Quick answer
Seasonal soil moisture changes are the rise and fall in the water content of the ground through the year, driven by rain, snowmelt, heat, plants and drainage, and in clay soils they make the ground swell when wet and shrink when dry.
A foundation rests on that ground. Where the moisture swings are large or uneven, parts of the foundation can rise or drop by different amounts. The change in moisture, more than the soil type alone, sets how much movement occurs.
Quick facts
The key facts about Seasonal Soil Moisture Changes, with sources:
Key takeaways
- Soil water content rises and falls through the year, and clay soils change volume with it 12.
- High moisture makes expansive soil swell and lift a building. Low moisture makes it shrink and can let a building settle 2.
- Uneven movement does the damage. Uneven moisture, from drainage, watering, plants or covered ground, makes movement uneven 1.
- Changes in soil moisture are named as the leading cause of foundation heave or settlement on swelling soils in one Army Corps report 3.
- Surface drainage, plant choices, sprinkling habits and upkeep all help steady soil moisture 2.
- A record of cracks and floor levels over several seasons helps a professional read what is happening.
What seasonal soil moisture changes are
Ground is not a dry block. It holds water in the tiny spaces between grains and, in clay, between the layers of the clay minerals themselves.
Spring rain, summer heat, autumn storms and winter snow all change how much water is there. In sand and gravel, that matters little for volume. In clay with swelling minerals, it matters a great deal.
The Colorado Geological Survey explains that soil properties set the potential for swell, while environmental conditions that change soil moisture set the actual amount and rate of swelling or shrinking under a structure 1. The same ground can behave differently in a wet year and a dry year.
This page covers the yearly cycle. For the clay itself, read expansive clay soil. For the upward movement, see foundation heave.
General information, not a diagnosis of your house
General information, not a diagnosis of your house. Soil type, depth, drainage, trees and the foundation design all change how much a seasonal swing matters.
How moisture swings move a foundation
Clay minerals attract water. The Colorado guide says the flat clay plates are pushed farther apart as more water is made available, and that the pressure and movement from this volume change cause most swelling-soil damage 1. When the soil dries, the plates draw together and the soil shrinks.
Texas guidance states the result in building terms. Expansive soils with high moisture levels will heave, which lifts a building, and soils with low moisture levels will collapse, which causes settlement 2. Both can cause extensive damage.
Why does a house crack, not just rise or fall? Because the soil rarely changes evenly. The Colorado guide says differential movement is usually caused by non-uniform changes in soil moisture and irregularities in the thickness and makeup of the clay layers.
It names edge effects of wetting or drying on a covered area, drainage patterns, local watering, evaporation, and shrubs and trees that remove soil moisture 1. A house is covered ground, so its center stays steadier than its edges.
Two panels. Left: wet clay soil has swollen and lifts the edge of a slab. Right: dry clay soil has shrunk and left a gap under the slab edge. Arrows show swelling and shrinking.
Illustrative, not to scale, not a design. It shows soil rising under a foundation when wet and dropping away when dry, with no depths or amounts drawn.
What changes soil moisture around a house
| Driver | How it acts | Source |
|---|---|---|
| Weather cycles | Wet and dry spells, seasonal or longer, raise and lower soil water | Colorado Geological Survey 1 |
| Drainage patterns | Water that collects near the wall keeps soil wet there | Colorado Geological Survey 1 |
| Local watering | Sprinklers and hoses add water to nearby soil | Colorado Geological Survey 1 |
| Evaporation | Drying at the surface and from open soil lowers moisture | Colorado Geological Survey 1 |
| Shrubs and trees | Roots remove soil moisture by transpiration | Colorado Geological Survey 1 |
| Covered ground | Slabs and paving block evaporation, so the middle stays wetter than the edge | Army Corps report; Colorado 31 |
| Poor drainage after construction | Water that was not planned for ends up in the soil | Army Corps report 3 |
Example: wet and dry seasons acting on a slab
A 2006 study by El-Garhy and Wray modeled a slab-on-ground house on expansive soil under three moisture conditions 4. The table restates their scenarios in plain words. It gives no numbers because their numbers belong to the model, not to your house.
| Condition modeled | What happens to soil near the slab edge | Pattern of movement |
|---|---|---|
| After a long wet period | Edge soil swells | Edges tend to rise relative to the center 4 |
| After a long dry period | Edge soil shrinks | The center tends to stand higher than the edges 4 |
| A dry spell starting from a balanced state | Edge soil shrinks from an even start | The authors compared the resulting movement; see their paper for results 4 |
The same idea shows up in the field. The Colorado guide describes two homes built side by side on highly swelling soil in 1977 and 1978.
One was built in a dry spring and had more potential for damage from swell. The other was built in a wet spring and had more potential for damage from shrinkage 1. The weather at construction time matters.
Where moisture swings do the most harm
The swing is strongest near the edges of a house, under porches and patios, along drives, and beside beds that are watered often. These are the spots where wet and dry ground sit side by side.
A tree near one corner can dry that corner while the rest of the ground stays damp. The Colorado guide notes that shrinkage may follow a wet-weather construction period if dry cycles come later, or may come from moisture-loving trees or shrubs near the foundation 1.
The effect also reaches below the surface layer. The Colorado guide recommends drilled-pier foundations in moderately to highly swelling soils because placing pier bottoms well below the zone of seasonal moisture change cuts the risk of moisture changes affecting the foundation 1.
That tells you the zone is real, and that a house on a shallow footing sits inside it.
Source: [1]
Why understanding the cycle helps
What it helps you do
- Explains why cracks and floor slopes can change with the weather.
- Points to practical levers: drainage, plant choices and sprinkling habits 2.
- Helps you time photos and level readings across seasons.
- Helps you talk with an engineer about soil testing and design.
What it cannot do
- Cannot tell you the soil type; a soil survey or test does that 2.
- Cannot say how much movement a house can tolerate; engineers set that for each project.
- Cannot undo movement that has already happened.
- Cannot replace a geotechnical report; see geotechnical soil investigation.
Limits of the seasonal idea
Not every soil moves with the seasons. Sand and gravel change little. Clay with a high content of swelling minerals changes a lot. Soil type is one input, and Texas guidance says the expansion ability of a soil is set by the percentage and type of clay 2.
Seasonal moisture is also not the only cause of movement. Fill that settles, frost, erosion and leaks can all move a house. Our foundation settlement entry covers the other main causes. A crack that opens in summer may have a different cause than one that opens in winter.
Finally, we cannot tell you how deep the seasonal zone is at your site. It varies with climate, soil and plants, and the sources we loaded do not give a figure to use.
Seasonal vs. one-time moisture change
A seasonal swing repeats each year. A leak, a new downspout dump or a cut tree is a one-time change that can move the soil in a different way. Both matter, but they call for different answers.
What drives the cost of managing moisture swings
We do not print prices. Low-cost steps include clearing gutters, extending downspouts, moving sprinklers and adjusting grade. Larger steps, such as a new drainage layout, tree work, a soil investigation or an engineer’s design, are driven by site size, soil, access and scope.
If movement has already caused damage, repair cost depends on the cause, extent and method, and an engineer’s findings should come first. Read our cost guide to see how quotes are built.
How to track what the seasons are doing
A homeowner routine. It records facts and does not diagnose.
- Pick fixed reference points: Choose a few cracks and a few door or window gaps to watch.
- Photograph and date them: Use the same angle and add a tape or card for scale.
- Repeat each season and after big weather: A long drought or a long wet spell is worth recording.
- Note what changed nearby: New irrigation, a removed tree, a new downspout or a leak all matter.
- Keep a log: The elevation log and the crack identification tool help organize it.
- Share the record: A structural engineer can use it to see whether movement follows the weather.
Ways owners can steady soil moisture
Steadying soil moisture takes surface steps. None involves digging beside the foundation.
- Keep surface water moving away from the wall with good slope and extended downspouts 2.
- Keep grass, shrubs and sprinklers back from the foundation; Colorado’s guide asks for at least 5 feet in swelling soils 1.
- Keep large trees at a distance; Colorado’s guide asks for at least 15 feet, and more for water-loving species 1.
- Watch sprinkler settings so they do not soak one side only 2.
- In high shrink-swell soil, do not fill and tightly compact cracks next to a basement wall when the soil is dry 5.
- Fix leaks quickly, since they add water in the wrong place.
Risks and when to call a structural engineer
Repeated swelling and shrinking can crack walls and slabs, tilt floors, and make doors and windows stick. The Colorado guide says differential heave, not total movement, is generally responsible for major structural damage 1. You cannot read the cause from one crack or one photo, so treat what you see as a clue.
Be careful with water as a fix. Adding water to dry soil at one point can create uneven moisture, and soil that is saturated can push on a basement wall. HUD’s guide says expansive clays in very moist conditions can place significant lateral loads on foundation walls 6.
Call a licensed structural engineer if cracks are widening or changing, if a wall bows or is displaced, if doors and windows stick along with new cracks, if corners separate, or if you doubt safety. Our engineer guide explains who to call.
Do not dig or flood the soil to fix movement
Digging beside a foundation can undermine it, and soaking dry soil without a plan can move the house the other way. Get an engineer’s read before you change moisture near a foundation in a major way.
What codes and agencies say
In states that adopt the IRC, foundations on expansive soil are tied to the IBC.
A Texas bulletin written for the 2015 editions says IRC section 403.1.8 requires such foundations to be designed under IBC section 1808.6, and that IRC R403.1.8.1 treats a soil as expansive when it meets listed tests, including a plasticity index of 15 or greater, or an expansion index above 20 2.
It also says IRC R401.4 allows soil tests in areas likely to have expansive, compressible or shifting soils 2.
Texas tells builders that water must drain away from the house on all sides, and tells owners that changes in drainage flow can cause damage 2.
The bulletin points to NRCS soil survey reports as a way to find where expansive soils lie. NRCS Web Soil Survey also estimates depth to the seasonal high water table for each map unit 7.
Edition and adoption
Section numbers above come from a bulletin written for the 2015 IRC and IBC. Later editions can renumber or revise them. Ask your building department which edition applies.
Seasonal moisture change compared with nearby ideas
| Idea | What it is | How it relates |
|---|---|---|
| Seasonal moisture change | Yearly rise and fall in soil water | This page 1 |
| Expansive clay soil | Clay that changes volume with moisture | The soil that reacts to the swings 2 |
| Foundation heave | Upward movement of a foundation | One result of wet-season swelling 2 |
| Foundation settlement | Downward movement of a foundation | Can follow drying of expansive soil 2 |
| Plumbing leak | A one-time source of extra soil moisture | Modeled by El-Garhy and Wray for a slab on expansive soil 4 |
Seasonal moisture myths
- Myth Foundation problems come only from drought.
- Reality Wet soil swells and lifts, and dry soil shrinks and settles. Both happen 2.
- Myth All soil moves with the weather.
- Reality Soil properties set the potential. Sand changes little, and swelling clay changes a lot 1.
- Myth A crack that opens in summer proves drying.
- Reality A crack is a clue. Movement history, water, construction and soil change what it means.
- Myth Watering the foundation always prevents cracks.
- Reality Sprinkling habits are one named lever 2, but uneven watering can create uneven moisture. Ask a local engineer for a plan.
- Myth A tree is harmless if it is not touching the house.
- Reality Roots remove moisture from the soil, and Colorado’s guide asks for tree distances of 15 feet or more 1.
Regional factors for moisture swings
The Colorado Geological Survey says Colorado’s semi-arid climate and geology make it one of the most severely affected areas for expansive soils, and that every major Front Range population center is underlain at least in part by swelling soils or shales 1.
Texas treats expansive soils as a very common cause of foundation problems 2. In Kansas, spring rains cause water-entry problems, and a seasonal high water table most often contributes to wet basements 5.
The Colorado guide notes that USGS has expansive-soil maps for some metropolitan areas 1, and NRCS soil surveys can also help; ask your building department for local rules.
What to do with this
Start by finding what water does near your house, and keep a seasonal record. If you plan to buy, our buyer checklist helps you look at drainage and trees. If movement is changing, our foundation inspection page explains what a professional examines.
- If Water pools near one wall after rain
- Then Fix slope and downspouts there first
- If A large tree sits close to one corner
- Then Ask an arborist and an engineer before pruning or removal
- If Cracks seem to follow wet and dry spells
- Then Photograph each season and share the log with an engineer
- If New or widening cracks, bowing, sticking doors
- Then Call a licensed structural engineer; do not dig
Questions about Seasonal Soil Moisture Changes
What are seasonal soil moisture changes?
They are the rise and fall of water in the ground through the year. Rain, heat, plants and drainage all change them. The Colorado Geological Survey says soil properties set the potential for swell, while environmental conditions that change soil moisture set the actual amount and rate of swelling or shrinking 1.
How do wet and dry seasons affect a foundation?
On expansive soil, wet periods make the soil swell and lift a building, and dry periods make it shrink and let a building settle 2. Because the soil rarely changes evenly, parts of the foundation can move by different amounts, which strains walls and floors.
Do all soils change with the seasons?
No. Soil properties matter. Texas guidance says a soil’s expansion ability is set by the percentage and type of clay in it 2. A soil survey or test shows which soil you have. Sandy or gravelly soils tend to change little with moisture.
Why do my cracks change with the weather?
They may be linked to soil moisture, but a crack is a clue, not a diagnosis. Movement history, water, construction details and soil all change what it means. Photograph and date cracks each season and share the log with a structural engineer if they are changing.
Should I water my foundation?
Sprinkling practices are listed by Texas guidance as one of several ways to limit swings in soil moisture 2. The right plan depends on soil, foundation and local rules, and uneven watering can backfire. Ask a local structural or geotechnical engineer before starting a watering routine.
How far should trees be from my house?
There is no universal rule. Colorado’s 1978 guide for swelling soils asks that trees be planted at least 15 feet from any building, and at least 20 feet for large water-loving trees 1. Read tree roots and foundation movement for why distance is only a screen.
Can drainage reduce seasonal movement?
It can help. The Colorado guide says drainage is extremely important because changes in moisture content cause both swelling and shrinking 1. Texas guidance lists surface drainage, plant choices, sprinkling practices and long-term upkeep as steps that minimize swings in soil moisture 2.
Is it safe to fill cracks in the soil beside the house?
Be careful. Kansas State warns that in areas of high shrink-swell soil you should not fill and tightly compact cracks next to the basement wall when the soil is dry, because the soil often expands when it is rewetted and can press hard enough to crack the wall 5.
How long does a seasonal cycle last?
The yearly cycle follows the seasons, but longer wet and dry periods also matter. The Colorado guide notes seasonal or cyclic (long time) weather changes as a source of moisture variation 1. Multi-year droughts and wet spells can move soils further than a single year.
When should I call a structural engineer?
Call one when movement is significant, widening or changing, when walls bow or are displaced, when doors and windows stick with new cracks, when corners separate, or when you doubt safety. A seasonal record of photos and readings will help the engineer see the pattern.
Sources
- Colorado Geological Survey, Special Publication 11, Home Construction on Shrinking and Swelling Soils (Holtz and Hart, 1978), retrieved .
- Texas Department of Licensing and Regulation, IHB Technical Bulletin TB 10-01, Foundations on Expansive Soils – Residential (rev. Oct. 16, 2018), retrieved .
- L. D. Johnson, U.S. Army Engineer Waterways Experiment Station, Overview for Design of Foundations on Expansive Soils, Misc. Paper GL-79-21 (1979), abstract record, retrieved .
- El-Garhy and Wray, Investigation of a leaking water line beneath residential foundation on expansive soils (2006), abstract record, retrieved .
- Kansas State University Agricultural Experiment Station and Cooperative Extension Service, MF2809, Dry Basements and Crawl Spaces, retrieved .
- U.S. HUD Office of Policy Development and Research, Residential Structural Design Guide, 2nd ed. (Oct. 2017), retrieved .
- University of Delaware Cooperative Extension, Using Web Soil Survey (fact sheet), retrieved .
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: Facts were checked against the Colorado Geological Survey, Texas TDLR, U.S. Army Engineer Waterways Experiment Station and Michigan Tech abstracts, Kansas State, HUD and University of Delaware documents listed above, retrieved 2026-10-14.
Code references come from a bulletin written for the 2015 IRC and IBC and may differ by edition. No structural engineer has reviewed this page.
Suggest a correction. We fix errors and say what changed.