Moisture performance properties of exterior sheathing products made of spruce plywood or OSB

Tuomo Ojanen, Jarkko Ahonen

    Research output: Book/ReportReport


    Plywood and OSB (Oriented Strand Board) are building boards that are made of timber and glue and that have good structural strength. OSB is a relatively new product that is produced from various timber materials and even some wastewood can be used as raw material for this product. Due to the easy access of raw material and economical reasons, the use of OSB has been highly increasing. The moisture safety of the building envelope depends on the properties of the building products. The moisture performance properties of the sheathing boards have not got enough attention, too often these wood based materials are equated without considering the real properties and their effect on the overall moisture performance. This research was carried out to experimentally determine the material properties and performance characteristics that have an effect on the moisture performance of building structures where OSB or spruce plywood are applied as exterior sheathing boards. A relatively representative amount of samples were used to study the moisture properties of European OSB and plywood products and a comparison to one Canadian OSB and one plywood product was done. All the products used in this research were meant to be used also as exterior sheathing boards. The results shows clearly the differences between OSB and plywood products. The products are not interchangeable. The main differences can be found from the vapour permeability levels that have an effect on the drying efficiency of building structures. The products have different performance criteria, and the climate conditions and moisture loads have to be studied to evaluate their suitability and moisture safety aspects in different applications. Water repellent features and drying efficiency are somewhat opposite properties of the products and the dimensional changes under varying moisture contents can set some boundary conditions when the optimum solution for the exterior sheathing is considered.
    Original languageEnglish
    Place of PublicationEspoo
    PublisherVTT Technical Research Centre of Finland
    Number of pages65
    ISBN (Electronic)951-38-6572-X
    Publication statusPublished - 2005
    MoE publication typeNot Eligible

    Publication series

    SeriesVTT Working Papers


    • building envelope
    • material properties
    • moisture content
    • drying efficiency


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