To propose a new construction method on a treating method of an existing metal frame among the reforming content of metal fittings such as a vestibule of a living multiple dwelling house by minimizing vibration, noise, dust and pollution.

A compromise construction method of two methods of removing the whole or finishing by screw-fastening by putting a new frame material on the existing metal frame D can perform rational reforming by integrating a new metal frame E and a sound part of the existing metal frame D embedded in a structure such as concrete by becoming solid infilling mortar when set by wetting by injecting dry mortar G and proper fresh water into a new metal frame reverse side void after sealing (H) a part by carefully fastening a small screw E12 by superposing a connecting margin E1 of the new metal frame E having the same opening dimension as the existing metal frame D and an existing frame connecting margin D15 of the obverse-reverse by taking away and removing the whole outside exposure part D16 facing the obverse-reverse of the existing metal frame D using a contact part of wall floors A and B and a part embedded in the structure such as the concrete of the existing metal frame D as the connecting margin D15 together with the infilling mortar.