation.
A dovetail joint or simply dovetail is a joinery technique most commonly used in woodworking joinery (carpentry), including furniture, cabinets, log buildings, and traditional timber framing. Noted for its resistance to being pulled apart, also known as tensile strength, the dovetail joint is commonly used to join the sides of a drawer to the front. A series of pins cut to extend from the end of one board interlock with a series of 'tails' cut into the end of another board. The pins and tails have a trapezoidal shape. Once glued, a wooden dovetail joint requires no mechanical fasteners.
A log cabin is a small log house, especially a minimally finished or less architecturally sophisticated structure. Log cabins have an ancient history in Europe, and in America are often associated with first-generation home building by settlers.
Timber framing and "post-and-beam" construction are traditional methods of building with heavy timbers, creating structures using squared-off and carefully fitted and joined timbers with joints secured by large wooden pegs. If the structural frame of load-bearing timber is left exposed on the exterior of the building it may be referred to as half-timbered, and in many cases the infill between timbers will be used for decorative effect. The country most known for this kind of architecture is Germany, where timber-framed houses are spread all over the country.
Glued laminated timber, commonly referred to as glulam, is a type of structural engineered wood product constituted by layers of dimensional lumber bonded together with durable, moisture-resistant structural adhesives so that all of the grain runs parallel to the longitudinal axis. In North America, the material providing the laminations is termed laminating stock or lamstock.
Laminated veneer lumber (LVL) is an engineered wood product that uses multiple layers of thin wood assembled with adhesives. It is typically used for headers, beams, rimboard, and edge-forming material. LVL offers several advantages over typical milled lumber: Made in a factory under controlled specifications, it is stronger, straighter, and more uniform. Due to its composite nature, it is much less likely than conventional lumber to warp, twist, bow, or shrink. LVL is a type of structural composite lumber, comparable to glued laminated timber (glulam) but with a higher allowable stress. A high performance more sustainable alternative to lumber, Laminated Veneer Lumber (LVL) beams, headers and columns are used in structural applications to carry heavy loads with minimum weight.
Wood shingles are thin, tapered pieces of wood primarily used to cover roofs and walls of buildings to protect them from the weather. Historically shingles, also known as shakes, were split from straight grained, knot free bolts of wood. Today shingles are mostly made by being cut which distinguishes them from shakes, which are made by being split out of a bolt.
In woodworking, veneer refers to thin slices of wood and sometimes bark that typically are glued onto core panels to produce flat panels such as doors, tops and panels for cabinets, parquet floors and parts of furniture. They are also used in marquetry. Plywood consists of three or more layers of veneer. Normally, each is glued with its grain at right angles to adjacent layers for strength. Veneer beading is a thin layer of decorative edging placed around objects, such as jewelry boxes. Veneer is also used to replace decorative papers in wood veneer high pressure laminate.
A butt joint is a wood joint in which the end of a piece of material is simply placed against another piece. The butt joint is the simplest joint. An unreinforced butt joint is also the weakest joint, as it provides a limited surface area for gluing and lacks any mechanical interlocking to resist external forces.
Wood drying reduces the moisture content of wood before its use. When the drying is done in a kiln, the product is known as kiln-dried timber or lumber, whereas air drying is the more traditional method.
This glossary of woodworking lists a number of specialized terms and concepts used in woodworking, carpentry, and related disciplines.
Wood flooring is any product manufactured from timber that is designed for use as flooring, either structural or aesthetic. Wood is a common choice as a flooring material and can come in various styles, colors, cuts, and species. Bamboo flooring is often considered a form of wood flooring, although it is made from bamboo rather than timber.
Cross-laminated timber (CLT) is a subcategory of engineered wood panel product made from gluing together at least three layers of solid-sawn lumber. Each layer of boards is usually oriented perpendicular to adjacent layers and glued on the wide faces of each board, usually in a symmetric way so that the outer layers have the same orientation. An odd number of layers is most common, but there are configurations with even numbers as well. Regular timber is an anisotropic material, meaning that the physical properties change depending on the direction at which the force is applied. By gluing layers of wood at right angles, the panel is able to achieve better structural rigidity in both directions. It is similar to plywood but with distinctively thicker laminations.
Brettstapel, also known as dowellam, is a massive timber construction system, fabricated exclusively from softwood timber posts connected with hardwood timber dowels. It is a relatively simple method of construction that exploits low grade timber, not normally suitable for use in construction, to form load bearing solid timber wall, floor and roof panels.
Green woodworking is a form of woodworking that uses unseasoned or "green" timber. The term "unseasoned" refers to wood that has been freshly felled or preserved by storing it in a water-filled trough or pond to maintain its naturally high moisture content. This wood is much softer than seasoned timber and is therefore much easier to shape with hand tools. As moisture leaves the unseasoned wood, shrinkage occurs. This can be used as an advantage, as this shrinkage can help ensure tight joints. To enhance the effect of the shrinkage, a half of a joint may be forcibly over-dried in a simple kiln while its encapsulating component is left green. The components tighten against each other as the parts exchange moisture and approach equilibrium with the surrounding environment. The swelling of the dry tenon inside the shrinking “green” mortise makes for an incredibly tight and permanent joint despite a lack of adhesives. Bodging is a traditional green woodworking occupation, where chair components were made in the woods and exported to workshops where the complete chairs were assembled by furniture makers. Green woodworking has seen a recent revival due to increased media coverage and the renaissance of hand tool woodworking in general.
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