Coastal Sands vs. Inland Clays: How Geography Dictates Foundation Failure

Key Points:

• Geographic Determinism: Your home’s foundation is fundamentally at the mercy of its underlying geology. Expansive inland clays act as slow-moving hydraulic presses, while coastal sands present severe risks of erosion, liquefaction, and washout [1, 2].
• The 30,000-Pound Threat: Inland expansive soils containing montmorillonite clay can swell up to 30% by volume when wet, exerting upward pressures of up to 30,000 pounds per square foot (psf)—more than enough force to snap concrete slabs and support beams [3, 4].
• Demographic Vulnerability: According to U.S. Census data, over 94.7 million Americans live in vulnerable coastline counties, a number that has grown significantly in recent decades, putting an unprecedented amount of real estate at risk of sand-related foundation failure [5].
• The Diagnostic Limit: Visual symptoms like drywall cracks and sticking doors are universal, but the underlying cure is hyper-local. Proper remediation requires analyzing the coefficient of linear extensibility (COLE) and local hydrostatic pressures [6, 7].
• Strict YMYL Disclaimer: The cost ranges and geographical data presented in this report represent algorithmic market estimates derived from aggregated historical, census, and USDA data. This report does not constitute official structural engineering diagnostics, legal advice, or financial guarantees. Only a licensed, local structural engineer can provide official engineering documents, loan-compliant safety diagnostics, and binding repair quotes.

For most homeowners, the discovery of a jagged, stair-step crack winding its way up a living room wall is a moment of profound anxiety. It is the sudden, terrifying realization that the largest financial investment of your life rests upon a dynamic, shifting, and unpredictable earth. We understand that anxiety. However, foundation failure is rarely a random event; it is governed by strict geotechnical science and geographical determinism. The soil beneath your home behaves according to its chemical composition, the local climate, and the immutable laws of physics.

This comprehensive report synthesizes United States Department of Agriculture (USDA) soil classifications, U.S. Census Bureau demographic data, and current geotechnical engineering research. By cross-referencing these datasets, we will explore why homes in coastal regions face entirely different structural threats than homes built on the sprawling, clay-heavy plains of the inland United States. Whether your property sits on shifting coastal sands or volatile inland clays, understanding the science beneath your slab is the first step toward reclaiming your peace of mind and protecting your home’s value.

Executive Summary (TL;DR)

For homeowners seeking an immediate understanding of their regional foundation risks, the following takeaways summarize the core scientific and economic realities:

• Inland Clays (Vertisols) Expand Violently: Found extensively in regions like Texas, Colorado, and the Mississippi River Valley, expansive clays can absorb massive amounts of water, swelling to exert up to 30,000 pounds of upward pressure per square foot [3, 8, 9]. This creates extreme seasonal “heaving” and “settling” cycles.
• Coastal Sands Suffer from Washout: Homes along the Atlantic, Pacific, and Gulf coasts face distinct challenges. Sandy soils lack cohesion. Under the stress of storm surges, shifting water tables, and erosion, coastal sands can liquefy or wash out entirely, leaving foundations suspended over voids [1, 10].
• Millions are Moving into High-Risk Zones: The U.S. Census Bureau recorded a 15.3% population growth in coastline counties between 2000 and 2017, placing 94.7 million Americans—and their homes—directly in the path of coastal erosion and sandy soil instability [5, 11].
• Geotechnical Solutions Vary by Geography: Coastal properties frequently require deep helical piers driven past unstable sands, while inland homes often require steel push piers, moisture barriers, or polyurethane foam injection to combat the violent expansion of clay [12, 13, 14].
• Market Estimates Range Widely: Based on projected 2026 data, minor crack repairs may cost as little as $300 to $1,000, while comprehensive piering systems for severe soil failure routinely range from $15,000 to over $30,000 depending on regional labor and soil complexity [15, 16, 17].

The Intersection of Geography, Demographics, and Soil Mechanics

To understand why foundations fail, we must first recognize that “soil” is not an inert, static material. Soil is an actively functioning, complex three-state ecosystem consisting of solid minerals, organic matter, a porous phase holding gases, and a liquid phase holding dissolved substances [18, 19]. In the context of residential construction, soil acts as the ultimate engineering medium upon which all structural loads are transferred [18].

When a home is built, the foundation’s load must not exceed the bearing capacity of the soil. Standard intact sedimentary rock might have a bearing capacity of 15,000 psf, while standard clays and silts may only safely bear 2,000 psf [20]. Problems arise when the environmental conditions surrounding the soil change—such as fluctuations in the water table, prolonged droughts, or severe storm events—altering the soil’s physical properties and compromising its ability to support the structure above.

Shifting Populations into Vulnerable Geographies

The vulnerability of residential foundations in the U.S. is heavily compounded by modern demographic shifts. Americans are increasingly migrating to regions characterized by challenging geotechnical conditions.

According to the U.S. Census Bureau, approximately 94.7 million people (representing about 29.1% of the total U.S. population) lived in coastline counties as of 2017 [5]. These coastal areas experienced a 15.3% population growth since the year 2000, creating a massive surge in housing development along the sandy, erosion-prone edges of the continent [5, 11]. The Gulf of Mexico region, in particular, was the fastest-growing coastline region, adding over 3 million people for a massive 26.1% demographic increase [5, 21].

Conversely, the inland regions—particularly the “Sunbelt” extending through Texas and the Front Range of Colorado—have also seen explosive residential development [3, 11]. These areas are dominated by entirely different soil profiles, most notably Vertisols and related expansive clays, which present their own terrifying structural hazards [8, 9].

Curious about the soil composition under your specific ZIP code? Use our local foundation calculator or access the service contact panel on this page to request a service quote from local contractors for an official site assessment.

Inland Clays: The Silent 30,000-Pound Threat

If you reside in Texas, Colorado, the lower Mississippi River Valley, or certain inland valleys of California, your primary foundation enemy is likely expansive clay [3, 9, 22]. The USDA classifies the most extreme of these soils as Vertisols.

The Science of Vertisols and Expansive Clays

Vertisols (from the Latin verto, meaning “to turn”) are clay-rich soils that undergo radical changes in volume corresponding to their moisture content [8, 23]. Globally, Vertisols occupy about 2.4% of the ice-free land area; within the United States, they cover approximately 2% of the total land mass, primarily concentrated in Texas and the Gulf Coast [8, 22].

The danger of Vertisols lies at a microscopic, chemical level. These soils contain a high percentage of specific, highly reactive clay minerals, most notably smectite and montmorillonite [3, 6, 24, 25]. The crystalline structure of these minerals consists of stacked tetrahedral and octahedral sheets. When water is introduced to the soil (via rainfall, snowmelt, or even a leaking plumbing pipe), water molecules are aggressively absorbed between these microscopic layers [24, 26].

This chemical attraction causes the clay particles to push apart. Think of it as millions of microscopic sponges rapidly inflating at the exact same time [3].

The Mechanics of Structural Destruction

When montmorillonite clay is exposed to water, the overall soil volume can expand by up to 20% to 30% [2, 3, 4, 22]. Because the soil is confined horizontally by the surrounding earth, the path of least resistance for this expansion is strictly vertical.

The resulting upward force is staggering. Geotechnical engineering studies demonstrate that fully saturated expansive clays can exert upward pressures of up to 30,000 pounds per square foot (psf) [2, 3, 4, 26, 27].

To put this into perspective, a standard residential concrete foundation slab is designed to distribute a downward load of only a few thousand pounds per square foot. When the soil below pushes upward with 30,000 psf of force, the concrete is easily overpowered. This phenomenon, known as “ground heave,” is more than enough to snap foundation slabs, break concrete stem walls, misalign doors, and rupture underground plumbing lines [4, 27].

Conversely, during prolonged summer droughts, the water trapped between the clay layers evaporates. The soil volume contracts just as violently as it expanded. The earth literally pulls away from the bottom of the home’s foundation, creating deep, wide polygonal cracks in the yard—sometimes extending over a meter deep—and leaving the heavy concrete slab entirely unsupported in mid-air [8, 22, 24]. Eventually, gravity wins, and the unsupported sections of the home sink downward, resulting in severe differential settlement [27, 28].

This cyclic, relentless “shrink-swell” behavior causes an estimated $7 billion in property damage annually in the United States, exceeding the combined financial damages caused by tornadoes, floods, earthquakes, and hurricanes [2, 6, 27, 28, 29].

The Coefficient of Linear Extensibility (COLE)

In the geotechnical and agronomic sciences, the severity of a soil’s shrink-swell capacity is quantified using a metric known as the Coefficient of Linear Extensibility (COLE) [6].

COLE measures the change in the linear dimension of an unconfined clod of soil as its moisture content is decreased from a moist to a dry state [7]. Homeowners and property buyers reviewing a USDA-NRCS (Natural Resources Conservation Service) soil survey for their lot should look for this specific metric [6, 24].

• Low Risk: COLE < 0.03
• Moderate Risk: COLE between 0.03 and 0.06
• High Risk: COLE > 0.06 [7]

A COLE value greater than 0.06 is generally considered the threshold for likely structural damage [6]. To visualize this: a COLE of 0.06 means that a 100-inch span of soil will physically expand by 6 inches when saturated with water [6, 24]. If one half of your home rests on a highly saturated section of soil (perhaps near a poorly draining downspout) while the other half rests on dry soil, the resulting differential movement will tear the structure apart.

Current building codes, such as Section R403.1.8 of the International Residential Code (IRC) and Section 1808.6 of the International Building Code (IBC), explicitly require specialized foundation designs when building on expansive soils [28].

Coastal Sands: Washout, Erosion, and Settlement

While inland homeowners battle the upward heave of clay, the 94.7 million Americans living in coastline counties face an entirely different geotechnical reality [5]. Homes built along the coastal perimeters of Florida, Rhode Island, the Carolinas, and California are frequently situated on sandy, loosely packed soils [10, 12].

The Mechanics of Sandy Soils

Unlike clays, sandy soils are gritty, highly porous, and possess very large particles with significant void spaces between them [30]. Because they lack the chemical binding properties (cohesion) of clay matrices, sandy soils do not expand when they get wet [30]. Instead, they drain rapidly.

While excellent drainage is generally a positive trait for preventing hydrostatic pressure build-up, the lack of cohesion makes coastal sands incredibly vulnerable to physical displacement. The primary threats to coastal foundations are erosion, washout, and liquefaction.

Hydrodynamic Washout and Erosion

Coastal sands are constantly subjected to dynamic water forces: tidal shifts, storm surges, and heavy spring rainfalls [10, 31]. As water rapidly moves through or across the loose sandy soil, it picks up and carries away the finer particles. Over time, the soil literally washes out from beneath the concrete footings of the home.

This process is exacerbated by:

1. Poor Drainage Engineering: Missing gutters or improper lot grading can funnel rainwater directly against the foundation, washing the sandy support out from under the slab.
2. Seawall Failure: Coastal properties often rely on bulkheads and seawalls. However, traditional sea walls suffer from erosion themselves. As the hydrodynamic forces pull sand out through the bottom or sides of the seawall, the sand beneath the wall liquefies, causing the heavy stones or concrete to collapse inward [1]. When the seawall fails, the foundation of the home quickly follows.
3. Storm Surges: High winds and sudden, massive flooding events can alter the topography of an entire coastal lot in a matter of hours, removing tons of load-bearing sand [10].

Globally, the erosion of coastal sand causes billions of dollars in damage annually through the loss of land and the disintegration of infrastructure [1]. Furthermore, global sand depletion from excessive dredging and sand mining has weakened natural coastal defenses (such as offshore sandbars and barrier islands), making coastal communities vastly more vulnerable to rising sea levels and violent storms [32].

Regional Market Estimates: The Cost of Foundation Failure

YMYL Disclaimer: The costs outlined below are algorithmic market estimates based on aggregated 2023, 2024, and projected 2026 industry data. These figures are strictly for educational and preliminary budgeting purposes. They do not constitute a binding quote or financial advice. Because individual soil complexity varies dramatically, ONLY a licensed structural engineer or certified foundation repair specialist evaluating your specific property can provide an accurate, official cost assessment.

When soil failure causes a foundation to crack, sink, or heave, intervention is required to transfer the weight of the home down to stable, load-bearing strata (such as deep bedrock) or to mechanically stabilize the existing soil.

Catching the signs of foundation failure early—such as sticking doors, stair-step brick cracks, or uneven floors—can save tens of thousands of dollars [16, 17, 29]. The longer a foundation is allowed to bend and settle, the more collateral damage is inflicted upon the roof, plumbing, and framing of the home.

The average national cost for generalized foundation repair sits between $4,500 and $5,100 [15, 16, 29]. However, this “average” encompasses everything from sealing a tiny non-structural crack to lifting a completely sunken house. True costs are dictated by the severity of the damage and the geographical remediation method required.

1. Minor Repairs and Preventative Maintenance

• Market Estimate: $300 to $1,500 [16, 17]
• Scope: Hairline crack sealing, epoxy/polyurethane crack injections (under 1/8 inch wide), minor grading adjustments, and basic drainage improvements [17].
• Context: While inexpensive, crack injection only treats the symptom. If the underlying clay is still expanding, or the coastal sand is still washing out, the crack will simply reopen or form elsewhere [16].

2. Slabjacking / Mudjacking

• Market Estimate: $500 to $1,500 per affected area [15, 16, 17, 29]
• Scope: Injecting a heavy cement/soil slurry (grout) under high pressure beneath a sunken concrete slab (driveways, walkways, garage floors) to lift it back to its original elevation [13, 29].
• Context: Mudjacking is a legacy technique that is highly budget-friendly [14, 29]. However, the slurry itself is very heavy. If the underlying soil is weak or saturated, the added weight of the mudjacking slurry can eventually cause the slab to sink again [14].

3. Polyurethane Foam Injection (Polyjacking)

• Market Estimate: $1,000 to $3,500 (or $800 to $2,500 per section) [15, 17]
• Scope: A modern alternative to mudjacking. High-density polyurethane foam is injected beneath the slab. The foam rapidly expands, filling voids and lifting the concrete [15, 17, 29].
• Context: This method is vastly superior for sandy coastal areas where washout has occurred. The foam is incredibly lightweight, preventing further burden on weak soils, and it is impervious to water, meaning it will not erode or wash out during the next storm [14].

4. Deep Foundation Piering (Underpinning)

When a home is suffering from severe differential settlement due to shrinking Vertisols or eroded sands, the structure must be permanently decoupled from the active topsoil. This is achieved via underpinning.

• Market Estimate (Per Pier): $1,000 to $3,000 per pier [15, 16, 17]
• Total Project Estimate: $15,000 to $30,000+ (an average home often requires 8 to 15 piers) [14, 17, 29]
• Helical Piers: Resembling giant steel screws, helical piers are rotated deep into the earth by hydraulic machinery until they reach a predetermined torque resistance [13, 14]. These are exceptionally well-suited for coastal sandy soils and loose loams where deep, reliable bearing capacity is required [13, 17].
• Steel Push Piers: Driven straight down into the earth using the sheer weight of the house as resistance, push piers are driven until they strike bedrock or absolute refusal [14]. These are heavily utilized in inland clay regions (like Texas and Colorado) to bypass the upper active zone of expanding clays and anchor the home directly to unmoving stone [4, 14, 29].

5. Comprehensive Replacement and Mitigation

• Market Estimate: $15,000 to $100,000+ [17, 29, 33]
• Scope: In extreme cases where 30,000 psf clay heave has shattered the foundation beyond repair, partial or total replacement is required. This often involves excavating the problematic soil entirely, replacing it with non-expansive engineered fill, installing elaborate sub-surface drainage, and pouring a new slab utilizing structural “void forms” (cardboard boxes placed under the concrete that leave an empty space for the clay to expand into without touching the slab) [3, 4, 17].

Are you seeing stair-step cracks in your brickwork or noticing bouncy floors? Don’t delay. Use our market assessment tool to generate an algorithmic cost estimate, or utilize the contact panel to connect directly with a licensed structural engineer.

Diagnostic Protocols and Modern Geotechnical Engineering

Because a homeowner cannot look at a patch of dirt and intuitively deduce its COLE value or its underlying hydrostatic pressure, professional diagnostic protocols are mandatory.

When significant foundation movement is suspected, the standard procedure begins with a Geotechnical Soil Report. A licensed soil scientist or geotechnical engineer will bore holes deep into the lot, extracting core samples. These samples are analyzed in a laboratory to determine the exact percentage of smectite/montmorillonite clay, the soil’s load-bearing capacity, its permeability, and the depth of the active moisture zone [4, 6, 28].

The cost of these independent geotechnical reports generally ranges from $500 to $3,500 depending on the complexity of the site and the depth of the borings [15, 16]. While this may seem like an expensive preliminary step, skipping it is architectural malpractice. Attempting to install concrete piers into expansive clay without knowing the depth of the bedrock, for example, can result in “bedrock heave”—a catastrophic scenario where the expanding clay forces the bedrock itself upward, snapping the newly installed piers and destroying the home [4].

Similarly, for coastal communities, emerging innovations like electrically cemented sand are being tested to combat erosion [1]. By applying a mild electrical current to coastal sand, naturally occurring dissolved minerals in the seawater crystallize between the sand grains, gluing them together into a rock-like mass. Costing only $4 to $8 per cubic yard (compared to $70 for traditional chemical grouting), this technology may soon revolutionize how we stabilize coastal foundations [1].

Understanding the geographic reality of your soil is paramount. Coastal sands and inland clays operate under completely different laws of physics, requiring entirely different engineering solutions. By recognizing the specific geographical threats native to your region, you can transition from an anxious observer of drywall cracks into an empowered, informed homeowner.

Frequently Asked Questions

How do I know if my home is built on expansive clay or Vertisols? The most definitive way to know is by consulting the USDA Web Soil Survey, which maps soil orders across the country, or by hiring a geotechnical engineer to test your soil’s COLE (Coefficient of Linear Extensibility) [6, 26, 28]. Visually, expansive clays often reveal themselves during extreme dry spells by forming massive, deep polygonal cracks in the yard (sometimes an inch or more wide) as the soil shrinks and pulls away from your foundation [8, 24, 27]. If your region alternates between severe droughts and heavy rains (like Texas or Colorado), you are at high risk.

Are foundation repairs caused by soil movement covered by standard homeowner’s insurance? Generally, no. Standard homeowner’s insurance policies typically exclude coverage for damage caused by “earth movement,” which includes gradual settling, shrinking, and expanding soils (heave) [10, 27]. Insurance may cover foundation damage if it was caused by a sudden, covered peril (like a burst indoor plumbing pipe that washed out the soil), but natural geological shifts and poor regional soil conditions are considered maintenance issues [10].

Why are helical piers recommended for sandy coastal areas instead of traditional concrete piers? Coastal sands lack cohesion, making traditional concrete poured piers vulnerable to erosion, high water tables, and saltwater degradation over time [14]. Helical piers are made of galvanized steel and feature large, screw-like plates. They can be rotated deeply into the earth with minimal excavation, biting into denser, load-bearing soil strata far below the unstable, shifting surface sands [13, 14].

What is the difference between mudjacking and polyurethane foam injection? Both are “slabjacking” techniques used to lift sunken concrete. Mudjacking uses a heavy mixture of water, soil, and cement. While cost-effective, its heavy weight can further compress weak soils [14, 29]. Polyurethane injection (polyjacking) uses a two-part, high-density chemical foam that expands violently to lift the slab. The foam is incredibly lightweight, cures in minutes, and is waterproof—making it ideal for coastal areas where preventing future soil washout is critical [14, 15, 29].

What does it mean when building codes mention a “COLE value greater than 0.06”? COLE stands for Coefficient of Linear Extensibility, a laboratory measurement of how much a specific soil sample shrinks and swells as its moisture content changes [6]. A COLE value of 0.06 means that a 100-inch section of dry soil will expand by 6 inches when saturated with water [6, 24]. Because this level of expansion can exert massive upward force (up to 30,000 psf) capable of breaking concrete, building codes require specialized engineering for any lot testing above this threshold [7, 28].

Citations and Sources

1. Wikipedia contributors, “Soil,” Wikipedia, The Free Encyclopedia. https://en.wikipedia.org/wiki/Soil
2. ISRIC, “What is soil?” https://isric.org/all-about-soil/
3. NOAA, “Learn About Soil Types,” https://www.nesdis.noaa.gov/about/k-12-education/understanding-our-planet/learn-about-soil-types
4. Department of Energy, “DOE Explains…Soil,” https://www.energy.gov/science/doe-explainssoil
5. USDA NRCS, “What is Soil Health?” https://www.nrcs.usda.gov/conservation-basics/natural-resource-concerns/soil/soil-health
6. University of Idaho CALS, “Vertisols,” https://www.uidaho.edu/agricultural-life-sciences/soil-orders/vertisols
7. USDA NRCS, “Vertisols,” https://www.nrcs.usda.gov/conservation-basics/natural-resource-concerns/soil/vertisols
8. Rockhouse Construction, “Why Rhode Island Homes Are Prone to Foundation Problems,” https://www.rockhouseconstruction.com/foundation-repair-warning-signs-for-rhode-island-homeowners
9. Medium (Environmental Defense Initiative), “The world is running out of sand,” https://medium.com/@environmentaldefenseinitiative/the-world-is-running-out-of-sand-85abf2a79ca9
10. Chesapeake Quarterly, “The Sand Deficit,” http://www.chesapeakequarterly.net/sealevel/main15/
11. Earth.com, “Fighting coastal erosion with a shockingly simple solution,” https://www.earth.com/news/fighting-coastal-erosion-with-a-shockingly-simple-solution-and-it-actually-works/
12. Maine DEP, “Coastal Sand Dune Systems,” https://www.maine.gov/dep/land/nrpa/dunes/faq-sand-dune-storm-repai.pdf
13. PowerLift Foundation Repair, “Foundation Repair Cost Guide: What to Expect in 2026,” https://www.powerliftfoundationrepair.com/2026/02/13/foundation-repair-cost-guide-what-to-expect-in-2026/
14. Douglas Foundation Repair, “Cost of Foundation Repair in 2023,” https://www.douglasfoundationrepair.com/blog/6-20-23-cost-of-foundation-repair-in-2023.html
15. Lift Texas Construction, “Comprehensive Cost Guide to Foundation Repair in Texas,” https://lift-texas.net/comprehensive-cost-guide-to-foundation-repair-in-texas/
16. Sweeten, “Foundation Repair Costs by Severity of Damage,” https://sweeten.com/blog/home-renovation-cost-guides/foundation-repair-damage-type/
17. Golden Bay Foundation Builders, “The Cost of Foundation Repairs in the Bay Area,” https://goldenbayfoundationbuilders.com/the-cost-of-foundation-repairs-budgeting-for-bay-area-homeowners/
18. Fauquier County Government, “Land Development Issues Identified By Soil Maps,” https://www.fauquiercounty.gov/government/departments-a-g/community-development/land-development/soils/land-development-issues-identified-by-soil-maps
19. Wikipedia contributors, “Shrink–swell capacity,” Wikipedia, The Free Encyclopedia. https://en.wikipedia.org/wiki/Shrink%E2%80%93swell_capacity
20. Texas Department of Licensing and Regulation, “Foundations on Expansive Soils,” https://www.tdlr.texas.gov/ihb/pdf/TB1001.pdf
21. Purdue University Extension, “Expansive Soils,” https://www.extension.purdue.edu/extmedia/rw/rw-3-w.pdf
22. U.S. Census Bureau, “Millions of Americans Live in Coastline Regions,” https://www.census.gov/library/stories/2019/07/millions-of-americans-live-coastline-regions.html
23. U.S. Census Bureau, “Coastal Areas and Preparedness,” https://www.census.gov/topics/preparedness/about/coastal-areas.html
24. National Ocean Economics Program, “Demographics: Population and Housing Definitions,” https://oceaneconomics.org/cstecon_pop_housing/cecon_pop_housing.html
25. U.S. Census Bureau, “About Emergency Management: Coastal Areas,” https://www.census.gov/topics/preparedness/about.html
26. U.S. Census Bureau, “Coastline America Infographic,” https://www.census.gov/content/dam/Census/library/visualizations/2019/demo/coastline-america.pdf
27. Rutgers University Marine Data Lab, “Coastal Population Report,” https://datalab.marine.rutgers.edu/2013/03/coastal-population-report/
28. California Soil Resource Lab, “Linear Extensibility Percent,” https://casoilresource.lawr.ucdavis.edu/gmap/help/defn-linear-extensibility.html
29. Insurance Information Institute, “Spotlight on Catastrophes: Insurance Issues,” https://www.iii.org/article/spotlight-on-catastrophes-insurance-issues
30. Colorado Geological Survey, “Expansive Soil and Rock,” https://coloradogeologicalsurvey.org/hazards/expansive-soil-rock/
31. Virginia Department of Energy, “Expansive Soils,” https://www.energy.virginia.gov/geology/ExpansiveSoils.shtml
32. Level Up Concrete Repair, “Expansive Soil Damage in Colorado,” https://levelupmyconcrete.com/concrete-leveling/expansive-soil-damage-colorado/
33. Barton Supply, “Concrete Void Forms: Dealing With Colorado’s Expansive Soils,” https://www.barton-supply.com/the-latest/blog/posts/2019/february/concrete-void-forms-one-way-to-deal-with-colorados-expansive-soils/
34. Concrete Foundations Association, “Soils & Excavation Safety,” https://cfaconcretepros.org/resources/TN-011-Soils-and-Excavation.pdf
35. The Foundation Works, “How Much Does House Foundation Repair Cost?” https://www.thefoundationworks.com/how-much-does-house-foundation-repair-cost/
36. Solid Foundations, “How Much Does Foundation Repair Cost in Florida?” https://solidfoundations.com/how-much-does-foundation-repair-cost-in-florida/
37. Foundation Solutions Group, “Ultimate Guide to Foundation Repair,” https://www.foundationsolutionsgroup.com/ultimate-guide-to-foundation-repair/
38. The Home Depot, “7 Ways to Repair Foundations,” https://www.homedepot.com/c/ah/7-ways-to-repair-foundations/9ba683603be9fa5395fab9017e00a38a
39. Study Guides, “Vertisols Overview,” https://studyguides.com/study-methods/overview/cmmn8i85lgetk01aa3ugz26wc
40. Soils4Teachers, “Soil Profiles,” https://www.soils4teachers.org/profiles
41. USDA NRCS, “The Twelve Soil Orders,” https://www.nrcs.usda.gov/sites/default/files/2022-06/orders_hi.pdf
42. Grokipedia, “Vertisol,” https://grokipedia.com/page/Vertisol