STRIP FOUNDATIONS

Traditional Strip Foundation

The simplest form of foundation is a mass-concrete strip positioned under free-standing walls or the walls of a building (see Fig 39). The minimum depth of ground cover for the foundation must be sufficient for the foundation not to be affected by ground movement or frost heave. This generally means excavating foundation trenches to a depth (‘D’) of 1000mm. Firmer sub-soils that are less susceptible to movement can have shallower foundation depths but this will depend on individual site conditions.

STRIP FOUNDATIONS

Fig. 40 Strip foundation with projection beneath and attached pier.

The thickness of the foundation (‘T’) must be a minimum of 150mm.

The width of the foundation (‘W’) depends on the bearing capacity of the soil and can be as little as the width of the wall (on rock sub-soils) or as much as 850mm. Typically, however, strip foundations are 650mm wide so as to provide working space in the trench.

Minimum width in mm for total load in kN/m of load-bearing wall of not more than 20kN/m; 30kN/m; 40kN/m; 50kN/m; eOkN/m; 70kN/m

Подпись: Physical characteristicsRock Not inferior Requires at least a pneumatic or other mechanically operated pick for excavation of wall In each case equal to width to sandstone, limestone or firm chalk

Gravel Compact Requires pick for excavation. Wooden peg, 50mm square, hard to drive in beyond 150mm 250; 300; 400; 500; 600; 650

Sand Compact Requires pick for excavation. Wooden peg, 50mm square, hard to drive in beyond 150mm 250; 300; 400; 500; 600; 650

Clay Stiff Cannot be moulded with fingers, requires pick/pneumatic/mechanical spade for removal 250; 300; 400; 500; 600; 650

STRIP FOUNDATIONS
Sandy Stiff Cannot be moulded with fingers, requires pick/pneumatic/mechanical spade for removal 250; 300; 400; 500; 600; 650