Particleboard is manufactured from wood particles and resin, and when used for construction in the UK it is a legal requirement that the manufacture, specification and use be according to a European Technical Specification, principally EN 13986. This specification in turn refers to BS EN 312, which specifies seven grades of board according to the intended use, properties and environment ( dry or humid ). The four loadbearing grades are specified according to their mechanical properties ( 5th percentile ) and moisture resistance ( 95th percentile ). Grades P5 and P7 are recommended for flooring applications because of their moisture resistance. Prototype testing of floors, walls and flat roofs, and structural design by calculation are briefly discussed.