Moisture conditions in external timber cladding: field trials and their design implications

Davies, Ivor (2011) Moisture conditions in external timber cladding: field trials and their design implications. PhD thesis, Edinburgh Napier University.

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    This thesis describes the development of technical guidance on timber facade design.
    The study involved a state-of-the-art review; an exposure trial of external cladding
    made from Sitka spruce (Picea sitchensis) and the production of construction details
    and associated information. It was undertaken because timber is an increasingly
    common cladding material in the UK, being used on low-rise residential buildings and
    for medium-rise and non-domestic buildings. The risks have, therefore, increased but
    this is not reflected in published guidance. Sitka spruce was used due to its
    availability in the UK and its similarity to Norway spruce (P. abies) which is widely
    used for cladding in Scandinavia.
    The exposure trial indicated that the moisture content range in timber facades is wider
    than accepted. The minimum moisture content of around 10% appears to be similar
    for all types of timber cladding and all species. The maximum appears to vary
    between species according to their fibre saturation point and is influenced by
    construction detailing and workmanship. A preliminary model of these interactions is
    From a theoretical standpoint, the moisture conditions observed in the trial mean that
    the (commonly quoted) mean moisture content is all but irrelevant. The mode is a
    more representative statistic as in most cases the data are skewed towards the fibre
    saturation point for the species concerned. Most detailing combinations had a
    moisture content near to the fibre saturation point throughout the winter. Sitka spruce
    is, therefore, only suitable as external cladding in the UK if preservative treated.
    Around 40 construction details were produced. They integrate, for the first time, all of
    the performance requirements applicable to low- and medium-rise timber facades in
    the UK. The work’s key benefit is that the guidance arising from this study
    rationalises and improves facade design. Further research is, however, needed to
    validate the moisture content model and extend it to other timber species.

    Item Type: Thesis (PhD)
    Uncontrolled Keywords: Timber facades; Sitka spruce (Picea sitchensis); timber cladding; moisture; technical guidance;
    University Divisions/Research Centres: Faculty of Engineering, Computing and Creative Industries > School of Engineering and the Built Environment
    Dewey Decimal Subjects: 600 Technology > 690 Building & construction > 698 Detail finishing
    Library of Congress Subjects: T Technology > TH Building construction
    Item ID: 4702
    Depositing User: Ivor Davies
    Date Deposited: 01 Nov 2011 11:16
    Last Modified: 31 Oct 2013 01:38

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