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Foundation Repair Glossary: Terms Explained in Plain English

Last reviewed October 28, 2026 · 8 sources cited

Plain-English definitions of the terms in foundation inspection reports and repair quotes, written for homeowners, each linked to the guide that explains the idea in detail.

Terms

Underpinning
Adding support beneath an existing foundation, usually by extending new elements to deeper or more stable soil. The ASCE Texas Section guidelines note that underpinning generally does not improve areas of the foundation that were not underpinned.[1] See Piers and underpinning.
Settlement
Downward movement of a structure as the soil beneath it compresses or loses support. The InterNACHI inspector material notes settlement most often occurs early in a building's life and often slows to an equilibrium.[2]
Heave
Upward movement caused by soil swelling or freezing. See Expansive clay soil and Frost heave.
Differential movement or settlement
Different parts of a structure moving by different amounts. This is the pattern that cracks walls and racks doors, and the Colorado Geological Survey calls it the main source of structural damage in swelling and shrinking soils.[3]
Expansive soil
Soil, usually containing swelling clay minerals, that changes volume as its moisture changes. See Expansive clay soil.
Hydrostatic pressure
Pressure from water held in soil pushing against a wall or slab. The Oak Ridge National Laboratory foundation handbook says it can force water through walls, and that damp-proof coatings do not stop it.[4]
Footing
The widened base of a wall or column that spreads load onto soil.
Grade beam
A reinforced concrete beam at or near ground level spanning between deeper supports.
Push pier (resistance pier)
A steel pier pushed hydraulically into the ground against the weight of the structure. See Piers and underpinning.
Helical pier
A steel shaft with spiral plates that is screwed into the ground, with capacity depending on the plate size, shaft length and soil.[5]
Slabjacking (mudjacking)
Injecting grout or foam under a slab on ground to raise it or fill voids. The American Concrete Institute defines it that way and notes it does not correct underlying poor soil conditions.[6] See Slabjacking, mudjacking and foam.
Post-tensioned slab
A concrete slab reinforced with steel tendons that are tensioned after the concrete cures. The 2004 NRCS soil-hazards publication lists post-tensioned foundations among the precautions used on expansive soils.[7]
Pier and beam
A floor frame carried on beams that rest on piers, leaving a crawl space. See Pier and beam foundation repair.
Floor elevation survey
A set of floor height measurements used to map where a slab or floor has moved. The ASCE Texas Section guidelines caution that a single survey shows the shape at one moment and should not be the only basis for judging movement, because the original shape is usually unknown.[1]
Deflection ratio (L/360)
A way to express how far a floor or slab bends over a span. The ASCE Texas Section guidelines borrow L/360 from the residential code's live-load criterion as an analogous limit, so a 30-foot span (360 inches) would correspond to roughly one inch of deflection.[1]
Frost heave
Lifting caused by ice lenses forming in frost-susceptible, moist soil. See Frost heave.
Karst
Terrain formed on soluble rock such as limestone, where sinkholes can develop. See Sinkholes and karst.
Structural engineer (PE)
A licensed professional engineer who evaluates how a structure carries load. See Do you need a structural engineer?
Mechanic's lien
A claim a contractor, subcontractor or supplier can file against a property over unpaid work. The Federal Trade Commission advises getting lien releases or waivers before final payment.[8]
What Is a Foundation? Types, Parts and How It Can FailWhat a foundation does, the main types (slab, crawl space, basement, deep), and the terms you will hear.Foundation Repair Methods Compared: What Each One Does and Does Not DoPiers, slabjacking, crack repair, wall stabilization, drainage and pier-and-beam repair side by side.How to Read a Foundation Inspection ReportWhat observations, measurements and recommendations mean, and how to spot a report that is really a sales pitch.

Sources

Figures and claims marked with a number come from these sources. Dates are the publication or last-update dates shown by the publisher, where one was shown. Older sources are flagged in the text.

  1. Guidelines for the Evaluation and Repair of Residential Foundations, Version 1. Texas Section, American Society of Civil Engineers; adopted October 3, 2002, effective January 1, 2003.Written for Texas conditions and by its own terms not a standard of care. Widely used as a reference for slab and pier-and-beam evaluation. Published in 2002.
  2. Inspecting Foundation Walls and Piers. InterNACHI (International Association of Certified Home Inspectors), revised January 2013.Inspector-training material. It describes cracks by cause rather than by a fixed vertical/diagonal/horizontal chart.
  3. Home Construction on Shrinking and Swelling Soils (Special Publication 11). Colorado Geological Survey; Wesley G. Holtz and Stephen S. Hart, October 1978.Published in 1978. We use it for soil behavior and landscaping distances, not for costs or current practice.
  4. Foundation Design Handbook, Section 3.1: Drainage. Oak Ridge National Laboratory (U.S. Department of Energy); undated.
  5. Retrofitting a Foundation for Problem Soils. Journal of Light Construction; Nathaniel Eldon, builder; undated.A builder's account of one project, used here only to illustrate how helical piles are installed.
  6. RAP Bulletin 11: Slabjacking (ACI RAP-11). American Concrete Institute, Committee E706; primary author Fred R. Goodwin; copyright 2010.Covers slabs on ground (floors, pavements), not house foundations as a whole.
  7. Understanding Soil Risks and Hazards. USDA Natural Resources Conservation Service, National Soil Survey Center; ed. Gary B. Muckel, 2004.Older (2004). Its statistic on expansive soils is attributed in the document to the American Society of Civil Engineers.
  8. Hiring a Contractor. Federal Trade Commission, Consumer Information; March 2014.2014 publication. Cancellation-right and licensing rules vary by state.