VMZINC and water

In general, the presence of water inside metal roofing and cladding complexes accelerates corrosion and thus reduces the life span of the work.

VMZINC reacts to the main components of the atmosphere particularly in the presence of H2O (water), SO2 (pollution), NaCl (sea spray) and CO2 (CO2).

The first reaction of titanium zinc to oxygen and water is the formation of zinc hydroxide Zn(OH)2, which, when there is sufficient concentration of CO2 in the air, allows the protective layer of patina or zinc hydroxycarbonate to form.

It is therefore important that the surfaces of the VMZINC are ventilated so that there is a sufficient supply of CO2 to allow the formation of the protective patina. This applies particularly to the underside of the VMZINC.

VMZINC PLUS is a unique solution that consists of rolled titanium zinc, with a protective coating on the underside. The 60 micron thick organic coating is applied in the factory. VMZINC PLUS, meets the requirements related to a lack of sufficient ventilation of the underside of the titanium zinc.

This product is mainly intended for warm roof applications, where an insufficient supply of CO2 to the underside of the titanium zinc prevents the formation of the patina. It is also intended for solid wood or reconstituted panels the compatibility of which is compromised by the type of treatment.

To allow a good ageing of VMZINC PLUS and the other roofing components, it is important to limit the amount of water which may condensate on the VMZINC PLUS underside.

These conditions are achieved by:

• The installation of a watertight VMZINC roof preventing any rainwater or snow leakages during the installation or the service life
• The use of vapor retardant and/or waterproof membranes to limit the transfer of water vapor from inside the building.

In some specific conditions, VMZINC PLUS should be used with VMZINC DELTA membrane.

For information on the use of VMZINC PLUS and VMZINC DELTA, please consult your VMZINC office.

Snow loads

In areas where roofs are exposed to snow falls, cycles of freezing / melting contribute to the transformation of the snow into ice which results in:

• an increase in the snow density
• an increase in the hydrostatic pressure of the water trapped inside the transformed snow, thus compromising the water tightness of the roofing systems either by simple infiltration through overlapping elements, or by increasing capillary action through crimped components.

Therefore, special design should be chosen in order to control such constraints.

For information on the roofing designs adapted to snow falls exposure, please consult your VMZINC office.