Building Construction Handbook, Eighth Edition

Guidance † simply supported slabs are capable of the following

loading relative to their thickness:

Note: As a rule of thumb, it is easy to remember that for general

use (as above), thickness of slab equates to 1/24 span.

*Imposed loading varies with application from 1„5 kN/m^2 (153 kg/m^2 )

for domestic buildings, to over 10 kN/m^2 (1020 kg/m^2 ) for heavy

industrial storage areas. 500 kg/m^2 is typical for office filing and

storage space. See BS 6399-1: Loading for buildings. Code of

practice for dead and imposed loads.

For larger spans † thickness can be increased proportionally to the

span, eg. 6 m span will require a 250 mm thickness.

For greater loading † slab thickness is increased proportionally to

the square root of the load, eg. for a total load of 1500 kg/m^2

over a 3 m span:

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 1500

800

r

¾125 = 171„2 i:e:175 mm

Continuous beams and slabs have several supports, therefore they

are stronger than simple beams and slabs. The spans given in the

above table may be increased by 20% for interior spans and 10%

for end spans.

Deflection limit on reinforced concrete beams and slabs is 1/250 span.

Refs. BS 8110-1: Structural use of concrete. Code of practice for design

and construction.

BS EN 1992-1-1: Design of concrete structures. General rules and

rules for buildings.

See page 546 for deflection formulae.

Thickness

(mm)

Self

weight

(kg/m^2 )

Imposed

load*

(kg/m^2 )

Total load

(kg/m^2 ) (kN/m^2 )

Span

(m)

100 240 500 740 7„26 2„4

125 300 500 800 7„85 3„0

150 360 500 860 8„44 3„6

Simple Reinforced Concrete Beam and Slab Design (2)