Why the shaft matters
The shaft is the space the gas riser lives in for the life of the building. If it is badly planned, the riser can be hard to inspect, hard to ventilate and hard to keep safe. The PNGRB Gas Supplies to Multi Occupancy Residential Buildings Guidelines, 2020 set out what the shaft must provide.
A purpose-built, ventilated shaft
The riser should run in a shaft built for the purpose. The guidelines ask for ventilation, access at each floor and a shaft that is open at the top. The shaft must not be converted into a habitable room, and the riser should not run inside flats unless it is in a designed, ventilated shaft.
Access and floors
People must be able to reach the riser for inspection and maintenance at every floor. Where the shaft is continuous, a slab or similar floor is needed at each level, so that the shaft does not act as a chimney and so that work can be done safely.
Distance from electrical services
The riser should be kept at least 300 mm from electrical installations. Where a cable has to cross the riser, it crosses at a right angle with a 25 mm gap.
Movement inside the shaft
The riser is designed for expansion, contraction, sway and settlement, so the shaft must leave room for the pipe, its supports and any loops or guides. A shaft that is too tight can force a poor flexibility layout.
Agree it early
The size and position of the shaft are fixed by the architect and the structural designer, often before the gas design starts. Agreeing the riser needs at that stage avoids shaft changes after the structure is built.
Send us the shaft drawings for your tower and we will check that they work for the riser. See our PNG riser stress analysis service.