Frost Heave: How Freezing Soil Lifts a Foundation

Quick answer

Frost heave is the upward movement of the ground caused by ice lenses that grow in freezing soil when water is drawn toward the frozen layer, lifting whatever rests on it, including slabs, porches and footings placed too shallow.

It needs three things together: freezing temperatures, a water supply, and soil that lets water move. Take away any one and the heave stops, which is why drainage and frost-depth footings are the standard defenses.

Quick facts

The key facts about Frost Heave, with sources:

Three conditions: Freezing temperature, a source of water, and soil that lets water reach the freezing front ²
What lifts the ground: Ice lenses that grow as water is drawn to the frozen layer ²³
Most susceptible soils: Silty soils and highly structured clay soils with a high winter water table ³
Least susceptible soils: Well drained, very gravelly or very sandy soils ³
Code defense: Footings below the frost line, frost-protected shallow foundations, ASCE 32, or solid rock ⁴
Also after the freeze: Thawing ice lenses raise soil water content and cut soil strength ²³
Frost depth: Set locally. The model code points to a frost line in a jurisdiction table ⁴

Key takeaways

Frost heave needs freezing temperatures, water and a soil that moves water. Removing one of the three stops it.
The ground rises because ice lenses grow, not just because water expands as it freezes.
Silty and highly structured clay soils with a high winter water table are the most susceptible, per NRCS. Clean gravel and sand are the least.
Footings are protected by going below the frost line, by approved frost-protected shallow designs, or by sitting on rock. Porches, decks and slabs on grade are the usual victims when they are not.
Uneven heave and thaw can crack and tilt a structure. A record of movement through the seasons helps an engineer read it.

What frost heave is

When ground freezes, you might expect the water in it to push the soil up simply by turning to ice. That is only part of the story.

In frost-susceptible soil, ice grows in thin layers called ice lenses, and each lens pulls more water up from the unfrozen soil below.

The lens thickens, the ground above rises, and anything resting on it rises too.

General information, not a diagnosis of your house.

University of Minnesota researchers state the conditions simply: there must be freezing temperatures in the soil, there must be a water source to feed ice lens growth, and the soil must allow enough water to move to the freezing front within the time the freeze advances ².

NRCS defines potential for frost action as the likelihood of upward or lateral expansion of soil caused by segregated ice lenses, and of the collapse and loss of strength when the soil thaws. It says damage from frost heave and low strength during thaw affects pavements and other rigid structures ³.

Frost heave is one of several ways ground can move a foundation. See foundation heave for the general idea of upward movement, and expansive clay soil for the moisture-driven kind that has nothing to do with freezing.

Frost heave vs. expansive clay heave

Frost heave comes from ice lenses in cold weather and is mostly gone when the ground thaws. Expansive clay heave comes from clay minerals taking up water and can happen at any temperature. A house in a cold, clay-rich area can have both.

How frost heave happens, step by step

The mechanism is still studied by researchers, but the sequence below matches the Minnesota report and the NRCS definition:

Cold reaches the soil: The air stays below freezing long enough that the freezing front moves down into the ground ².
Water is available: A high water table, saturated soil or runoff keeps unfrozen water within reach ²³.
Ice lenses form: In soil with small particles, growing ice excludes the particles and water keeps flowing to the lens, so ice layers thicken ².
The ground rises: The thickening lenses lift the soil and any slab, post or footing in the frozen zone.
Uneven lifting occurs: Minnesota researchers note that volume change is usually uneven, causing differential movement and structural damage ².
Thaw weakens the soil: In spring the lenses melt, water content rises and soil strength drops ²³.

Diagram Soil rising under a structure, compared with soil sinking

Illustrative drawing contrasting soil that moves up with soil that moves down. It is not to scale and not a design for any house.

Which soils are prone to frost heave

Susceptibility classes follow the NRCS Technical Guide. NRCS assumes soil not insulated by vegetation or snow and not artificially drained.
Soil condition	Frost susceptibility	Why
Silty soils with a high winter water table	Most susceptible	Small particles let water move to the freezing front ³
Highly structured clay soils with a high winter water table	Most susceptible	Water supply and soil structure feed ice lenses ³
Well drained soils	Least susceptible	Little water reaches the freezing zone ³
Very gravelly or very sandy soils	Least susceptible	Water does not move up easily to a freezing front ³
Any soil, once drained or replaced	Reduced risk	Lowering the water table or removing frost-susceptible soil are used defenses ²

Soil type alone does not prove a problem

NRCS rates map units. A silty lot with good drainage and footings below frost depth may never heave. Site-specific testing and a local engineer give a better answer than a survey rating.

Example: which of four porches is most at risk

An example only. Four invented porches, each judged by the three conditions the Minnesota report lists ². None describes a real property.

Porch	Freezing winter?	Water supply?	Soil lets water move?	Heave risk
A	Yes	High water table	Silty	Highest; all three conditions are present
B	Yes	Well drained slope	Silty	Lower; water supply is limited ³
C	Yes	Wet, flat lot	Clean gravel	Lower; coarse soil does not move water up ³
D	No freezing	High water table	Silty	No frost heave; other movement can still occur

Removing any one condition protects the structure. That is why local practice combines frost-depth footings, drainage and sometimes replacement of frost-susceptible soil.

Where frost heave shows up on a house and yard

The most common victims sit on shallow supports. FEMA describes shallow foundations as those supported by soils relatively close to the surface of the surrounding grade ¹, so they sit nearest the freezing zone.

A porch, step, or deck post set only a short way into the ground can rise in winter and drop back in spring. A garage slab or a walkway slab on grade can lift at its edge.

Footings are the other place to look. The code requires footings to be protected from frost, and Minnesota researchers describe a long list of defenses: lowering the water table, removing frost-susceptible soil under the foundation, and using impervious membranes, chemical additives and foam insulation ⁴².

Penn State engineers add that footings should be placed below the frost line, and that soil should be protected from freezing before and after concrete is placed in cold weather ⁵.

A heated house on a proper footing is generally protected, but unheated additions, porches and garages attached to it may not be. Where a porch and the main house sit at different depths, they can move by different amounts, and the joint between them can open and close with the seasons.

Defenses against frost heave, and what each one cannot do

What the defenses give

Footings below the frost line keep the bearing level out of the freezing zone ⁴.
Frost-protected shallow foundations let insulation keep frost away from a heated building without deep footings ⁴.
Drainage and a lower water table cut the water supply that feeds ice lenses ².
Replacing frost-susceptible soil removes the soil part of the three conditions ².

Where they fall short

The frost line is a local number from a jurisdiction table, so a design copied from another region can be wrong ⁴.
Frost-protected shallow designs are limited to buildings kept warm. The code says they shall not be used for unheated spaces such as porches, utility rooms, garages and carports ⁴.
Drainage depends on outlets staying clear and on local rules for discharge.
Soil replacement is major excavation work that belongs to professionals.

What we cannot tell from frost alone

A winter lift does not mean a house is failing. Movement can be seasonal and recover on thaw. What matters is whether the structure moves back, whether cracks keep growing, and whether other causes are involved. A crack pattern is a clue, never a diagnosis.

Soil behavior depends on mineralogy, moisture, stress and drainage. One soil type is not proof of a problem. Susceptibility classes are screening tools, and the Minnesota researchers note that the frost heave process is not fully understood ².

Frost depth varies by place, by winter, and by snow cover. The model code points to a frost line in a table the local jurisdiction fills in ⁴. We do not print depths, because a number from another region can mislead.

What drives the cost of frost-related work

We print no prices, because fair numbers need dated local quotes. The cost drivers are the footing depth required by local frost depth, the soil to be excavated or replaced, drainage work and outlets, insulation if a frost-protected design is used, access and local permit requirements.

For an existing porch or slab that has heaved, drivers include whether it can be re-supported, replaced or left alone, and whether the main foundation is involved. See the foundation cost guide and the cost calculator for how quotes are assembled.

How a professional evaluates frost heave on a house

A general sequence. The engineer sets the actual scope.

Collect history: Which parts move, when, and whether movement recovers on thaw.
Check the supports: Footing depth, pier details and whether the structure is heated or not.
Check the water: Grade, downspouts, drains and any high groundwater near the structure.
Review the soil: Soil survey data and, if needed, borings to see whether the soil is frost-susceptible.
Measure movement over time: Dated readings through at least one freeze and thaw cycle show what is seasonal.
Recommend a response: Drainage, re-support or replacement, designed for loads and site.

Never dig beside a footing to “check” frost depth

Digging next to a foundation can undermine it, and trenches can collapse. Frost depth for your area comes from your building department or a local engineer, not from exploratory digging.

What a homeowner can safely do before and after winter

Clear gutters in fall and keep downspouts discharging away from the house, so less water reaches the soil near the foundation.
Keep the ground sloping away from the walls. The model code asks for lots graded to drain surface water away from foundation walls ⁴.
Watch for ponding next to steps, porches and slab edges before the ground freezes.
Note and photograph any lifted edges, gaps or tilts in winter, with the date and the weather.
Compare the same spots after the thaw to see whether the movement recovered.
Do not force a stuck door or window while the ground is frozen. Wait for thaw and note whether it recovers.

See the drainage and grading guide for more on water at the wall, and the elevation log for tracking movement.

Warning signs and when to call a structural engineer

Seasonal lifting that returns to normal is different from movement that stays. Call a licensed structural or geotechnical engineer when you see:

Cracks that widen, lengthen or fail to close after the thaw.
A porch, stoop or addition that separates from the house and does not return.
A wall that bows, leans or shows a horizontal crack.
Doors and windows that stick along with new cracks.
A slab edge that has stepped up and stayed up.
Any safety doubt.

A pattern is a clue, not a diagnosis. The structural engineer guide explains who to call first.

What the model code says about frost

IRC R403.1.4 says exterior footings shall be placed not less than 12 inches below the undisturbed ground surface, and shall also conform to frost protection where applicable ⁴.

IRC R403.1.4.1 says foundation walls, piers and other permanent supports shall be protected from frost by one or more methods: extended below the frost line in Table R301.2, constructed under Section R403.3 for frost-protected shallow foundations, constructed under ASCE 32, or erected on solid rock.

It adds that footings shall not bear on frozen soil unless the frozen condition is permanent ⁴.

IRC R403.3 allows footings to stay above the frost line when protected by insulation per the code’s figure and table, for buildings kept at a minimum monthly mean temperature. It says such foundations shall not be used for unheated spaces such as porches, utility rooms, garages and carports ⁴.

These sections are quoted from Seattle’s 2021 residential code, which reproduces the 2021 IRC with local amendments. The frost line in Table R301.2 is filled in by each jurisdiction, so check the code and the frost depth your building department adopted.

Frost depth is local

The model code does not set one national frost depth. Each jurisdiction lists its own in the climatic design table. Ask your building department for yours before judging any footing.

Frost heave vs. other soil movements

Movement	Cause	When it happens
Frost heave	Ice lenses in freezing, wet, susceptible soil ²	Cold weather; thaw weakens soil after ³
Expansive clay swell	Clay minerals take up water ³	Wet periods; see seasonal soil moisture changes
Settlement	Soil compresses under load	Over time; see foundation settlement
Differential movement	Parts of a foundation move by different amounts	Any of the above; see differential settlement
Erosion loss	Water carries soil away from support	Heavy runoff; see soil erosion around foundations

Common myths about frost heave

Myth Frost heave is just water expanding when it freezes.: Reality In susceptible soil, the lift is driven by ice lenses fed by water drawn up from below ².
Myth Only northern states have frost heave.: Reality Any area with freezing ground, water and susceptible soil can have it. Local frost depth decides.
Myth A footing below the frost line makes every part of a property immune.: Reality Unheated attachments and shallow slabs, steps and porches can sit in the freezing zone, and the code limits frost-protected shallow designs to warm buildings ⁴.
Myth Sand and gravel heave like clay.: Reality NRCS rates very gravelly and very sandy soils among the least susceptible ³.
Myth If it comes back down in spring, it did no harm.: Reality Repeated uneven cycles can crack and tilt structures ².

Where frost depth and soils change the picture

Frost heave is a regional problem. Frost depth is a local number in a code table, and winter severity, snow cover and groundwater differ widely ⁴. NRCS notes that its susceptibility ratings assume soil not insulated by vegetation or snow and not artificially drained ³.

Cold, wet places with silty soils and high winter water tables face the greatest exposure, by the NRCS description. Ask your building department for the adopted frost depth and any local rules on frost-protected shallow foundations.

When frost heave matters, and what to do next

Frost heave matters when you plan a deck, porch, addition or garage slab in a cold region, when a structure rises and falls each winter, and when you buy a house with an unheated attachment. Start by asking what depth the footings reach and what your area’s frost line is.

For existing movement, record it through a full winter and thaw, keep water away from the area, and call an engineer if it does not recover. Try the foundation type identifier to confirm what supports each part of your house.

Decision guide What to do about winter lifting

If A porch or slab rises in winter and returns in spring: Then Photograph it, keep water away, ask a local pro about footing depth
If Movement stays after the thaw or cracks grow: Then Call a licensed structural engineer
If Planning a new porch, deck or addition: Then Ask the designer for the local frost depth and footing plan

Questions about Frost Heave

What causes frost heave?

Three things together: freezing temperatures in the soil, a source of water, and soil that lets water move to the freezing front. Water is drawn to growing ice lenses, which lift the ground. Remove any one condition and the heave stops.

What soils are most prone to frost heave?

NRCS says silty soils and highly structured clay soils with a high winter water table are the most susceptible. Well drained, very gravelly or very sandy soils are the least susceptible. A site test gives a better answer than a map rating.

How do footings avoid frost heave?

The model code lets footings be protected by going below the frost line, by frost-protected shallow foundation design with insulation, by following ASCE 32, or by sitting on solid rock. The frost line is set locally by each jurisdiction.

Can frost heave damage my house foundation?

It can, mainly where supports are shallow or unheated, such as porches, slabs on grade and additions. Uneven lifting can crack and tilt structures. A heated house on a footing below frost depth is generally protected, but check with an engineer if you see movement.

Does frost heave go away in spring?

The lift often relaxes as the ground thaws, but the thaw also weakens the soil, since melted ice lenses raise water content. Repeated uneven cycles can leave cracks and gaps. Record the movement and compare it after the thaw.

Can drainage prevent frost heave?

Drainage helps because it cuts the water supply that feeds ice lenses. Minnesota researchers list lowering the water table among the defenses. Drainage work must follow local rules on discharge, and it is not a guarantee, so ask a local engineer.

Is a frost-protected shallow foundation allowed everywhere?

No. It depends on the code edition your jurisdiction adopted, and the model code limits it to buildings kept at a minimum monthly mean temperature. It says such foundations shall not be used for unheated spaces like porches and garages.

How do I know if a crack is from frost heave?

You cannot tell from one crack. Frost heave tends to show up in winter at shallow or unheated parts of a structure and may recover on thaw. A licensed engineer reads movement history, water and site conditions before naming a cause.

Should I dig down to check my frost depth?

No. Digging next to a foundation can undermine it and trenches can collapse. Ask your building department for the adopted frost depth, or an engineer to review your footing records.

Sources

FEMA, Hurricane and Flood Mitigation Handbook for Public Facilities, Fact Sheet 3.1: Foundations (March 2022), retrieved October 14, 2026.
University of Minnesota, Voller, Hou and Sterling, Progressive Lifting of Shallow Sewers Due to Frost Heave Actions, MN/RC 2003-25 (August 2003), retrieved October 14, 2026.
USDA NRCS, Technical Guide Section II: Soil Interpretations, Engineering (May 2008): potential for frost action, retrieved October 14, 2026.
City of Seattle, 2021 Seattle Residential Code, Chapter 4 Foundations (2021 IRC text with Seattle amendments), retrieved October 14, 2026.
Penn State, Singh and Scanlon, Concrete in Residential Construction, 1st Residential Building Design and Construction Conference (2013), retrieved October 14, 2026.

Expert review

Written by the HyreFoundation Research team. Not yet reviewed by an outside expert. We say so rather than imply a review that has not happened; see our editorial policy.

How the numbers were checked: The three conditions and the mitigation list are from a University of Minnesota research report. Susceptibility classes are from the NRCS Technical Guide.

Code text comes from Seattle’s 2021 residential code, which reproduces the 2021 IRC with city amendments, and Penn State’s residential concrete paper. No frost depth, price or movement threshold is stated. The example porches are invented and labeled.

Suggest a correction. We fix errors and say what changed.