While zinc has been used to clad the exterior of buildings for over two centuries, the number of options on offer has increased considerably, especially in recent years. The most obvious of these choices revolves around the finish of the zinc. Natural zinc is frequently used for traditional batten cap Parisian roofs, but is less common in the UK and Ireland where pre-weathered zinc is more frequently specified. Pre-weathered zinc ranges from middle grey QUARTZ-ZINC to darker ANTHRA-ZINC, as well as a range of zinc with a discrete colour added to the pre-weathering. Seven standard finishes now exist in the PIGMENTO range. Finally, engraved AZENGAR is yet another option for consideration. Zinc performs very well in all climates, including coastal locations. The darkness of ANTHRA-ZINC means that the aspect can evolve by the sea, and here ANTHRA-ZINC STRAT should be considered. Non corrosive staining is possible on all zinc surfaces that are not rinsed by rainwater but are close to the sea, for example soffits.
Next, the required panel aesthetic must be considered. For roofing the choice is mostly limited to long panels joined using a 25mm standing-seam or a timber batten flashed with a zinc cap. Both these systems must be installed at a minimum as built slope of three degrees; indeed all metal is not a flat roof material. For slopes above 14 degrees, the diamond ADEKA shingle can be used. This panel gives more of a textured aesthetic and requires nine tiles per square metre.
The number of options for walls is far greater, with flat lock, recessed joints and obviously standing-seam joints all being possible. Panels can also be linear, both horizontally and vertically installed, but also orientated at an angle and square- or diamond-shaped. Again, zinc wall cladding can be used in all environments. However, for exposed sites panel dimensions may have to be decreased and zinc thickness increased. Another important consideration is flatness. Metal facades will never be completely flat, but some systems will perform better than others. For example, a rainscreen using 300mm wide Interlocking panels will offer a flatter finish than a standing-seam facade.
Both wall and roof build ups are critical. Traditionally, zinc roofs have been installed on vented timber substrates and this is still a completely acceptable construction method. However, for several reasons warm roof non-vented build ups are becoming more common. Warm roof construction improves air tightness and reduces thermal bridging. It also allows the main elements of the roof to be non or of limited combustibility following EN13501, A1 and A2. It should be noted that both vented and non-vented roofs are covered by BS 476-3 and CEN/TS 1187 Brooft4 for no flame penetration or spread. Where the core materials used in a facade must be A1 or A2, which is typically the case for residential buildings above 11 metres in height, plywood should be avoided and can be replaced with metal decks and/or rails depending on the zinc system being used. Combined with a mineral board insulation and appropriate fire stops, a compliant facade can easily be created.
The long history of VMZINC provides examples of projects where the zinc has been in place for over 100 years. This project data is supplemented by the BRE EN15804 Environmental Product Declaration that references a service life of 100 years. A durable material with limited maintenance needs not only correct design but also appropriate installation. Since 2014 VMZINC have been operating the VMZINC@WORK partner program. The program supplies added training to already skilled hard metal contractors thus further driving up quality and workmanship.
If you would like any further information including samples or an online RIBA accredited CPD please call 0203 445 5640, email or visit the VMZINC website.