A household gas cooktop comprising: - a supporting and containing structure with an upper wall having an on-sight surface and a lower wall having outer sides which are upwardly bent and connected to said upper wall, - one or more support members arranged at said upper wall and defining a support plane for the containers to be heated, said support plane being on the side of the on-sight surface of the upper wall, - one or more combustion units arranged at said upper wall and being so configured as to generate flames in the space between said on-sight surface and said support plane, - a gas supply system (30, 31, 32, 33) so configured as to supply a gas flow to said combustion units, - a forced suction group adapted to suck a secondary air volume, - a ventilation duct which connects said forced suction group to said combustion unit so as to be able to supply said secondary air flow to said combustion unit, in which said ventilation duct extends at least partially on a lower side of the upper wall opposite said on-sight surface, in which said ventilation duct is connected to a plurality of combustion units and comprises an essentially plate-like single ventilation chamber and extending on all the combustion units of said plurality of combustion units, said ventilation chamber comprising a distribution wall defining a plurality of air outlet openings, each connected to a combustion unit, in which the combustion units comprise a diffuser which defines a plurality of gas outlet holes and a base portion which defines one or more distribution chambers (16, 17) adapted to distribute and convey the gas flow and the secondary air flow to said diffuser, in which said base portions of the combustion units form: - a secondary air distribution chamber, - a gas distribution chamber, - a tubular portion in flow connection with said secondary air distribution chamber, wherein said tubular portion is inserted in or over an edge of said air outlet opening of the distribution wall, wherein said distribution wall of said extended ventilation chamber comprises outer sides which are downwardly bent and said lower wall and said distribution wall define said extended ventilation chamber, characterized in that: - said upper wall and said support members and said base portions of the combustion units are formed in a single cast iron piece, - said upwardly bent outer sides of the lower wall are glued to the upper wall, - said downwardly bent outer sides of the distribution wall are abutting against the lower wall and a sealing gasket or a rubber tape is provided in a junction area between the distribution wall and the lower wall. - a supporting and containing structure with an upper wall having an on-sight surface and a lower wall having outer sides which are upwardly bent and connected to said upper wall, - one or more support members arranged at said upper wall and defining a support plane for the containers to be heated, said support plane being on the side of the on-sight surface of the upper wall, - one or more combustion units arranged at said upper wall and being so configured as to generate flames in the space between said on-sight surface and said support plane, - a gas supply system (30, 31, 32, 33) so configured as to supply a gas flow to said combustion units, - a forced suction group adapted to suck a secondary air volume, - a ventilation duct which connects said forced suction group to said combustion unit so as to be able to supply said secondary air flow to said combustion unit, - a secondary air distribution chamber, - a gas distribution chamber, - a tubular portion in flow connection with said secondary air distribution chamber, - said upper wall and said support members and said base portions of the combustion units are formed in a single cast iron piece, - said upwardly bent outer sides of the lower wall are glued to the upper wall, - said downwardly bent outer sides of the distribution wall are abutting against the lower wall and a sealing gasket or a rubber tape is provided in a junction area between the distribution wall and the lower wall.