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In this section, you may consult information about roofing, cladding, our product lines as well quality and performance standards of materials.

Table of contents

and certifications
A few indications
for building

A: standards and certifications


The “Document Technique Unifié” (DTU) is a document which establishes material standards for any building works in France. It is established by the « Commission Générale de Normalisation du Bâtiment/DTU » and defines the conditions under which construction materials must be used.

A DTU is generally made of the following documents:

  • A "cahier des clauses techniques" (CCT) which defines the rules for choosing and using various materials
  • A "cahier des clauses spéciales" (CCS), attached to the CCT which defines the limits of services offered and various obligations towards other professions
  • General calculation rules for the size of works to be accomplished.

These three types of documents have a contractual application. There are other documents such as mementos and choice guides, which can come into play – these are useful when designing the works but are not part of the actual contract.

The DTU does not have a proprietary website, but various forms of DTU’s may be purchased from the CSTB website ( or from the AFNOR (

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CSTB approbation

The "Centre scientifique et technique du bâtiment" (CSTB) is a French public service which contributes greatly to quality and security in construction works. It namely delivers technical approbation which act as a guarantee for the quality of the products and defines their common use.
CSTB approbation acts as quality assurance and enables users to obtain insurance coverage if usage conditions defined in the approbation memo are correctly implemented.

For more information, visit the CSTB

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1200 joules standard

The 1200 joules standard certifies that roofing material will resist a 70Kg object falling from a 1 metre height. This standard is often required for new constructions.

Here is an example of a test on one of our skylights, one minute after we dropped a bag on top – the tests show the bag did not go through the skylight.

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Resistance to fire classification

In France, there is a fire-resistance classification which defines 6 categories for materials :

  • M0 " incombustible "
  • M1 " non inflammable "
  • M2 " hardly inflammable "
  • M3 " mildly inflammable "
  • M4 " easily inflammable"
  • M5 " very easily inflammable"

These standards are progressively being replaced by European Standards – for construction products, these classifications are :

  • A1, A2, B, C, D, E, F (for inflammable potential)
  • s1,s2,s3 (for smoke)
  • d0, d1, d2 (flaming droplets and particles).

Here is the corresponding table:

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Simplified smoke extraction standards

Smoke extraction from buildings and air circulation can happen through:

  • Natural smoke extraction
  • Mechanical smoke extraction

For air vents and staircases, a third solution is sometimes allowed:

  • Smoke containment

Whatever the technical choice, smoke extraction always consists in an air “push” on one side and an air “pull” on the other (the opening) which creates the necessary draft conditions for smoke extraction to occur.

In France, the “instruction technique n° 246 du 22 mars 2004” gives indications on the necessary conditions for a successful smoke extraction to occur (size, amount of ventilation required…), and the NF S 61-93x standard explains which materials are required to match appropriate levels of smoke extraction capacity.

Smoke always accumulates in the higher parts of a building and the smoke evacuation therefore always occurs off:

  • Rooftop outlets
  • Façade openings
  • Manholes connected to the ventilation system

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Snow and Wind standards

The NF P 06-002 standards or the NV 65 rules define the effects which snow and wind can have on constructions. They analyse the impact of wind and snow to take into account when building roofs.

The impact of wind on the components of a roof are taken into account following several criteria:

  • The zone where the building is situated – France is divided into 4 zones and each zone is given a different wind speed index
  • The environment where the building is situated – the standard defines four types of environments (urban, small towns, countryside, lakeside or seaside...)
  • The height of the roof - the distance from the top of the roof to the ground level is measured and the higher the rooftop, the more the impact of the wind – there are five height categories
  • The roof side slopes.
  • The position of the roof in the construction – if, for instance, the roof may receive extra snow from a higher adjacent roof, then the anticipated snow load must be raised. Similarly, if the shape of the roof and/or its position favours the accumulation of snow.

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B: Thermal performance

Various insulation coefficients

Each material carries different insulation properties. The most used coefficients are R (thermal resistance) and U (surface thermal transmission):

  • Thermal transmission (U) measures the propagation of heat through a 1m thick material for a temperature difference of 1°C between each side of the material. It is measured in W/m.K, a value which allows us to quantify the insulating capacity of each material.
    The lower the U, the higher the insulating performance.
  • Thermal resistance (R) quantifies the insulating capacity of a material for a given thickness and is measured in M2.K/W – the higher the R, the higher the insulating performance.

With respects to roofing or cladding materials, the most common measure is U which you can find on all Dhaze products.

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The coefficient U (surface thermal transmission)

The surface thermal transmission coefficient is most often used to define the thermal resistance of a wall, is measured in W/m².K, and measures the heat flux through 1m² of wall. Therefore, the lower the U, the more insulating the wall is.
The U coefficient is increasingly used to measure the performance of roofing materials than the R coefficient or others.

The figure below shows that insulation is far better with 55mm structured polycarbonate than with 16mm structured polycarbonate.

U = Surface thermal transmission coefficient

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The most insulating products of the Dhaze product line

Illumination products

Roofing products with opaque cladding

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C: Plastic materials

The difference between PVC, Polyester and polycarbonate


Polycarbonate material is made of a polycarbonate resin (thermoplastic resin), treated on one side against UV rays using a co-extrusion methodology. Polycarbonate is marked by a very high resistance to shocks, clearness, flexibility and excellent longevity.

Polyester: <

Polyester panels are made up of polyester resin and reinforced with fibreglass and an anti-UV treatment is then applied.
Resistant to corrosion (acids, grease, detergents…), they also resist to temperature changes. However, polyester is less clear and transmits lights less efficiently than Polycarbonate of PVC.


PVC panels are made up of polyvinyl chloride and have an anti UV-ray treatment in the main body (hence efficient on both sides). PVC has a high value for money and has an excellent resistance to fire rating (M1). The temperatures of use are slightly more limited than polycarbonate (-20°C to +60°C).

Different finishes for structured polycarbonate

  • Clear: transparent finish – shapes and colours are discernable through the panels.
  • Opal: transparent finish – shapes and colours are not discernable through the panels but light is diffused.
  • Reflex: transparent finish with visual properties similar to opal but one side reflects sun rays to avoid overheating in the summertime.
  • Gold: reflects and returns a very high proportion of sun rays, thereby limiting overheating and regulating the amount of light which penetrates through the panel.
  • Blue Spring: cspecial blue layer, co-extruded on the outside surface which attenuates sun rays greatly and limits room temperature whilst letting a maximum amount of light through.

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Different polyester classes

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D: A few indications for building


Reach is the maximum allowed distance between rests for a given profile, panel or plate (Figure 1).

Fig. 1 Fig. 2

If you go beyond the defined reach, the panel, profile or plate may bend (Figure 2).

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Minimum slope

Slope is an important part of building a roof for the following reasons:

  • Keeping the roof watertight: the steeper the slope, the less water will be able to infiltrate your roof due to a lessened capillary action
  • Calculating the structure: the steeper the slope, the less resistance is required to say, an extra weight of snow

For structured polycarbonate, a slope of at least 12% is advisable

For a steel plate roof, a slope of at least 10% is advisable

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Number of bindings

Structured polycarbonate roof:
For Dhaze profiles with tightening bonnets, we recommend one screw every 30cm for all polycarbonate thicknesses (16mm, 32mm or 55mm)

Steel plate roofs:
For dry, regulated or insulates steel plates, we recommend 4 to 5 bindings per m². For dry, regulated or insulated tiled steel plates, we recommend 8 bindings per m².

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Overlap is the transversal overlap between two insulated steel plates or two multi-skin polycarbonate plates. It is important to define the size of this overlap as well as the direction in which the panels are laid (left or right).

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