Zinc Roofing Warm vs Cold Roofing
8 April, 2020
On the face of it, it might seem like an odd comparison, but there is a choice to be made between a cold roof and a warm roof, and this article will look into the reasons to consider each option for Zinc Roofing.
Warm Roofing
The main advantages are air tightness, speed of installation and simplified roof detailing. Installation can be on a steel or timber deck; the deck is then covered with a bituminous vapour barrier with a high-water vapour resistance installed with adhesive/primers. The vapour barrier is crucial on a warm roof construction, with the following brands typically used Warmfast, Metvap and Alutrix 600.
Mineral Wool or PIR Insulation is installed on the Deck/Vapour barrier using a plug and screw method with the vapour barriers self-healing qualities maintaining its durability and duty.
A Breather Membrane/Structural underlay is rolled over the insulation in preparation for zinc to be installed, Products typically used VM Zinc Membrane Pro, RZ Vapozinc, Tyvek-Supro, ISO-Mat, Klober Permo and Metmat.
Zinc Panels are installed to the prepared deck using Fixed/Sliding Clips with Plugs and Screws specific for warm roofing. Products typically used are Warmfast and Thermoseam and the setting out of the fixed/sliding clips is to specific manufacture guidelines.
To note: Specific Product, Detailing and Installation recommendations mentioned above will vary for each separate Zinc Manufacturer. Please see below typical VM Zinc Warm Roof Build-up for Standing Seam Roofing taken from the May 2019 Standing Seam Design and Specification Requirements Literature.
Cold Roofing
The main advantages are that it provides excellent pull-out resistance and a continuous rigid deck to install.
A cold roofing substrate requires a 50mm continuous air gap beneath the support of the Zinc, this is to allow ventilation throughout the roof area. The warm air created from within building through heating, breathing and cooking meeting the cold air from the environment forms moisture which can cause rot, damp and even structural damage to your roof. By installing the ventilation path this will eradicate and clear the moisture build up as air travels throughout the space.
Installation of the Insulation and Vapour Barrier is completed within and below the rafters allowing these works to progress internally. A Breather Membrane is rolled over the Rafters/ Insulation, products typically used VM Zinc Membrane Pro, Tyvek-Supro and ISO-Mat.
50mm Ventilated space is created typically by using 50x50mm Timber battens installed to the rafters running from eaves to ridge. 18mm Plywood installed to battens with a second breather membrane rolled onto the plywood prior to Zinc.
Zinc Panels are installed to the prepared deck using Fixed/Sliding Clips using nails/screws to fix.
To note Specific Product, Detailing and Installation recommendations mentioned above will vary for each sperate Zinc Manufacturer. Please see below typical VM Zinc Standing Seam on Vented Plywood taken from the May 2019 Standing Seam Design and Specification Requirements Literature.
Salmon Solutions are proud to be a leading provider of the highest quality roofing in South East England. From zinc and single ply roofing to aluminium and lead roofing, our experts are fully accredited and experienced in the installation, maintenance and repair of roofs of all types, shapes and sizes. For more information, please get in touch with us today.
