substantial advantages of both a technical nature and economical of a technical nature since it becomes possible to form dome like building structures with diameters equal to or exceeding 40 meters 131 feet even at particularly ill served sites without prejudice for the reinforcement and casting accuracy and this because the amount of concrete to be spread at the ground rapidly i e before part of the concrete loses its required fluidity is considerably reduced owing to the cited small thickness of the first dome portion and because the second dome portion being formed after the membrane has been inflated may be reinforced accurately and formed concurrently with the edges and beads for the openings desired of an economical nature thanks to the lower material and equipment costs and to the reduced and rationalized use of labor since the elastically deformable and self positioning reinforcement of the first dome portion is somewhat reduced and simplified and since the work is subdivided and no longer requires extensive concrete castings the above mentioned advantages are achieved and here resides an essential aspect of the invention by a method and its related apparatus for erecting dome like structures wherein the requirement for scaffolds and supporting falsework is either eliminated or minimized by virtue of the second dome portion being formed in direct superimposition over the first portion moreover it should be noted that.