The consolidation of 5 building materials is investigated: Tuff of Maastricht, Avesnes, Euville, Balegem, and Gobertange. Small and large samples can be consolidated by impregnation witha 50/50 mixture of methyl acrylate/ethyl methacrylate at which 1 mol % initiator is added. The temperature should be at least 65°C, for larger samples 80°C. Good results can also be obtained by radical polymerization of polyesters. Experiments with gamma-irradiation showed that in many cases cracks are obtained, and that the best way to avoid these is by adding initiators to the monomer mixture and by working at high dose rates.