The ground
is not still.
Every cracked slab, leaning wall and sinking floor has a geologic address. FRN maps the soils, rock, water and storms that move buildings, region by region and event by event, with the engineering research behind it.
Foundation failure is regional.
A slab in Houston fails for a different reason than a slab in Tampa, Denver or Tucson. The soil, the rock below it and the water moving through it decide how a building moves and what a real repair has to reach. Start with the ground you live on.
Florida Karst
Limestone dissolving under sand and clay. Sinkholes, raveling and cover collapse.
Explore →Texas & Gulf Coast Clays
Expansive clays that swell when wet and shrink in drought, lifting and dropping slabs.
Explore →Front Range Bentonite
Some of the most aggressive swelling soils in North America, along the Rockies.
In developmentArizona & Desert Southwest
Collapsible soils, caliche and earth fissures. Dry ground that holds until water reaches it.
Explore →Pacific Coast
Saturated sands and bay fill that lose strength when the ground shakes.
In developmentPacific Northwest
Steep slopes, heavy rain and glacial deposits. Landslides and creep.
In developmentMidwest Frost & Loess
Frost heave, wind blown silt and basement walls pushed in by saturated soil.
In developmentThe World
Mexico City, Jakarta, Venice, Pisa, Christchurch. Cities built on ground that moves.
In developmentFlorida. Texas. Arizona.
Three of the most active foundation states in the country, and three completely different reasons buildings move. The repair that works on one ground can fail on the next, which is why the diagnosis has to start with the geology.
Most of the state sits on limestone that groundwater slowly dissolves. Sand and clay cover the rock, the water table is shallow, and the coasts are built on dredged fill. Voids open below long before anything shows at the surface.
- The ground
- Sand and clay over karst limestone
- What moves it
- Sinkholes, raveling soil, high water, storm surge
- What a repair must reach
- Competent bearing below the weak and raveled zone
Texas is one of the busiest foundation repair markets in the United States, and the reason is in the soil. Expansive clays under Houston, Dallas, Fort Worth, Austin and San Antonio swell when they take on water and shrink hard in drought, lifting and dropping slabs season after season.
- The ground
- High plasticity expansive clay
- What moves it
- Wet and dry cycles, drought, trees, leaking lines
- What a repair must reach
- Below the active moisture zone of the clay
Desert soils can stand firm for decades and then collapse the first time water reaches them, from irrigation, roof runoff or a broken line. Caliche and clay pockets add to it. Groundwater pumping has also lowered whole basins: the Arizona Geological Survey has mapped about 169 miles of earth fissures, and land near Eloy dropped 15.4 feet between 1952 and 1985.
- The ground
- Collapsible desert soil, caliche, clay pockets
- What moves it
- Wetting collapse, basin subsidence, earth fissures
- What a repair must reach
- Stable soil below the zone water can reach
How ground moves a building.
Cracks are symptoms. The cause is almost always one of a handful of physical processes in the soil and rock. Name the process and the right repair usually becomes obvious.
Settlement
Soil compresses under load. Uneven settlement, not total settlement, is what cracks walls.
Heave
Expansive clay takes on water and swells, pushing slabs and footings upward.
Liquefaction
Shaking drives up pore water pressure in loose saturated sand until it behaves like a fluid.
Karst Collapse
Acidic groundwater dissolves limestone. The soil above ravels into the void until the surface gives.
Scour & Surge
Storm water strips soil from beneath slabs, piles and seawalls faster than any other force.
Subsidence
Pumping groundwater or draining organic soil lowers the land itself, sometimes across whole cities.
What catastrophe teaches.
Disasters are the largest foundation tests ever run. Each one left a lesson that changed how engineers investigate and repair the ground.
A sinkhole roughly an acre across opened in May, taking a house, a swimming pool and part of a car dealership. It filled with water and is now a lake.
Florida’s limestone can hold a void for years before the cover above it fails. Surface fixes do nothing about what is happening below.
The magnitude 6.9 Loma Prieta earthquake hit the Marina District hardest, a neighborhood built largely on fill placed in the bay.
Two buildings on the same street can perform completely differently. What lies beneath matters more than distance from the fault.
After more than a decade closed, the Leaning Tower reopened. Engineers had reduced its lean by carefully removing soil from beneath the high side.
The most famous foundation failure in the world was fixed by understanding the soil, not by fighting the structure.
The February earthquake triggered widespread liquefaction in the eastern suburbs. Whole neighborhoods were later abandoned.
Some ground cannot be economically repaired. Knowing that before you build is the cheapest engineering there is.
A sinkhole opened beneath a bedroom at night and a man was lost. The house was demolished and the hole filled.
Cover collapse sinkholes give little warning. Investigation, not appearance, is what separates a sound lot from a dangerous one.
Hurricane Ian’s storm surge swept across the island, leaving many shallow homes as bare slabs while elevated structures on deep foundations stood.
On the coast, scour is a foundation design load. Depth of support decides what is still standing after the water leaves.
Built on primary sources.
FRN draws on government survey data, post disaster investigations and university engineering research. When we make a claim, we tell you where it came from.
Tell us what the ground is doing.
Send the basics and we will point you toward what to check, what to ask and who should look at it. Florida questions go to the network’s engineering and waterproofing teams.
- 01Property city and state
- 02What you are seeing: cracks, sloping floors, sticking doors, water, a depression in the yard
- 03How long it has been happening and whether it is getting worse
- 04Any inspection report, soil boring or contractor proposal you already have
When the science is your problem.
FRN is informational. When the ground under your Florida property is moving or water is getting in, these are the network’s engineering and waterproofing resources.
Foundation Masters
Civil forensic engineering, foundation stabilization, push piers, driven piles and sinkhole repair across Florida. Florida Certificate of Authorization CA# 30969.
Visit foundationmasters.com →Foundation Waterproofing 101
Foundation waterproofing, collection lines, sump systems and water intrusion correction for Florida homes and buildings. CGC 1539326.
Visit foundationwaterproofing101.com →The Foundation Repair Network publishes general educational information about geology, soils and foundation performance. It is not an engineering evaluation of any specific property. Conditions vary site by site; consult a qualified engineer before making repair decisions.