Construction Practices & Soil Conditions That Lead to Settling Slab Foundations
The following paragraphs offer some additional information for some of the more common reasons for slab settlement:
Drying and Shrinking of Soil Under the Slab
Poorly Compacted Fill Soils
When the structure is built, footings may be deep enough to extend below the fill soils, but the slab may remain on the fill.
Over time, loosely compacted fill soils will consolidate beneath the weight of the slab or fill layers above, causing a void to form below the slab. When this happens, the slab will begin to crack and break as it settles into the void.
Soil Washout - Plumbing Leaks
This displaced soil creates a void beneath the slab, causing the slab to crack and settle.