SIZE

• Soil type • i.e. minimum depth in cohesive = 750mm (not usually less than 1m in clay) • minimum depth in non‐cohesive = 450mm

2 storey building could have a foundation 500mm wide

• Other factors – • Presence of trees • Risk of frost • Proximity to adjacent services

The majority of soils in the UK have sufficient bearing capacity to have a simple strip of concrete.

2 storey building could have a foundation wider then 500mm special if soils isnt good

Most commonly used foundation for domestic construction in the last 60 years.

Cost

The WEAKER the soil and HEAVIER the building the WIDER the strip

Bearing Capacity of the soi

timing

Working space for labourer

Building load

Cheap

HEAVEY

• No additional working space required.

The most common form of foundation

Additional cost (more concrete) • Economical? • Service entry ducts • Good access for lorry

No need for planking and strutting (cost savings) • Potential time and labour savings

Easy to do

Designed by an engineer

for larger foundations

for sloping sites

• number of obstructions (e.g. old basements) in ground

foundations can be used for sloping sites, where access is restricted (i.e. for piling), there are obstructions in the ground.

where access for piling is difficult

– Always includes reinforcement

Spreads loads from ‘superstructure’ to piles

cheap and easy to load

Cast in situ or precast.

Need a lot of time

former mining; or • where the soil has significantly poor load bearing capacity • e.g. peat, filled ground, soft clay, soft silty clay and soft sandy clay

stiffened and reinforced concrete which extend under the entire footprint of the building

t foundations have to be individually engineered, and cover the entire footprint of the building to ‘float’ the load across the soil.

strip or pier foundations cover 50% of footprint

soils is of very poor bearing capacity

significant differential settlement likely

mining subsidence is possible

No standard solution – individually engineered (expensive) (unlike strip)

Cheap