Abstract: This invention relates to methods and apparatus for successively dispensing predetermined quantities of urea formaldehyde foamed resin mixture having as constituents a resin component and a hardener component in which a prefoamed one of said components and the other component are independently fed under pressure to a mixing chamber where they are mixed and from which, they are dispensed, any residue of the urea formaldehyde foamed resin mixture left in the mixing chamber after said predetermined quantity has been dispensed therefrom being swept and removed prior to the mixing chamber being supplied with the next batch of said components.The present invention is particularly useful for filling pre-cast cavity building blocks with insulating foamed material.