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Sheet materials are structural and non-structural panels engineered from both solid timber and recycled timber using different types of adhesives.
The most widely used products in construction are plywood, medium density fibreboard (MDF) particleboard (chipboard) and oriented strand board (OSB).
A versatile building material with a wide range of applications, from wall and floor sheathing, to designer interiors and glider fuselages. This Topic deals mainly with structural plywood.
Softwood plywood is usually made from European spruce and mainly used in construction. Hardwood plywood is usually European birch, with clearer grades available for decorative use.
It has good weather resistance and strength properties in compliance with specific standards such as BS EN 13986 (plywood in marine use), rather than the structural standard code Eurocode 5, and should not be used structurally.
Marine plywood must have third party accreditation to demonstrate full compliance with BS 1088: 2003 Marine Plywood. See the TTF guide to Marine Plywood.
Durability, glue bond performance and resistance to decay may have to be considered, if not appearance and strength. Suitable sheets are available from Scandinavia, North America and the Far East.
Plywood for structural loadbearing applications, such as walls, floors and roofs, must be strong enough for the loading. Always use plywoods listed in Eurocode 5, which typically comes from Sweden, Finland, America or Canada.
They must also comply with the Construction Products Regulation (CPR) by meeting the requirements of BS EN 13986, or by other means.
Must carry the CE mark to demonstrate CPR compliance and fitness for a particular purpose.
Spruce plywood is ideal as a roofing membrane, strong, light-weight, easy to handle and fully compliant with Eurocode 5. Precisely dimensioned, the panels are easily converted into durable surfaces, such as the foundation for the construction of moisture barrier roof structures.
They can also be fitted together to form safe working surfaces while the roof installation is being carried out. In attic spaces, the foundation panels can be left uncovered.
Fitting plywood sheets to roof trusses to form a solid base for battens is known as sarking. It results in a robust roof structure that is particularly popular in Scotland.
The most common types of plywood available for use in UK construction are structural plywood for humid uses (EN 636-2 S) and general plywood for humid uses (EN 636-2 G). These types of plywood are made from durable resins that are suitable for most construction uses.
A stiff, flat, engineered sheet made of wood fibres, bonded with resin. It has a consistent surface, without grain or knots and can be machined, drilled, cut and filled easily without damaging the surface.
It is available in finished products, such as skirting boards, architraves and other mouldings, and as Fire-rated and external grades. It is sometimes colour-coded by dyes in the board layers:
When used in construction, MDF must comply with Construction Products Regulation (CPR).Always wear a facemask when sanding wood – especially MDF.
Particleboard, or chipboard, is made from wood chips, often recycled, compressed together with resin to give a smooth, knot-free surface.
Different grades and thicknesses are available for use in a variety of structural and non-structural applications.
Resin-bonded sheets of thin strands of wood, compressed into layers to form a mat, giving good dimensional stability with no knots or voids.
Different grades and thicknesses are available for use in a wide range of structural and non-structural uses.
BS EN 13986:2004 Wood-based panels for use in construction. Characteristics, evaluation of conformity and marking, BSI
BS EN 622-5:2009 Fibreboards. Specifications. Requirements for dry process boards (MDF), BSI
BS 5268-2:2002+A1:2007 Structural use of timber. Code of practice for permissible stress design, materials and workmanship, BSI
BS 1088-1:2003 Marine plywood. Requirements, BSI
BS EN 300:2006 Oriented strand boards (OSB). Definitions, classification and specifications, BSI
BS EN 312:2010 Particleboards. Specifications, BSI
BS EN 636:2003 Plywood. Specifications, BSI
BS EN 314-2:1993 Plywood. Bonding quality. Requirements, BSI
DD CEN/TS 1099:2007 Plywood. Biological durability. Guidance for the assessment of plywood for use in different use classes, BSI
Timber is the most sustainable mainstream building product. It is naturally renewable. Over 90% of timber used in UK construction comes from Europe, where more trees are grown than harvested (source: TTF Statistical Review 2016).
Softwood and temperate hardwood forests in Scandinavia, Europe, Canada and North America are stable or growing. Growing forests act as carbon sinks; wood products act as carbon stores.
Ask for PEFC or FSC Chain of Custody certification.
See Wood Campus RIBA CPD module Procuring Sustainable Timber for more on timber certification and sustainability and government requirements.