The geology in and around Los Angeles and the highly desirable weather patterns are the most significant factors that cause foundation issues. We’ll explain each of these below and how they damage your structure.
Despite the coastal location near sandy beaches, Los Angeles is underlain predominantly by clay-rich soil. The dirt throughout most of Los Angeles County is at moderate to high risk of shrinking and swelling. The ground movement caused by expansive soil is hazardous for foundations for several reasons.
The expansive soil in Los Angeles grows in volume when it absorbs water, meaning that the ground around your home swells during rainfall or flooding.
The lateral and upward stress created by the increased hydrostatic pressure from the expanding soil can cause the concrete to crack. This damage is often severe and compromises the foundation’s structural integrity.
Clay-rich soil shrinks when it loses moisture, which typically occurs naturally when runoff or floodwaters evaporate in the California heat or drain deeper into the earth. Drying soil under and around your home’s foundation can shrink away from the concrete and leave it without the strength it needs to support your home’s weight.
The shrinking soil in LA is most problematic when it dries unevenly under your house. Some areas dry and pull away from the foundation more rapidly, causing differential settling of your structure.
Sections of the concrete that lose support can crack off of your house and sink further into the ground, leaving you with costly and hazardous structural cracks in your slab.
Finally, clay soil is highly absorbent and retains water for a longer time than a sandy or silty dirt would.
When runoff or floodwater are suspended in the ground, they get held against your porous concrete and can seep inside.
This is a particular problem in hilly areas of Los Angeles where structures are built into the sides of inclines, exposing more of your foundation to moisture in the soil. As such, water intrusion and moisture build-up are both issues throughout LA.
The sunny weather and minimal rainfall in Los Angeles may suit most residents, but it’s problematic for home foundations. The city receives just over 14 inches of rain annually, which is less than half of the national average.
LA also experiences extremely arid summers, averaging 0-2 inches of rain monthly, as well as excessively rainy winters. The wettest winter month brings nearly 400x the precipitation of the driest summer month.
The dry summers promote the shrinking of the soil and increase the risk of differential settling, while the heavier rainfall in the winter increases the ground’s volume and the likelihood of excess hydrostatic pressure on your foundation.
Additionally, the cycling between wet and dry soil throughout the seasons makes the effects of uneven settlement more significant and more prevalent.
California residents are well-acquainted with frequent and sometimes severe earthquakes. Los Angeles is situated near several fault zones, which cause regular earth-shaking. Most quakes in the area are minimal, but they have caused billions of dollars in property damage in the past decade alone.
Significant earthquakes can topple structures and shift the soil enough to create immediate structural damage. Small, routine shaking can damage plumbing lines that are commonly run through concrete slabs beneath your home, as well as water supply lines.
Seemingly insignificant underground leaks gradually weaken the soil under your home. The water flow can cause expansion of the earth and pressure on your slab, or differential settling, both increasing the risk of structural problems for residents in the area.
Lastly, much of Los Angeles is prone to flooding. The areas of low elevation near the coast are exposed to tidal flooding during winter rainstorms or from tsunamis caused by earthquakes off the coast.
The inland sections of LA can also experience flash flooding during heavy precipitation because the clay soil allows only slow drainage of runoff.
Flooding promotes excess hydrostatic pressure on your concrete foundation. It also increases the risk of water intrusion and moisture accumulation that can damage your foundation and the interior of your home.