Page Summary

  • Heave means upward foundation movement caused by moisture added to unsaturated expansive clay in the active zone, where swelling pushes the slab and structure up.
  • Subsidence means downward foundation movement caused by moisture withdrawal from clay soils, where shrinkage reduces support and the structure drops.
  • Settlement means downward foundation movement caused by loads exceeding soil bearing capacity, including immediate distortion and longer term consolidation effects that can occur in many soil types.

Foundation movement gets described with one word far too often, settlement, even when the soil is actually swelling upward or shrinking from moisture loss. Diagnosing Heave Subsidence and Settlement definitions starts with precise terms, because the direction of movement and the mechanism behind it affect repair decisions, risk planning, and expectations over time. In Arizona, where soils and moisture conditions can change sharply with irrigation patterns, seasonal rainfall, and long dry stretches, accurate definitions help homeowners and commercial property managers talk about the same problem in the same language before any scope of work is discussed.

Which Way Is It Moving?

Guidelines for Diagnosing Heave, Subsidence and Settlement

Ron Kelm, P.E. | Nicole Wylie, P.E. | Forensic Engineers Inc. | Houston TX | www.forensicengineersinc.com

DEFINITIONS

The following definitions are taken from the Foundation Performance Association’s Document No. FPA-SC-13-0, Guidelines for the Evaluation of Foundation Movement for Residential and Other Low-Rise Buildings, published 15 Jul 07 at http://www.foundationperformance.org/:

Heave

Heave is the upward movement of an underlying supporting soil stratum, usually due to the addition of water to an unsaturated expansive soil in the active zone. When moisture is added to a soil with clay content, expansion occurs within the soil’s structure, and the corresponding area of the foundation and superstructure is moved upward. Heave normally only occurs within clayey soils that have a high suction potential and an available moisture source.

Subsidence

Subsidence is the downward movement of an underlying supporting soil stratum due to the withdrawal of moisture. When moisture is extracted from the soil, shrinkage occurs within the structure of the soil, and the corresponding area of the foundation and superstructure move downward. Subsidence normally occurs within clayey soils and is often the result of soil desiccation that is caused by trees or other large vegetation.

Settlement

Settlement is the downward movement of an underlying supporting soil stratum due to loading more than the bearing capacity of the soil below. When the vertical loads from above are in excess of the bearing capacity of the soil strata directly below the foundation, the foundation and superstructure move downward. Encompassed in settlement are a) the immediate elastic consolidation and distortion of granular or clay soil particles, b) slope instability, and c) the long-term consolidation resulting from gradual expulsion of pore water from voids between saturated clay soil particles. Settlement may occur in all types of soils.

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FAQs About Diagnosing Heave Subsidence and Settlement – Definitions

Heave is upward movement, most often linked to moisture gain in expansive clay within the active zone. Settlement is downward movement caused by soil deformation under load when the soil cannot support the applied pressure without compressing. The direction of movement and the moisture history usually separate the two.

Yes. A property can subside during long term drying and later heave if moisture conditions increase again, such as after vegetation removal, irrigation changes, drainage corrections, or plumbing leak events. The movement can also vary by area, with one corner rising while another drops.

No. Cracks can result from heave, subsidence, settlement, temperature and shrinkage effects in concrete, or framing movement. Crack pattern, location, and whether elevation measurements show highs versus lows are key to identifying the likely mechanism.

A reliable approach combines relative elevation measurements, symptom mapping, and site condition evaluation. Elevations can show whether the slab has a high area that suggests heave or a low area that suggests subsidence or settlement. History and moisture clues help confirm the direction.

Large trees can withdraw significant moisture from clay soils, causing shrinkage and downward movement near the root zone. Over time, this can create perimeter drop, especially in soils with swell shrink potential. Tree removal can later change the moisture balance again.

Yes. Leaks under the slab or near the foundation can add moisture to expansive soils and trigger localized swelling. That can lift the slab and create cracking and distortion that may look different from classic drying related subsidence.

Drainage that concentrates water near the foundation can increase moisture in expansive soils and contribute to heave. Poor water management can also create inconsistent wet and dry zones that lead to differential movement. Drainage that leaves soils consistently dry near the perimeter can contribute to subsidence in expansive clay.

Sometimes, but not always. One inspection captures conditions at a single point in time. If the movement is seasonal or ongoing, monitoring over time, combined with elevation rechecks and observation after weather changes, can provide clearer evidence of movement direction and stability.

Depending on the property, diagnosis can involve elevation surveys, soil sampling and classification, moisture evaluation, and hydrostatic plumbing leak testing when leaks are suspected. Additional assessments may be used based on foundation type and construction details.

A strong report typically includes the scope of evaluation, documents reviewed, observations and photos, an elevation plan, discussion of factors affecting soil moisture, testing results when performed, and clear conclusions with repair or monitoring recommendations that match the evidence.

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At Concrete Repairman LLC, we are proud to be a third generation foundation repair company with over 30 years of hands on experience. Led by James Belville, a master in concrete foundation repair, our team has served homeowners in Phoenix, Arizona, with unparalleled expertise and dedication. Floor grinding outcomes depend on the right tooling, a controlled approach, and understanding how the surface preparation affects the next finish system. Experience also matters when grinding intersects with broader slab performance concerns such as settlement, cracking, and edge movement.

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James Belville, a concrete and foundation repair expert, leads Concrete Repairman LLC. With over 30 years of experience, he provides top-quality repair solutions. Contact 602-418-2970 for expert foundation services.

A Legacy of Excellence in Foundation Repair

With over 30 years of hands-on experience, James Belville and the team at Concrete Repairman LLC have established themselves as trusted experts in foundation repair throughout the Phoenix Metro Area, serving communities like Ahwatukee, Mesa, Chandler, Scottsdale, and beyond. Our reputation for delivering high-quality repair solutions is rooted in our unwavering commitment to excellence, ensuring that every project is completed with the utmost precision and care.

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One of the common issues we encounter in Arizona foundations is efflorescence, a crystalline deposit caused by moisture intrusion. While it may appear harmless initially, efflorescence can be a warning sign of underlying problems such as cracks, stem wall deterioration, or basement moisture. Left unchecked, these issues can lead to significant structural damage. Our team specializes in diagnosing and repairing these moisture-related concerns, offering tailored solutions that prevent further damage and maintain your home’s long-term stability.

At Concrete Repairman LLC, call our Foundation Repair office in the Greater Phoenix Metro Area, including Gilbert, Glendale, Queen Creek, and Sun City. If you suspect foundation damage or want to protect your home from potential issues, contact us at  (602) 418-2970. Our expert team is ready to inspect thoroughly and offer the best repair solutions to safeguard your home for years.