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Author(s): Brandt, E. and Hansen, E. J. P.
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: 328-335
Total Pages: 8
Language: English

Abstract: In Denmark water tightness of roof underlays is of great importance as the underlay serves as the final barrier against water ingress in roof constructions. A popular trend is pitched roofs with ceilings parallel to the roof surface leaving no or very poor accessibility for inspection and repair of the roof underlay.

Roof underlays used in Denmark are to a large extent based on flexible polymer sheets or fibre boards with a coating on the upper side. The underlays are not supported by a rigid underlay.

The durability of the roof underlay is crucial in order to maintain the water tightness for the entire service life of the roof covering. Especially taking into consideration that there is a frequent use of clay tiles and similar where wind-driven rain has fairly easy access to the roof underlay. Also, some clay tiles allow a relatively high amount of solar radiation to pass through the corner joints thereby allowing degradation due to UV light.

The paper presents results from testing of water tightness of different types of roof underlays including a wood fibre board and a gypsum board. Results are mainly from test specimens of nine different roof underlays which were exposed to in-use conditions in a test house at the Danish Building Research Institute. Specimens at the test house were exposed to the south and to the north respectively. These specimens have been exposed for about 18 years. The results from the test house are supplemented by results from a small number of test specimens taken out from buildings after some years of service.

The results of the investigations are that a major part of roof underlays commercially available in the 1990ies degrade considerably in-use thereby losing its water tightness.

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

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