The optimal resistance of a wood clear finish system does not only depend on the proper performances of the finish but also on the dimensional stability of the substrate. The improvement of durability for such a system can be achieved by modifying the wood surface. For example, we proposed to form a wood/polymer composite via a photochemical process before application of a topcoat. The use of simplified model formulations enabled us to show that the improvement of adhesion durability is related to both the interaction energy between the surface composite and the topcoat and the flexibility of the surface composite itself. The improvement of the formulations used to form the composite appears rather critical because of the specific behaviour of each species. This specificity arises from the influence of the phenolic extractives onto the radical curing reaction.