- Practical advice
- Wood frame: freedom of forms
- Live warm in a wooden house
- Wood and nails for the frame
- Floor foundations
- The assembly of the walls
- Wall mounting
- The floor of the house
- The finishes of a wood construction
- Laying the wooden sole
- Installation of wall panels
- Laying interior partitions
- Insulation of wooden walls
- Installation of the frame
- Facade cladding
Taking advantage of significant technological advances, wood is gaining strength in the building. Twelve times more insulating than concrete, it is at the origin of architectures both varied, adapted to climates, integrated landscapes, sustainable and evolving.
Burning question for all candidates to the natural habitat! Although it is true that it fuels the fire, solid wood burns slowly, without deformation, and resists bending longer than stone or concrete that split and burst. Similarly, metal structures expand under the effect of heat and lose all mechanical strength. Well protected from flames by the panels that dress (plasterboard, insulating mineral wool...), insurers do not apply surcharge to the wood frame house... which meets the same criteria of behavior and than other single-family houses.
Bringing together businesses and building professionals, the Association of French Timber Construction Companies is working to better understand this type of habitat for the general public.
She is at your disposal to answer your questions and direct you to the builders in your area.
Information: [email protected]
The renewed interest in wood construction reflects a legitimate desire to live in a healthier, warmer home.
Thanks to progress in sawing and gluing, the reach of wood is no longer limited to the size of its trunk alone. Thus, instead of conventional posts and beams assembled by tenons and mortises, a light frame made of resinous erected, then nailed and fixed with metal connectors ensures a better rigidity. Insulating and decorative bracing panels then hide this "skeleton".
Wood frame: freedom of forms
The wood allows to build a habitat whose thin walls provide a huge saving of space without compromising comfort. The range of shapes and volumes gives me the freedom to create mezzanines, open large windows bringing light and fluidity to every room in the house. To this freedom of concepts are added its lightness, its evolutionary character and its speed of implementation.
For example, for the same load, a beam of 3 m span weighs 60 kg of softwood, 80 kg of steel and 300 kg of reinforced concrete. Light, the wooden house adapts to different layouts and nature of land. Easily removable, the "walls" can be moved to create new parts. The wood does not require binder, the sites are fast and without nuisance. Depending on the importance of the dwelling, it takes a week to build it, plus about three months for the foundations and finishes.
Live warm in a wooden house
When the wood is used in solid logs, its natural properties ensure, in both summer and winter, excellent thermal and hygrometric regulation. A 12 cm thick wall is equivalent to a solid brick wall of 50 cm, or 140 cm of solid concrete.
As a framework, the wood remains an excellent insulator, as evidenced by its coefficient of thermal conductivity: from 0.12 to 0.28 (depending on the species), against 1.15 for glass and 0.70 for plaster. Remember that the lower the number, the better the insulation. For example, at equal volumes, a wood-frame house consumes up to three times less energy for its heating than an uninsulated masonry house.
Wood and nails for the frame
The system consists of a skeleton of wood (northern pine) that is dressed with plywood, rock wool (or glass), a rain screen and plasterboard. When the house has one or more floors, it is called platform skeleton. At each level, a joist is laid on the top of the walls that is covered with a floor on which will be placed the walls of the next floor.
The assemblies are made with stainless steel connectors and corrugated nails. Wall cladding is done with mineral wool panels, gypsum boards, rain rollers, siding boards and paneling. In frontage, a cladding forms a decorative facing and reinforces the thermal insulation.
The project followed (designed by Maisons Alaska and led by Emmanuel Menet) concerns the construction, near Orléans, of a house of 170 m2 with habitable attic space. The cost of a frame house "open walls" is between 686 and 914 € per m2. Note the existence of walls ready for use, so-called "closed" because incorporating insulation, plywood, gypsum board... Prémontés, these panels require transport and lifting means consequent.
The construction is carried out on a foundation in walls of blocks and slab of concrete which maintains a crawlspace.
Depending on the region of implantation, it will be necessary to provide antitermite treatment by laying a polyethylene film creating an impassable barrier. A wooden floor is fixed on a low rail sealed on the walls with anchor bolts. This sole is made of edge joists that are laid on a bitumen felt to isolate it from moisture.
The floor joists rest on it and are evenly spaced. Their spacing is stiffened by spacers or braces cross nailed. The joists do not cover the entire width of the house, are based on intermediate sheds walls. Before nailing the floor panels, semi-rigid insulation boards are inserted between the joists.
The assembly of the walls
Key part of the frame, the walls are formed of a low sand pit and a high sand pit connected by uprights. These elements define spaces called "open" to fill and hide with various elements (insulation, drywall...).
They are mounted on the floor with galvanized or stainless steel tips. Windows and doors take place in rectangular frames. The loads of the upper floor are taken up by lintels formed of two joists nailed on a sole. In the case of descents of high loads (stairs for example) the jambs carrying the lintel are doubled and the latter is connected to the upper sandbox by spacers.
Triply or chipboard panels are nailed to the outside. These "bracing sails", close and stiffen the structure. They are protected from moisture by a rain screen: microporous plastic film that lets air through but not water.
Once assembled, the walls are erected by hand or with the help of cylinders to form bearings. After checking their alignment and plumb, the end posts and bracing plates are nailed against each other. The walls are fixed to the ground with screwed connectors.
In the interior, the walls are insulated with rockwool and then a vapor barrier creating an air gap that prevents the passage of condensation. Plasterboard and paneling are, in finishing, a fire barrier and a decorative coating. Behind this siding, it is advisable to leave an air gap to pass the electrical ducts and pipes. Thus, with this circulation of air, the wood of the frame remains dry and offers excellent insulation.
The floor of the house
The walls of the ground floor are belted with a new sole on which is laid a high rail. A new floor is mounted. The insulation filling the voids between the joists is on the other hand no longer held by planks, but by a joist in slats of wood.
The staircase requires a hopper opened by a rectangular frame whose double joists delimiting it. Two lugs supported by metal hooves take outside the resized joists of the floor. The two gables are identical to the walls of the ground floor.
As a frame, small farms assembled with connectors and secured by spacers receive insulating panels, a plywood deck, a roofing felt and battens that will support the tiles.
The finishes of a wood construction
The braces are protected by a cladding made of solid wood strips. They are nailed on cleats to create an air gap with the supporting structure. Assailed by the sun, rain, humidity and cold, the wood sees its original color turn blue gray. If these changes in appearance alter little mechanical qualities, they sometimes weaken. It must therefore be protected on the façade by appropriate treatment.
Mats, satin or shiny polyurethane varnishes enhance the nuances of wood but are quite vulnerable to ultraviolet. Depending on the exhibition site, their performance ranges from three to five years. Rich in dozens of colors, the wood paintings provide a personalized decor while allowing "breathing" support on the conditions of not applying more than two layers. After four to eight years, they flake off and let the wood see. Colorless or tinted, the stains form a supple microporous film that prevents wood grittiness and water penetration. Applied in two or three layers, they have the advantage of being degraded slowly by chalking. To renew their application (every three to six years), a light sanding is enough.
Laying the wooden sole
A low rail is placed on the foundation walls after inserting a bitumen felt to isolate it from moisture. On this "sole", take place the pre-mounted walls with a height of 260 cm.
Installation of wall panels
The walls are composed of low and high runners connected by uprights and closed by a bracing which makes them indeformable. Their assembly is done on the ground with the help of spikes.
Horizontal or vertical rectangular frames define the openings of the walls. Their uprights are reinforced by three joists nailed against each other and a lintel made of solid wood.
The alignment and plumb of each panel is controlled relative to the sole and the adjacent wall. This done, their amounts and contraband are nailed against intercalated posts.
With a width of 40 to 240 cm, the walls are supported with herringbone scarves. They will withstand any gusts of wind during the five days of construction.
In the upper part, they are belted with a sole distribution on which will take place the farmhouses of the frame. Their interstices will support the floor of the livable roof.
After folding the felt, a square is placed at the foot of each metal upright. Lag screws are screwed into their homes to secure the walls to the slab.
Laying interior partitions
In the house, a glulam beam delimits the kitchen and the living room. It is provisionally hoisted several on the smooth, before resting on two solid oak poles.
All the exterior walls in place, the partitions delimiting the rooms are erected on soles fixed on the concrete slab. They are supported while waiting for the roofing.
Insulation of wooden walls
From the inside, the walls are insulated with glass wool or sheep's wool, linen... then covered with a vapor barrier, a plasterboard and a decorative coating.
Installation of the frame
A crane truck raises the trusses of the frame and deposits them on the top of the walls. A stair hopper is made from a rectangular frame delimited by doubled joists.
The farms forming the gables are erected first. Provisionally supported, they are fixed on the upper sole of the walls with nails that are uncracked and crossed.
One by one, the trusses are positioned with an interval of 60 cm and secured together by spacers... both at the level of the floor at the level of crossbowmen.
Planks of small sections are fixed in the cross of St. Andrew between the legs placed at the feet of the farmhouses. Similarly, the links (located in the upper part), are joined continuously.
Connected to the main beams by connectors, the joists rest on the sole of the walls. Their spacing is maintained by braces in cleats nailed in cross.
In frontage, the walls are protected from the humidity by a rainscreen. A vertical framework of cleats is nailed to the latter to support the tongue and groove blades of the cladding.
At the edges of the roof, cleats define the shape of the pinion and complete the attachment of the rain screen. They will facilitate the subsequent cutting of the cladding boards.
The horizontality of the first blade is controlled flush with the foundations with a spirit level. They are fixed with 45 mm stainless tips using a compressed air nailer.
Cut to size, the following blades are mounted in rows, taking care to offset their ends. In finish, a wood paint protects the support while leaving it "breathe".