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How to triple the surface of a 1950s cottage with 21st century materials... all in less than two months! Follow this construction site of a modern composite wood extension with the explanations of System D.

Create a composite wood extension

Post-beam structural structure

Inspired by half-timbering, the constructive principle presented here (Boisalis patent) is that of a post-beam type supporting structure to which are added planks (walls and roofing) and seasoned caissons.
Prefabricated glulam, the frame is assembled on site.
Established every 4 m, the farms are connected over the entire length of the future building by failures.

Difficulty, cost, time, equipment

Difficulty: 4/4
Cost: € 1,200 / m2 (shell, excluding foundations and finishes)
Time : 5 to 6 weeks
Equipment: frame (plane, circular saw, chainsaw...), masonry (grinder, mass, levels...), carpentry (perforator, jigsaw saws, handsaw, radial...), zinc plating (bending machine, shears...).

Sandwich slabs and seasoned crates

The planks used to build the walls here are similar to sandwich panels: they consist of an expanded polystyrene core (96 mm thick) with spruce facing (thickness 20 mm). With a useful width of 205 mm, these planks are supplied in long lengths (here 13 m). Highly insulating (U: 0,28 W / m2.K), they are light (20.2 kg / m2) and easy to stack thanks to a triple interlocking tongue and groove.
For a better mechanical cohesion of the walls, these planks are implemented between two glued-laminated slats of 140 mm thick, one laid on the ground and the other at the top of the walls in the manner of a chaining. Treated in the IFH plant (insecticide, fungicide and water repellent), the wood is stained after the completion of the construction so as not to gray out.
On the roof, the seasoned boxes also have an expanded polystyrene filling that guarantees good insulation (U: 0.39 W / m2.K). Weighing just 16 kg / m2they are placed in the direction of the slope (sometimes in the length of the rampant) and butted.
Their pose is even faster than they are beveled at the ends. It is then sufficient to fix the under-roof screen, the counter-battens, the battens and to complete by the tiles to have a ventilated roof.

Turnkey project or option of self-construction

Executed by the project designer (Boisalis), the shell has mobilized four carpenters for about a month.

This operation involves putting "out of water-out of air" construction. From there, the delay before moving depends on the completion of the other lots... To those tempted by the adventure, the designer offers self-help...
The customer benefits from a training of one to two days to be able to realize himself the assembly. The intervention of the company's technicians is limited to the installation of exterior joinery and telephone assistance. This formula reduces by one third the cost: from 1 500 € / m2 turnkey, it goes to 1000 € / m2 (architect's fees, earthworks and networks, foundations and second work included)...

An extension in "L"

An extension in

The "L" extension with a floor area of ​​120 m2, deploys on a single level from the original construction, above a crawl space with the same footprint.

1. Establishment of farms

1. Establishment of farms

Farms are assembled near their defending locations. The anchor plates are fastened with 2 metal plugs.

Two shed-shaped farms

Two shed-shaped farms

Here in the form of shed (redent), each farm has two uprights joined by one entered (horizontal) and a crossbow (oblique).
Two or three struts stiffen the whole.

Assemble and peg

Assemble and peg

The mortise and tenon assembly is put in place with the aid of a tie strap before pegging the pieces.

Screw rafters, ties and struts

Screw rafters, ties and struts

After checking the squareness, the rafters, ties and struts are put in place and fixed with screws Ø 6 x 120 mm.
A powerful screwdriver is essential.

Finish cutting the crossbowman

Finish cutting the crossbowman

Cut into a butt joint on the side entered, the crossbow is tugged on it with the help of a nutrunner (or a ratchet).
The lag bolts engage in pilot holes, made in the rafters.

Raising the first farm

Raising the first farm

The first farm is closed.
It is braced by two rafters as its deck is not fixed permanently.

Laying of the second farm

Laying of the second farm

Still using the crane, a second farm is laid.
It is joined to the first farm by pre-machined breakdowns.
Until they are screwed, the parts are held by straps.

If necessary, fix the fixing plates

If necessary, fix the fixing plates

To compensate for the irregularities of the raw slab, it may be necessary to interpose shims under some of the fixing plates...

Attention to the verticality of the amounts

Attention to the verticality of the amounts

The establishment of farms continues to the opposite angle, not without checking, for each of them, the verticality of the amounts.

Stabilize with breakdowns

Stabilize with breakdowns

Installed as it goes, the breakdowns stabilize the farms.
If there is no crane, the last farm is raised by hand.

2. Preparation and fixation of the low rails

2. Preparation and fixation of the low rails

Before being put in place, the low glue laminates are drilled (Ø 40 mm) at the locations of the future wall outlets.
Be careful: the slats have one side facing outwards!
At this point, the low rails should be cut at the locations of the future sliding bays. Depending on the case, these cuts are performed with a carpenter's circular saw or a small chainsaw.

Seal the low rails

Seal the low rails

The low rails are protected from moisture by a bituminous sealing strip.
They are then wedged and screwed into the amounts.

Same spacing and spacers

Same spacing and spacers

The spacing of the trusses and the length of the rails are identical so that their joints are invisible.
Before being fixed, they are lined with polyurethane mastic.

Scribe the ends of the junctions as needed

Scribe the ends of the junctions as needed

If the junctions do not coincide with one of the trusses, their ends are indented.
This gives a kind of assembly mid-wood.

3 Wall mounting

3 Wall mounting

Depressed at an angle through the tongues of the planks into the uprights, the screws do not interfere with the assembly.
Their junctions are reinforced with expansive foam.

Spot openings

Spot openings

The locations of the openings are marked according to the plan, as and when the planks are laid.
Reservations will then be cut.

Define the angle of the rafters on the high rails

Define the angle of the rafters on the high rails

Raised at the false square, the angle formed by the rafters must be found on the upper face of the high rails.

Forcibly nest the finishing board

Forcibly nest the finishing board

Despite its 13 m long, the finishing board is lifted with ropes...
As for the sandwich planks, it is nested in force with a mass having to insert a martyr, made in a fall of smooth low.

Glue the smooth into the lower plank

Glue the smooth into the lower plank

The free end of the beam is blocked by a clamp: as it is impossible to screw in the lower plank (or in the nearest farm), it is "glued" with a little polyurethane mastic.

4. Installation of seasoned boxes

4. Installation of seasoned boxes

Before laying the boxes, an expansive foam bead is applied to the top rail. It will strengthen the seal (wind and snow) at the same time as it will remove the thermal bridges.

Nail the seasoned boxes

Nail the seasoned boxes

Aligned from the southern gable, the seasoned boxes are nailed using "L" points, driven into the rails and purlins.
The junctions of the panels are then filled with expansive foam.

Staple an underlay screen

Staple an underlay screen

A reflective sub-roofing screen, unrolled across from the bottom of the roof, is stretched and stapled on the sides of the caissons.
The strips are connected with tape.

Nail the contreliteaux, lay the battens

Nail the contreliteaux, lay the battens

After having nailed the contreliteaux on the caissons, the location of the battens is traced according to the size of the tiles.
Laying the battens starts from the bottom of the rampant, making sure to offset the junctions.

5. Zinc cladding and tile laying

5. Zinc cladding and tile laying

The ends of the boxes are closed with screwed wood panels which will be subsequently dressed with zinc.

Form the zinc sheets to the folder

Form the zinc sheets to the folder

The zinc sheets are shaped by folding, the ends bent outward to match the finishing staples.

Nail and staple zinc cladding

Nail and staple zinc cladding

Presented in their place, the zinc cladding is nailed to the top of the plywood panels.
Their ends are then joined by the zinc staples, threaded and then nailed from underneath.

Lay the tiles

Lay the tiles

The roofing work ends with the laying of the tiles, starting with a pinion.
For convenience, the tiles were mounted with a forklift and spread on the roof.

Re-cut the tiles directly to the grinder

Re-cut the tiles directly to the grinder

Again to go faster, the tiles are laid up on the hips and then resized directly to the grinder.
The junction of the two sides is covered with a closoir and then bricked roof tiles (similar to ridge tiles).

6. Berry grinding and bibs

6. Berry grinding and bibs

The reservations of the bays are put on the side of the future sleepers. The planks are re-cut and their end is dug a few centimeters to allow the embedding of a typed.

Refine the adjustments of the sides of the bays

Refine the adjustments of the sides of the bays

Retaillé in its thickness, the plank surmontant the bay will be able to embed the trunk of the shutter and to present the frame of the block-bay...
We can then postpone its dimensions on the inside of the walls and refine the adjustment of the sides of the bay.

Protect berry supports with bibs

Protect berry supports with bibs

Made of Oregon pine, the berry supports can not be left without protection...
Zinc bibs are made to dress them up.

Cut and braze bibs

Cut and braze bibs

The bibs are cut out of zinc sheets. Their longitudinal edges are folded on one side upwards and on the other, downwards. These pieces are brazed with tin after etching.

7. Installing the sliding bays

7. Installing the sliding bays

A bead of polyurethane putty is first deposited on the low rail at the location of the flap, clamped by a clamp and nailed at its ends.

Add typed

Add typed

Before presenting the frame, all that remains is to add the keys, whose ends are rectified with the saw to facilitate their embedding. They are then glued on their reverse, presented and screwed through the faces of the planks.

Paste and screw the frame

Paste and screw the frame

The frame is also placed on a bead of polyurethane putty before being screwed into the keys.

Ensure airtightness

Ensure airtightness

Before adding the opening, a sealant silicone sealant is placed in the upper part to ensure airtightness, behind the trunk of the roller shutter.

Use the thickness of the plank

Use the thickness of the plank

The small windows of the west facade, like the sliding windows, are glued and screwed into the taps added in the thickness of the planks.

Install the portholes

Install the portholes

Screwed from the inside, large fixed portholes take place in a circular cut. A strip of plywood (glued to the foam expansive) serves as a typed.

Dress up the portholes

Dress up the portholes

The plywood strip is ground with the plane before sealing with silicone sealant.
A round cladding exotic wood will then be screwed on the facade.

Installing shutters on rails

Installing shutters on rails

A custom shutter is suspended from a sliding door rail screwed under a half-chevron.
This flap is grooved at the bottom to be guided by an angle.

Identical moldings for edges and bays

Identical moldings for edges and bays

The edges of the outer walls are dressed by Oregon pine moldings, the same type as those provided around the tables of the berries.

Supplies

• Prefabricated Farms
• Sandwiches
• Seasoned caissons
• Underlayment screen
• Batteaux, contreliteaux and tiles
• Bitumen felt, polyurethane sealant and polyurethane expansive foam sealing strip
• Screws and tips according to needs

Electrify: a few days are enough

Electrify: a few days are enough

Installed at the same time as the joinery, the electricity required few days of work...

On the one hand because the extension is deployed on one floor and, on the other hand, because most of the cables meander to the ground.
Retained by necklaces pegged in the slab, they are covered by a parquet floor on joists.
The cables go up into the holes drilled initially in the low rails, the locations of the sockets, switches and appliques being cut with a hole saw.
No bleeding is necessary: ​​a heated ball (photo opposite), digs the walls by the interior by sinking by gravity in the thickness of the insulation.


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