DURABILITY PROBLEMS WITH ZINC CLADDED ROOFS DUE TO INPROPER UNDERLAYS

Author(s): Bunch-Nielsen, T. and Brandt, E.
Paper category: Conference
Book title: XIII International Conference on Durability of Building Materials and Components - XIII DBMC
Editor(s): Marco Quattrone, Vanderley M. John
Print ISBN: none
e-ISBN: 978-2-35158-149-0
Publication year: 2015
Pages: 737-743
Total Pages: 7
Language: English

Abstract: In Denmark the use of zinc as roof cladding has been popular among architects over the last 10 years, and a number of corrosion problems have occurred after less than five years in some of these roofs. It is corrosion from the back side of the zinc cladding and in most cases it is so called hot water corrosion due condensation on the downside of zinc. The underlays for the zinc cladding have changed over the years and the cladding is often layed directly on hard mineral wool or plywood with a thin underlay of diffusion open textile roof underlay, which is also used for clay tiles.

The corrosion is related to the moist environment between the zinc and the underlay and the lack of ventilation of the underside of the cladding and lack of protection from oxidisation of the down side of the zinc. The condensation is related to moisture in the underlays and the sub cooling from radiation to the sky on clear nights.

Bitumen corrosion from organic acids has also been used as explanation for some corrosion problems in zinc roofs when zinc is installed directly on an underlay of bitumen and the use of structured underlays are discussed.

The paper presents results from a number of inspections of zinc roofs in Danish environment and the laboratory test of the zinc plates and leaching of chemicals from the underlays.

New design of zinc roofs to prevent corrosion is suggested in the conclusion of the paper.

Online publication: 2015
Publication Type: full_text
Public price (Euros): 0.00