Building Construction Handbook, Eighth Edition

Typical procedure (for guidance only) †

5.0 m

5.0 m

1.0 m

2.5 m 2.5 m

2.9 m 2.9^ m

30 °

30 °

1 m wide strip

foundation

0.15 m x 0.5 m (assumed)

Note: For roof pitch >30°, snow load = 0„75 kN/m^2

Dead+imposed load is, 26„56 kN+7„80 kN = 34„36 kN

Given that the subsoil has a safe bearing capacity of 75 kN/m^2 ,

W = load...bearing capacity = 34„36...75 = 0„458 m or 458 mm

Therefore a foundation width of 500 mm is adequate.

Note: This example assumes the site is sheltered. If it is necessary

to make allowance for wind loading, reference should be made to

BS 6399-2: Code of practice for wind loads.

Dead load per m run (see pages 35 and 36)

Substructure brickwork, 1 m ¾ 1m¾ 476 kg/m^2 = 476 kg

.. .. .. .. cavity conc. (50 mm), 1 m ¾ 1m¾ 2300 kg/m^3 = 115 kg

Foundation concrete, 0„15 m ¾1m¾0„5 m ¾

2300 kg/m^3

= 173 kg

Superstructure brickwork, 5 m ¾ 1m¾ 221 kg/m^2 = 1105 kg

.. .. .. .. .. blockwork & ins., 5 m ¾ 1m¾ 79 kg/m^2 = 395 kg

.. .. .. .. .. 2 coat plasterwork, 5 m ¾1m¾22 kg/m^2 = 110 kg

Floor joists/boards/plstrbrd., 2„5 m ¾ 1m¾ 42„75 kg/m^2 = 107 kg

Ceiling joists/plstrbrd/ins., 2„5 m ¾ 1m¾ 19„87 kg/m^2 =50kg

Rafters, battens & felt, 2„9 m ¾ 1m¾12„10 kg/m^2 =35kg

Single lap tiling, 2„9 m ¾ 1m¾ 49 kg/m^2 = 142 kg

2708 kg

Note: kg ¾9„81 = Newtons

Therefore: 2708 kg ¾ 9„81 = 26565 N or 26„56 kN

Imposed load per m run (see BS 6399-1: Code of practice for dead

and imposed loads) †

Floor, 2„5 m ¾ 1m¾ 1„5 kN/m^2 = 3„75 kN

Roof, 2„9 m ¾ 1m¾ 1„5 kN/m^2 (snow) = 4„05 kN

7„80 kN

Foundations---Calculated Sizing