A pneumatic spring brake actuator, in particular a parking and service brake actuator for use in a commercial vehicle, said spring brake actuator comprising: - a housing comprising a housing base, - a spring brake piston accommodated at least partially in said housing, said spring brake piston being configured to reciprocatingly move between a retained position and an extended position along a longitudinal axis as a function of pressure inside a spring brake pressure chamber, - a compression spring located between the housing and the spring brake piston, said compression spring being effective to push the spring brake piston towards the extended position, characterized in that the spring brake piston comprises: - a service brake pressure chamber, - a piston chamber, and - a service brake piston separating the service brake pressure chamber from the piston chamber, wherein said service brake piston is configured to reciprocatingly move between a retained position and an extended position along said longitudinal axis as a function of pressure inside the service brake pressure chamber, wherein said spring brake piston comprises a front face, said front face being arranged opposite from said housing base, and a first pipe section extending from said front face towards said housing base, wherein said first pipe section radially limits said service brake pressure chamber and piston chamber, characterized in that the said spring brake piston comprises a second pipe section extending coaxially around said first pipe section, wherein said second pipe section comprises a radial protrusion abutting against a radial wall of said housing, wherein a volume between said second pipe section, said protrusion and said radial wall defines said spring brake pressure chamber. - a housing comprising a housing base, - a spring brake piston accommodated at least partially in said housing, said spring brake piston being configured to reciprocatingly move between a retained position and an extended position along a longitudinal axis as a function of pressure inside a spring brake pressure chamber, - a compression spring located between the housing and the spring brake piston, said compression spring being effective to push the spring brake piston towards the extended position, - a service brake pressure chamber, - a piston chamber, and - a service brake piston separating the service brake pressure chamber from the piston chamber, wherein said service brake piston is configured to reciprocatingly move between a retained position and an extended position along said longitudinal axis as a function of pressure inside the service brake pressure chamber, wherein said spring brake piston comprises a front face, said front face being arranged opposite from said housing base, and a first pipe section extending from said front face towards said housing base, wherein said first pipe section radially limits said service brake pressure chamber and piston chamber, characterized in that the said spring brake piston comprises a second pipe section extending coaxially around said first pipe section, wherein said second pipe section comprises a radial protrusion abutting against a radial wall of said housing, wherein a volume between said second pipe section, said protrusion and said radial wall defines said spring brake pressure chamber.