With high physical and mechanical performances, especially in bending, plywood is particularly well adapted for the construction of load bearing floors.
The panels intended for the construction of load bearing floors must be in conformity with the requirements given in EN 12871 "Wood-based panels - Performance specifications and requirements for load bearing boards for use in floors, walls and roofs". Only the "S" marked panels (structure) may be used for this application. These panels must bear a CE marking corresponding to products for structural use (CE 2+).
The general rules for the installation of the panels are described in the French standard DTU 51.3 " Timber floors or wood-based panels floors".
In the absence of a risk of eventual humidification, the use of bonding class 1 (EN 636-1) panels is possible. But in cases where there is a risk of moisture returning, a panel with bonding class 2 (EN 636-2) for interior humid conditions or class 3 (EN 636-3) for exterior conditions is recommended.
The minimal thickness to use depends on the span between supports and on the mechanical characteristics of the product used.
In each case, the calculation of the dimensions of a load bearing floor must take into account the characteristic values of the panels provided by the manufacturer.
By way of example the tables below indicate the maximum spans (from one axis to the other) calculated by taking into account a deflection of 1/400 of the span for a distributed load in humid conditions (service class 2).
The calculation does not take into account any possible concentrated or dynamic loads and the floor covering must not exceed a load higher than 7 kg/mē.