Moisture conditions in timber cladding: field trial data for Sitka spruce

I Davies, Charles Fairfield, Alastair Stupart, P Wilson

Research output: Contribution to journalArticlepeer-review


Exposure trials on timber cladding are valuable for informing facade designers. This paper describes a trial using Sitka spruce (Picea sitchensis). Sitka spruce is the only UK-grown timber available in sufficient volume to supply the growing cladding market, but its suitability is unclear. Data indicated that the moisture content range in timber cladding was wider than generally accepted. The minimum of around 10% moisture content appeared to be similar for all details tested. The maximum was influenced by construction detailing but was around 30%. From a theoretical standpoint, the range, and rate, of moisture content fluctuation observed meant that the commonly quoted average value was largely irrelevant. The mode was a more representative statistic; most of the data were skewed towards the wood's fibre saturation point. Sitka spruce is, therefore, at risk of fungal decay and is only suitable as external cladding in the UK if treated with preservative.
Original languageEnglish
Pages (from-to)263-278
Number of pages16
JournalProceedings of Institution of Civil Engineers: Construction Materials
Issue number5
Publication statusPublished - 2012
Externally publishedYes


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