What is a cold roof?

A cold roof is where a waterproofing membrane is applied on top the structural deck, typically on top of a separation layer.

The Vapour Control Layer (VCL) and Thermal Insulation are installed within the structure – their positioning and installation are crucial to the overall success of this type of roof structure.

Above the Thermal Insulation and VCL unimpeded cross flow ventilation in line with current Building Regulations guidance must be created to ensure that any warm moist air that travels through the roof package is blown through structure. Failure to provide adequate cross flow ventilation will allow warm moist air to condense on the underside of cold structural deck, thus creating interstitial condensation. 

Design Considerations

The design of cold roofs usually occurs when external abutment height provision is problematic, thus making a warm roof not achievable. Sika’s experience would be to avoid cold roof design where possible. Cold roofs are generally considered as difficult to design and construct and future upgrading of insulation requires invasive destructive means which should be kept in mind.    

All Sika membrane systems Sika-Trocal and Sika Sarnafil (single ply membranes), Sikalastic (liquid applied membranes) or SikaBit (bitumen membranes) can be considered for use when creating cold roof constructions, selecting the particular system will depend on each project design brief.

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