The use of clay and wood waste in construction materials points out to a sensitivity to water, which is susceptible to reduce their durability. This work has first been interested in the influence of different constituents on the extreme dimensional variations (EDV) of such cementing composites. A formulation allowing the conciliation of environmental imperatives, interesting mechanical and thermal characteristics, and low density has been proposed. However, the EDVs remain above the required objective. In order to reach this value, different treatments have been examined. The addition of alkali-resistant fiberglass in the matrix did not lead to satisfactory results. Not only is the reduction of the EDVs insufficient for reasonable proportions of fibers, but this treatment also increases the proportion of absorbed water in presence of liquid water. Taken separately, both types of treatments used for wood particles - neutralization with hydraulic binders and extraction with boiling water of hydro-soluble compounds - also do not allow a sufficient reduction of EDVs. However, the combination of these two treatments allows the achievement of EDV1 mm/m. Such a treatment improves the mechanical resistance without significantly altering the thermal performances.Key words: wood concrete, extreme dimensional variation, fiberglass, neutralization, hydrolysis.[Journal translation]