In a method for manufacturing conglomerate articles in sheet form, a mix comprising the following is prepared: an expanded inert granular material; a filler consisting of hollow inorganic microspheres and a plasticizer (clay, quartz or other powder mineral, cellulose); an aqueous silicon-containing binder. A layer of mix, where necessary coated with a fibreglass meshwork in order to increase the mechanical strength thereof, is deposited on a temporary support and subjected to vacuum vibrocompression. The resultant rough-formed sheet is heated at a controlled temperature so as to cause evaporation of the water present in the mix. A light, sound-absorbing, heat-insulating sheet, rated in Class 0 in terms of fire reaction, suitable to be plastered or painted superficially and used for forming panels and partitions for internal and external use, is obtained.