Performance of Lower Pitched Metal Roofs

The Helfen Team have recently secured funding from BRANZ through the Building Research Levy to undertake a research project investigating how light and dark coloured metal roof claddings over low pitched roofs affect the management of condensation in roof spaces and to recommend solutions to improve air quality and durability of building elements in such spaces.

We have come across several properties with lower pitched metal roofs experiencing performance issues as a result of a build-up of moisture/condensation causing damage to various building elements. We have observed damaged or mould affected building elements including insulation, internal linings, intertenancy fire-walls, timber framing and building underlay. These issues have been seen in buildings of varying age, but at times have been seen less than 12 months after completion of construction.

Mould growth on building underlay and inter-tenancy fire wall in a relatively new building

Based on what we have seen to date, it appears that improvements in airtightness of cladding, joinery and wall assemblies generally has resulted in moisture loads from the interior of the building ending up in roof spaces, which in combination with the condensation that can occur on the rear of roofing metal, can result in moisture loads that the roof assembly cannot cope with. This appears to be contributed to by a variety of other factors, including inadequate moisture management both internally and within roof spaces, and the current trends towards both lighter coloured and lower pitched roofs.

During the course of the project we are interested to speak to anyone who has come across similar issues, both in relation to the cause of the problem and how it was resolved. We will in due course be publishing a report on our findings, but are more than happy to discuss the research with anyone interested in learning more about what we are doing or who has information to share that may assist with our project. We are also seeking assistance from industry in relation to the supply of materials required for the test sample, and any contribution of materials or assistance in that regard would be gratefully received.

Please feel free to reach out if you would like to discuss.

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