The allowable settlement is defined as the acceptable amount of settlement of the structure and it usually includes a factor of safety.
Allowable below shows the allowable foundation displacement into three categories: total settlement, tilting, and differential settlement.It indicates that those structures that are more flexible (such as simple steel frame buildings) or have more rigid foundations (such as mat foundations) can sustain larger values of total settlement and differential movement.
|Limiting factor||Maximum Settlement|
|Drainage||15 – 30 cm|
|Access||30 – 60 cm|
|1. Masonry walled structures||2.5 – 5 cm|
|2. Framed structures||5 – 10 cm|
|3. Chimneys, silos, mats||8 – 30 cm|
|Stability against overturning||Depends on H and L|
|Tilting of chimneys, towers||0.004L|
|Rolling of trucks etc.||0.01L|
|Stacking of goods||0.01L|
|Drainage of floors||0.01 – 0.02 L|
|High continuous brick walls||0.0005 – 0.001 L|
|One-storey brick mill building, wall cracking||0.001 – 0.002 L|
|Plaster cracking||0.001 L|
|Reinforced concrete building frame||0.0025 – 0.004 L|
|Reinforced concrete building curtain walls||0.003 L|
|Steel frame, continuous||0.002 L|
|Simple steel frame||0.005 L|
Where, L = distance between adjacent columns that settle to different amounts, or between two points that settle differently. Higher values are for regular settlements and more tolerant structures. Lower values are for irregular settlement and critical structures. H = Height and W = width of structure.