Draft:Wooden house

Small wooden building.

Wooden houses are houses constructed primarily from wood.

There have long been many types of wooden houses, the main building models of which are:

• house with pole/beam structure;
• The house made of solid plywood panels;
• the wooden frame house;
• the stacked solid wood house (planks, trunks or logs, wooden block).

Benefits

Wood construction in Oregon.

Wood, like stone and brick, is a durable construction material, thus allowing wooden houses to stand for decades or even long; there are several hundred-year-old half-timbered houses in different parts of Europe (Germany, France, Norway, Switzerland, etc.) and in Asia.

Wood and carbon dioxide emissions

House built in 1644, street Volta, Paris.

During the manufacture of materials used in the development of any home, energy is consumed but especially pollution is released into the atmosphere in the form of mainly CO2. Depending on the materials processed, the amount of CO2 produced differs. Wood can reduce the amount of CO2 released into the atmosphere by half. In addition, wood has a significant CO2 storage capacity, which limits its release. However, the destruction of wood (natural or by combustion) results in the release into the atmosphere of all the CO2 previously stored.

Another environmental aspect of a wood construction site is the small amount of waste on the site because all the waste can be recycled or burned in a heater.

House with pole/beam structure

Wuzhen village, China.

The supporting structure of the house consists of columns and beams usually made of solid wood or glulam, rigidly assembled between them which gives it a great formability. Between these load-bearing elements are inserted bay windows that, when fixed, can be installed without the use of intermediate joinery, non-load-bearing insulating masonry blocks (for example, hemp concrete blocks), wall elements that may consist of a wood frame (as in the wood frame house described below) or a stack of planks as in the case of the frame «at the meagevanne» (Megève region).These walls serve as fillers and have no bearing role. The construction can be done on site, but gains a lot of precision and reliability to be carried out in a workshop. This type of construction allows large spans preserving large free volumes and very open facades. Its complexity of realization usually reserves it for quality achievements or southern facades of bioclimatic constructions.

House in solid wood panels

This mode of construction tends to develop in France. It is common in Austria, Germany, Belgium and Switzerland. The main manufacturers are: Schilliger, KLH, Finnforest, Binderholz, MHM, Biospeedhome, etc.

This wood construction technique is a combination of frame systems and solid timber: aesthetically, it has the same appearance interests as the wood frame house (cladding, coating, painted or rough on the outside on a reported insulation and with multiple possible finishes for the interior, including the natural wood appearance of the panels), with the performance of solid wood in terms of inertia. The solid panel material makes it possible to optimize the use of wood by giving it equivalent mechanical characteristics in all directions, eliminating the veil and deformations due to aging or hygrometry, and allowing unprecedented architectural freedom.

This system is expected to develop with the increase in the energy and thermal performance of buildings.   It is also recognized that massive panel constructions are more earthquake resistant [ref. needed]. There are currently buildings of more than six floors composed of panels, some even reaching ten floors.

The current techniques allow the realization in the factories of walls of great length (up to 24 m) and variable thickness (from 7.8 to 50 cm) obtained by the assembly of wooden boards glued or nailed to each other in multiple crossed folds. This type of wood construction ensures remarkable stability over time.

These panels against glued can make a house from floor to ceiling. The house can be built on a conventional concrete slab, or on stilts, in which case the floor can also be laid in panel. All walls made with this type of panel are load-bearing. Floors and roofs can also be made as well.

These panels are resistant to strong overhangs, which allows balconies without support by beams.

Wooden frame house

The wood frame house is the best construction technique for most regional styles, so it's the most common. The walls of the wooden frame house are made on the basis of a structure consisting of wooden frames spaced 40 or 60 cm apart (in general) between which are placed the insulating materials. This construction technique also allows the prefabrication of complete walls in the factory, sheltered from the weather. The completion of the canopy enclosure can be achieved in just a few days, since there is no drying time.

The tendency to better insulate houses leads more and more to double this framework with external peripheral insulation of heavy insulating material (type wood fiber for example) that improves insulation, provides better thermal dephasing for the benefit of summer comfort and eliminates all thermal bridges attributable to the wood frame. The wooden frame house allows more economical and quick to implement expansions.

Exterior cladding serves as a bulwark against bad weather. It is often made of cladding, that is, wooden boards that can be painted, treated or left natural. Wood (especially untreated) exposed to sunlight and the elements will take on a gray hue over time, but will not lose any of its mechanical qualities. The exterior siding can also be made with a coating.

Wooden holiday homes in the Jura.

The inner walls are most often made with plaster panels offering multiple possibilities of finishes (paint, wallpaper, etc.).

Prefabrication

One of the advantages of wood frame construction is that it allows the workshop manufacture of wall panels, dry, safe. Once the walls are finished, they are loaded on a semi-trailer and then mounted on the site using a crane arm or crane.

Thus, in two days, the walls are standing; it remains only the floors or framework to mount before the house is out of water. This manufacturing method requires anticipation, good supply management, design mastered to the millimeter, synchronization with other trades, but it ensures that the wood has not been subjected for several weeks to bad weather (unlike mounting walls on the slab).

A more successful stage of prefabrication is to manufacture in advance, in the workshop, the floors and the frames. For example, a framework is in the form of boxes that are mounted on site by a crane.

Insulation

It is often argued in favor of the wooden house that for a quality of insulation identical to that of a masonry construction, the wall of a wooden construction is 40% thinner, This represents additional significant square meters in case of urban planning constraints and resale. In practice, the interest of wood construction lies, among other things, in the possibility of making a house much better insulated and more comfortable than a masonry house. Therefore, it is logical to increase the insulation thickness significantly, as explained above, the additional cost being very limited as a percentage of the total construction price, and in any case minimal compared to the expected energy savings. In addition, since a wooden house is not designed on the model of a masonry house, there is a good chance that the architecture and surfaces will differ. The surface gain is therefore no longer significant.

However, the thermal resistance of the materials used for the construction of wooden frame houses is different from the materials used for the construction of traditional houses. The thickness of the different materials for the same thermal resistance (0.50 m2 °C W 1) is as follows:

• solid concrete: 88 cm;
• Hollow block: 52 cm;
• Pisé: 39 cm;
• Solid brick: 28 cm;
• Softwood: 7.5 cm;
• hemp concrete: 6.5 cm;
• cork, cellulose panels, mineral wool: 2 cm.

The surface gain will depend on the type of construction as well as the type of material used.

Stacked solid wood house and wooden masonry

Traditional construction, Eastern Europe.

Often called a cottage, it consists of solid wood walls mounted in stacks of planks (rectangular finish), logs (smooth finish) or charcoal (rustic finish).

Wood masonry is the use of solid wood blocks. These are stacked using the masonry technique. This technique gives the opportunity to realize all architectures, promotes self-construction and the realization of solid wood house with a minimum of tools.

New techniques now make it possible to mount a wooden chalet by assembling pre-cut wooden planks in kit. The thickness of the planks is generally between 28 and 60 mm depending on the manufacturer and the range. The assembly takes place in stages following a manual and requires very little knowledge in carpentry or framing.

Lack of inertia

Despite its thickness, solid wood has a so-called light inertia. This is why this wooden construction technique is very common in North American countries or in the mountainous regions of Europe.

On the other hand, wood is an average insulator (lambda coefficient of 0.12) compared to materials specifically intended for this use (0.04 on average for rock wool, wood fibre, cellulose or hemp). To obtain an insulation coefficient comparable to that of a wood frame wall, it is essential to add a thickness of insulation, ideally from the outside, so as to benefit from the inertia of solid wood inside the construction. The exterior insulation can then be lined with thick boards that will restore the «chalet» spirit. It is no longer necessary to provide insulation inside. This allows the occupants to fully enjoy the warm presence of wood, for a long time.

The modern design of the stacked solid timber construction allows very significant thermal gains by the design of the walls of the buildings: simple timber with insulation from the outside (avoids thermal bridges that cause significant thermal leakage) or double planks that trap the insulation (the thickness of which can vary depending on the location and needs).

The species most frequently used for this type of construction are larch, spruce, red cedar, scots pine and douglas fir.

New wooden houses usually offer very reliable insulation thanks to a double plank system with insulation in between. For example, instead of having a wood thickness of 120 mm, there are two 60 mm planks with a layer of 80 mm insulation inside.

Preparation

Woodworking must meet certain criteria to have a home offering the best possible quality. It is important to take into consideration when the tree needs to be felled, and the method of drying, to obtain strong and well-preserved wood.

The tree must be cut in winter, or possibly in autumn, when the tree is at rest and the sap circulates very slowly [ref.necessary]. It is then said to be "not sap", and therefore less prone to fermentation and insect attacks.

Natural drying, which can take at least a year, offers even better resistance to timber [ref. needed]. It must be protected from the elements, but stored in the open air, to have a good air circulation and thus avoid the accumulation of moisture and proliferation of fungi and other parasites, then be stored for a week in the dry, in a depot, before being worked.

Industrial wood does not always respect the right cutting season. It is also cut in spring and summer, and undergoes kiln drying, which gives construction wood, certainly cheaper to acquire, but also, of lower quality and will have to be treated more often.

See also

• Further information on wood (building material)
• Straw house
• Timber industry

References

General

• Building with wood. Meeting with 30 architects, Build with the architect, 2000, 84 p.

Specific

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Categories:

• Wooden architecture