SIZE

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.

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

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

2 storey building could have a foundation 500mm wide

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

Bearing Capacity of the soi

Cost

timing

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

Working space for labourer

Building load

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

• No additional working space required.

Cheap

The most common form of foundation

HEAVEY

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

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

Designed by an engineer

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

for larger foundations

for sloping sites

Easy to do

Spreads loads from ‘superstructure’ to piles

Cast in situ or precast.

cheap and easy to load

– Always includes reinforcement

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

Cheap

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

soils is of very poor bearing capacity

Need a lot of time

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

significant differential settlement likely

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

mining subsidence is possible

strip or pier foundations cover 50% of footprint