The Content Of The Article:

From roof walls to floors, ready-to-install structures are legion! How to find between constructive systems, elements in kit, price, performances? Overview...

renovate his house with pref materials

For many years, the materials manufacturers have been competing with imagination and innovation to offer prefabricated elements that facilitate implementation while displaying quality and performance in accordance with current regulations. Whether traditional concrete, cellular or insulating (pumice, expanded slate...), clay or crushed limestone, these elements are manufactured in series.
They come in four "big families": products for masonry (standard or technical concrete blocks, cellular concrete...); structural works (joist floors, stairs...); reconstituted stone to decorate and decorate home and garden (siding, slabs, paving stones...); roof panels "three-in-one" (seasoned boxes, sandwich panels...).

Block or rectified block

Regular shape, resistant, manuportable and very affordable (1 to 2 € per unit), the breeze block, usually hollow, is the most common material in construction. On the other hand, it is the least insulating (R = 0.23 m².k / W). Blocks (l 50 x L 20 x 10, 15 or 20 cm) are arranged in cross-seamed rows.

But at the cost of significant mortar consumption (80 kg / m2 approximately with joints 1 to 1.5 cm thick). In addition, the walls must be insulated with insulation from the outside or the inside.
To remedy the disadvantage of this "traditional" installation (quantity of cement to waste), the industrialists have designed a block with thin joints (produced in a High Environmental Quality approach), simple to implement, with a mortar consumption which drops to 8 kg / m². But the first row must be mounted perfectly level and plumb (no catch-up possible).
It is a block whose faces are ground mechanically with a dimensional tolerance of the order of a millimeter. Its perfect flatness allows a horizontal laying on a binder-glue deposited with the roller applicator (more need of cement mixer), while the vertical joints fit dry thanks to a system of groove and tongue. Thus, horizontality and plumb of the wall are obtained automatically. The rapid installation of this constructive system offers 30 to 40% time savings.

Floors with girders or slabs: compulsory insulation

Traditional floor solutions with beams and joists are varied, but cumbersome to implement. That's why prefabricated floors have long been popular.

Very used in construction as in renovation, the floor with beams and concrete slabs is formed of lattice girders in reinforced concrete (reinforcements coupled to inverted metal V), or prestressed (so-called reinforcing bars), in I or inverted T.
Most often, the gap is filled with concrete blocks (called "slabs" or "bottom formwork"), before casting a compression slab. The low weight of the elements does not require large lifting means, nor high qualification, and the cost (50 € / m2 about) is interesting. The reverse of the medal: the limited range of beams (4.8 to 5 m), the need to use props and the creation of points of support (walls of splitting).
Not to mention the absence of sound and heat insulation. But to remedy this, "intervous" molded expanded polystyrene (EPS) are preferred. Lightweight, they fit easily between beams (range up to 6.2 m) and are complemented by "breakers" that provide a thermal break between floor and load-bearing walls. The "longitudinal" breakers are placed parallel to the front walls, while the "transverse" isolate the walls of the split.
An ideal formula to create a floor on crawl space, ventilated and isolated, less energy consuming in heating than slab poured on slab. To solve the problem of long spans, the rhythmic rectangular elements of recesses (longitudinal cells) of prestressed concrete by strained steel wires, offer up to 15 m of scope for a current width of 1.20 m. Thick (16 to 35 cm), they have a structural strength of 230 to 500 kg / m2 and a sound insulation, with a significant weight. This type of "floorsec" is particularly popular in the collective. It accommodates many homes large areas.
After lifting, the slabs are laid contiguously on the load-bearing walls (minimum support depth of 3 to 6 cm depending on the materials), and assembled by a concrete keying, forming the finished floor. The installation is carried out without shoring (lost formwork) and is satisfied with an equalization screed.

Reconstituted stone: more real than nature

Cladding, flagstones, paving stones, pool edges, fence pillars... floors on the walls, from the house to the garden, the recomposed stone does not leave any marble.
The reason? If the charm of the cut stone is undeniable, it is expensive (extraction, size, pose...).

The reconstituted stone, cheaper, is made in the form of paste (from crushed rock, lime, white cement, resins, pigments and water), then cast in elastomer molds made from impressions taken from old regional materials.
It can thus reproduce a large number of aspects and materials (limestone, shale, dry stone, brick, pebble and even wood). Only constraint, the application of a hydro-oil-repellent treatment to deal with the risk of stains.

Roofing and roofing: respected style, integrated insulation

Porous tiles, deformed lathing, defective flashing... as soon as signs of failure appear, a makeover is necessary.
Especially since a poorly insulated roof accounts for 30% of heat losses.

If the roof is to be completely renovated, after its removal (tiles, battens and rafters), the objective is no longer to separate the different elements but to use for example "sandwich panels" or "seasoned boxes" ( insulation process from the outside). At the same time support of cover, insulation and interior decorative veneer, these boxes enclose the thermal insulation (EPS, polyurethane foam, mineral wool...) sandwiched between a decorative underside (plasterboard, paneling, veneers... ) and a water-resistant exterior siding to which the roof supports will be attached. Some are even framed by two stiffeners which, like lateral chevrons, are ready to receive the battens.
The absence of thermal bridges thanks to the continuous insulation (9 to 19 cm thick), maximum habitable volume and subface ready to paint or decorate are the advantages of this "all-in-one" process. Specific to roofs topped with round tiles, corrugated sheets (cellulosic fibers) are fixed directly on the purlins of the frame and facilitate the wedging of the tiles channel.
We can prefer the insulating wave panels that ensure further insulation from outside. They are formed of a core (polyurethane foam), taken between a gypsum plasterboard (decorative support full side) and a corrugated sheet fiber cement (exterior facing).

The opinion of the expert *
"It is undeniable, the prefabricated construction elements offer a saving of time by their ease of implementation and thus open to a wider public.In spite of an additional cost of 16% for a new house meeting the RT 2012, the sales of insulation blocks have increased significantly. "
* Christian Lejet, director of the Point P division.

block with honeycomb structure in pumice concrete

This honeycomb block made of pumice concrete guarantees good thermal resistance thanks to the air bubbles it contains. Walls and corner blocks are armed with curved irons and stringers, then boxed to receive concrete.

rectified concrete block

Resistant, this rectified concrete block must be associated with a 12 cm insulator, thermal breakers and anti-thermal bridges (volcanic rock and polyurethane foam), to meet the RT 2012.


The result of the combination of Granulex walls and polystyrene graphite insulation, this latest-generation planelle avoids the use of thermal breakers.

hourdis in PSE

Marrying the joists, the EPS (expanded polystyrene) slabs help limit heat loss. Associated with peripheral switches, this type of system corrects thermal bridges.

Performance of different building materials

Block of volcanic rock

Block of volcanic rock

With its cells filled with EPS (expanded polystyrene), the "Comfort +" block of Alkern offers a high thermal resistance (R = 2.01 m².K / W) and it has a good grip of the coating (50 x 25 x thickness 20 cm, 12 kg the block).

Pumice concrete

Pumice concrete

The "Fabtherm" block from FabemiIl combines ease of installation (glue consumption: 1.6 to 2.6 kg / m2) and thermal performance (R = 1.04 m)2.K / W). Insulation reported with plasterboard (thickness 13.5 cm) is justified to obtain a R ≥ 5 m2.K / W (50 x 20 x 20 cm, weight 16 kg, 8 blocks / m2).

Block of pumice

Block of pumice

Thanks to its vertical cells, the Cogetherm pumice stone block offers thermal insulation / inertia capable of storing winter solar gain and containing summer heat. It is composed of 92% of pumice, iron oxide, clinker and lime (49 x 19 x thickness 20 to 25 cm, R = 1.3 to 1.35 m2.W / K, 16 to 17 kg the block ).

Concrete and slate block

Concrete and slate block

Based on expanded slate, the "Easytherm" block from Perin & Cie combines high mechanical resistance (L 60) and thermal performance (R = 1.27 m².K / W), it is satisfied with a single layer RT3 coating. Its corner block for chaining avoids cuts (50 x 20 x 20 to 25 cm, 12.5 to 16 kg the block).

block of cellular concrete

Block of cellular concrete

Masonry with staggered joints with an adhesive mortar, Xella's "Thermopierre" blocks interlock by groove and tongue. (62.5 x 25 x thickness 25, 30, 36.5 or 50 cm, R = 2.58 to 5.3 m².K / W, 350 to 550 kg / m²).

Distributed insulation brick

Brick with "distributed insulation"

Self-supporting and self-limiting, the "Climamur" brick from Porotherm-Wienerberger incorporates rockwool into its cavities. Completed with blocks for chaining, lintels, windowsills..., it meets the RT 2012 (24.8 xh 24.9 x 36.5 or 42.5 cm, R = 4.66 or 5.5 m².K / W, 14.7 to 17 kg the block).

cellular concrete window sill

Barrier against air and water, window sills made of aerated concrete have a good isothermal. They adapt, moreover, to all the constructive modes.

non-seasoned sandwich panels

Made of an insulation with a tight vapor barrier between a decorative underside and a waterproof particle board exterior facing, these non-seasoned sandwich panels are equipped with two contréliteaux.
They arise in the direction of the slope or its perpendicular.

tile support plates

Quick to implement, tile support plates ensure a reinforced sealing of the roof. They resist to strong winds and are used from 9% of slope.

More insulating, less resistant

Energy saving and competition of the ecomaterials obliges, constructive systems associate lightness, glued laying and thermal insulation. Some are type "monomur" with substantial thicknesses (30 to 45 cm). Like brick all-in-one or cellular concrete, they have their limits: thickness reducing the living space, thermal performance lower than the RT 2012 making a reported insulation necessary. Finally, their mechanical strength limits the height of structures, with the exception of the expanded slate block.

double prefabricated sponge

The double row of prefabricated sponge evokes traditional Provencal architecture while avoiding the presence of a gutter.

wall cladding

This wall cladding restores the grain of the limestone, while on the ground a pavement lets the light play on the irregularity of its surface.

RT 2012: the waste hunt

RT 2012 aims to divide by three the energy consumption of new buildings. The heating bill can go from 250 € / year for a house "low consumption" to 1,800 € for a poorly insulated house.
To achieve this, there should be no thermal bridge on the floors. Essential, the low floor on crawl space must ensure a total continuity of the insulation, by disconnecting the slab of the peripheral walls and rests.
In terms of materials, the most common solution uses thermal breakers, interstices and abutments made of expanded polystyrene, concrete blocks and insulated planars compliant with RT 2012.

portal frame with reconstituted stone kit

To frame the portal, reconstituted stone kitscomposed of bushels and capitals, imitate natural stone or brick offering an authentic mineral aspect.

climb a staircase with modules

The assembly of this staircase consists of stacking the modules forming the central shaft and, in parallel, to fit the steps (with respect to the shaft) glued with a polymer mastic. The end of the steps is supported while the central shaft is scraped and filled with concrete.

spine staircase

"Spine" of this stay, this spiral staircase is molded in concrete (crushed limestone, white cement, pigments...).


Prefabricated staircase models are divided into two categories. "Monoblocks", which are transported by truck and are positioned by means of a hoist. And the stairs "kit" based on stacked steps, which amount in two days maximum. It is enough to superpose boulder blocks to form a keg in which concrete will be poured after reinforcement. The steps are recessed cantilever in the reservation of each element of the barrel. Concrete can be left raw, treated (smooth, polished, waxed...) or receive various floor coverings (natural stone, terracotta...).

Two building materials under a magnifying glass

monomur brick

Cellular concrete:

many advantages Light but strong, cellular concrete consists of dry sand, lime, cement, gypsum and aluminum, then baked under pressure at 190° C. Five times lighter than concrete, it is easy to handle and easy to install. Thanks to the microbubbles of air which it contains, it is a good insulator (conductivity L = 0,09 W / m.K in 25 cm of thickness), whose inertia attenuates the differences of temperature. However, the evolution of thermal stresses (RT 2012) requires building with blocks 50 cm thick (R = 5.5 m2.K / W) or provide additional insulation (25 cm block + thermo-acoustic complex). Add the need to coat the entire wall.

The monomur brick:

the integrated insulation Thickness of 37.5, 42.5 or even 50 cm, the monomur brick accumulates the heat of the day to restore it at night. It traps the ambient air thanks to a network of vertical cells. The temperature remains cool in summer and stable in winter thanks to its high inertia. The construction of the walls (which excludes any reported insulation) is done in a single operation. Nested dry, its installation is done with a mortar-glue. The disadvantages of this brick are its thermal performance that no longer meet the requirements of RT 2012. Its resistance (R) is 4 m2.K / W for a thickness of 42.5 cm. What is below R = 5 m2.K / W required in new construction. Moreover, its weight (from 250 to 320 kg / m2 depending on the thickness) requires solid foundations and concrete links that weigh down the bill. Also, manufacturers are proposing bricks whose cells incorporate an insulation that meets the RT 2012.

Video Instruction: Updating Your Deck with New Composite Decking Boards