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Recommendations on calculation of slab thickness
≥ 3xDN
DN
d
d2
DN
d1
Minimum thickness of a steel-reinforced concrete slab with air ducts containing combustible components according to DIN 4120
Design features
Fire resistance class
One family house
F 0
Low-rise buildings
F 30-A
High-rise buildings
from 5 storeys
F 90-A
d1
d2
d1
d2
d1
d2
Min. depth for air duct installation* [mm]
50
50
50
Min. slab [mm]
50
50
50
Min. recommended thickness without taking into
account the crossing of wires through corrugated
pipes for electrical wiring [mm]
d = 180
d = 220
d = 240
d = 200
d = 240
d = 260
DN - Ø 63, 75 or 90 mm air duct
The data in the table also applies to installation in a monolithic slab.
*The data is only valid for the installation of a seamless screed on an insulated base (floating floor) with a minimum thickness of
25 mm.
