Timber moisture content is a critical factor in adhesive performance.
Optimum timber moisture content for formaldehyde and epoxy adhesives lies in the range 6-12%. The maximum variation between adjacent pieces should be 2%, as moisture variation produces different curing rates for the adhesive. Casein adhesives can successfully bond timber with moisture contents up to 17%, but casein will degrade if this moisture content is maintained.
Thermoplastic adhesives are less sensitive to moisture content than are thermosets. PVA, animal glue and hot melt adhesives will tolerate moisture contents up to 17% while some construction elastomers will bond unseasoned timber provided the surfaces are dry.
Parquetry flooring is normally installed with a moisture content in the range 8-12% using a rubber latex adhesive.
Reference: Timber Datafile P11 – Timber Adhesives of the NAFI Timber Manual