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Urban Redevelopment Authority (URA)

Service Ducts

Find out the GFA treatment for service ducts

Last updated 6 June 2026

Service ducts, including the thickness of the walls, are included as GFA once at the lowest floor, if the vertical shaft is entirely a void space.

If the service ducts are slabbed over at every floor, the service duct at each floor is included as GFA. Non-load bearing fire-stop material to compartmentalise the service ducts are excluded from GFA.

Section diagram showing service duct GFA counted at the lowest storey

Service Duct