Quick answer
A shallow foundation is one that passes a building’s load to soil near the surface through footings, a slab, a crawl space or a basement, while a deep foundation is one, such as a pile or drilled pier, that reaches through weak upper soil to firmer ground below.
Most houses sit on shallow foundations. Deep foundations are used when surface soils cannot carry the load, and they are also used as repair supports under an existing footing.
Quick facts
The key facts about Shallow Foundation vs. Deep Foundation, with sources:
- Federal classification
- FEMA says all foundations are classified as shallow or deep 1
- Shallow systems
- Column and pier footings, wall footings, slab-on-grade, crawl space, basement 1
- Deep systems
- Primarily piles 1
- What is most common
- Most homes outside coastal high-hazard areas are on shallow foundations 1
- Soil effect
- Weak soil needs a larger shallow footing; bearing capacity matters less for piles 1
- Cost trade
- FHWA, writing about road and embankment work, calls a deep foundation an effective, usually much more expensive way to bypass compressible soils 2
- Swelling soil practice
- Colorado recommends drilled piers and grade beams in moderately to highly swelling soils 3
Key takeaways
- FEMA says every foundation is either shallow or deep. Shallow includes footings, slabs, crawl spaces and basements. Deep means piles 1.
- Most homes are on shallow foundations, with the footing placed below the frost zone 1.
- Shallow foundations lean on the soil near the surface, so soil strength and moisture matter a great deal.
- Deep foundations pass through weak or moving soil to firmer ground. FHWA, in a manual on road and embankment work, calls this an effective but usually much more expensive way to bypass compressible soils 2.
- Swelling soils push some regions toward deep options. Colorado’s Geological Survey recommends drilled piers and grade beams for moderately to highly swelling soils 3.
- Deep supports are also added under existing footings in repair. That is a different job from building a deep foundation, and it needs engineering.
What “shallow” and “deep” mean
The two words describe where the load is handed to the ground. A shallow foundation hands it to soil close to the surface. A deep foundation hands it to soil or rock far below.
FEMA’s manual puts it simply: all foundations are classified as either shallow or deep. Shallow systems consist of column and pier footings, wall footings, slab-on-grade, crawlspace and basement substructures. Deep systems primarily include piles 1.
Most houses use the shallow kind. The manual adds that most residential buildings outside coastal high-hazard areas are supported on shallow foundations 1. The four common home types in our foundation definition are all shallow.
The line is not a fixed depth. A basement footing can be several feet down and still be shallow. What matters is how the load gets into the soil: by bearing on a footing near the surface, or by reaching to a deeper layer.
General information, not a diagnosis of your house
General information, not a diagnosis of your house. Which kind of foundation a house needs depends on soil, loads and code, which a geotechnical or structural engineer determines.
How each one carries load
A shallow foundation works by bearing. The footing pushes down on the soil beneath it, and the soil pushes back.
FEMA explains that the weight of the structure creates a vertical pressure under the footing that the soil must resist, and that soils with lower bearing capacity require proportionally larger foundations to spread the load 1. See soil bearing capacity for the idea.
A deep foundation works differently. FEMA says that for deep foundations such as piles, bearing capacity has less effect because most of the resistance to gravity loads is developed by shear forces along the pile 1.
The pile can also end on a firm layer. Either way, the load travels past the weak or changing soil near the surface.
Shallow footings sit in the zone where seasons act on the soil. That includes frost, drying and wetting. FEMA notes that footings are placed completely below the maximum frost penetration depth 1.
Deep foundations extend well beyond that zone. Colorado’s Geological Survey says placing the bottom of drilled piers well below the zone of seasonal moisture change minimizes the risk from moisture changes 3.
Cross-section of a footing, stem wall, sill plate and floor framing sitting on soil, with the load from the wall passing down through the footing into the soil.
Illustrative, not to scale, not a design. It shows the load passing from the wall down through a footing into soil close to the surface.
Two cutaways of a footing. Left: a steel push pier pushed down through a bracket under the footing to firm soil. Right: a helical pier with spiral plates screwed down through a bracket under the footing. Both go below weak upper soil.
Illustrative, not to scale, not a design. It shows two kinds of deep pier placed under a footing to reach firmer soil below. This is how deep supports are used in repair.
Types of shallow and deep foundations
| Class | Type | What it is | Where it appears |
|---|---|---|---|
| Shallow | Wall (strip) footing | A continuous wide base under a wall 1 | Under crawl space, basement and stem walls |
| Shallow | Column or pier footing | A separate pad under each pier or column 1 | Pier and beam homes; porches; decks |
| Shallow | Slab-on-grade | A concrete floor and edge at ground level 1 | Slab foundations |
| Shallow | Crawl space or basement | Walls and footings enclosing an under-floor space 1 | Raised-floor and below-grade homes |
| Deep | Piles | Long members driven, drilled or screwed down to firmer ground 1 | Sites where near-surface soil cannot carry the load 2 |
| Deep | Drilled piers with grade beam | Drilled shafts extended well below seasonal moisture change, with a grade beam on top 3 | Colorado’s swelling soil zones 3 |
Example: matching a site problem to a foundation approach
The table below links three kinds of site problems to the approach each source describes. These are teaching examples, not recommendations for any house.
| Site problem | What the sources say | Approach discussed |
|---|---|---|
| Strong, stable surface soil | Footings placed below frost depth can carry homes where soil is adequate 1 | Shallow foundation |
| Weak or compressible soil near the surface | FHWA, in a road and embankment manual, says a deep foundation is an effective but usually much more expensive way to bypass it 2 | Deep foundation, or ground improvement |
| Highly swelling clay | Colorado says drilled piers and grade beams are generally recommended; pad and grade beam or extended walls should not be used in highly swelling soils 3 | Deep foundation with void under the grade beam |
| Coastal high-hazard area | FEMA notes most homes outside these areas are on shallow foundations, and names piles as the primary deep system 1 | Engineers weigh deep systems here |
In real projects the soil, loads and code decide. A geotechnical investigation and an engineer’s design come before the choice.
Where each approach is used
Shallow foundations are used on most houses where the near-surface soil can carry the load. The adopted code sets footing depth and size, and the soil sets how large the footing must be 1.
Deep foundations are used where the near-surface soil cannot, or where seasonal soil movement is large.
The Colorado Geological Survey notes that in moderately to highly swelling soils, drilled pier and grade beam foundations are generally recommended, and piers must be anchored in the non-swelling soil zone to limit uplift 3.
FEMA names piles as the primary deep system, and notes shallow foundations are the norm outside coastal high-hazard areas 1.
There is also a repair use. Deep piers can be placed under an existing footing to carry load to a deeper layer. See foundation underpinning, push piers and helical piers. That is a repair decision for a licensed engineer, not a choice made from a glossary.
Shallow and deep: strengths side by side
Where shallow foundations help
Where deep foundations help
- Pass loads below weak or compressible soils, which shallow footings cannot do 2.
- Anchor below the zone of seasonal moisture change, which limits movement from swelling soil 3.
- Depend less on soil bearing at the surface, since resistance develops along the pile 1.
- Piles are FEMA’s named deep system for sites that cannot rely on near-surface soil 1.
Limits of each approach
A shallow foundation depends on the soil under it. If that soil is expansive, compressible or poorly drained, the footing can move. The Texas bulletin on expansive soils calls shrink-swell soils a very common cause of foundation problems 4. A shallow footing cannot escape that on its own; the design has to manage it.
A deep foundation is not a cure-all. FHWA, writing about road and embankment work, notes that such solutions are usually much more expensive and may limit the flexibility of future uses of the site 2.
Deep systems also have design details that matter: Colorado’s guidance calls for a void between the soil and the grade beam so swelling soil cannot push up on it 3.
And neither approach fixes water at the wall. Drainage, grading and gutters matter whichever type holds the house up.
Shallow or deep is not good or bad
It is a match between soil, load and cost. A well-designed shallow foundation can suit a site better than a poorly designed deep one. The question is which fits the site.
What drives the cost difference
We do not print prices. FHWA, in a road and embankment manual, says deep foundations are usually much more expensive than other ways of handling compressible soil, and may limit future flexibility on the site 2. The drivers are depth, number of piles or piers, soil conditions, equipment access, testing, engineering and local labor.
For a shallow foundation the drivers are footprint, footing size, frost depth, excavation and concrete volume. On a repair, the drivers are the cause, the number of support points, soil, access and engineering. See the cost guide and the pier count estimator for how scope is built.
How the choice is usually made
On a new build the sequence below is typical. It is a general outline, not a design.
- Find out what the soil is: Soil survey data and tests show whether soils are expansive, compressible or shifting 4.
- Define the loads: The building, its use and local wind, seismic, snow or flood loads.
- Check shallow options first: If soil bearing and movement are acceptable, footings below frost depth may serve 1.
- Consider deeper options: If not, an engineer considers piers, piles or ground improvement 2.
- Check cost and code: The chosen system must meet the adopted code and be buildable on the site.
- Inspect during construction: The soil at the bottom of each hole is checked before concrete goes in.
Care that applies to both kinds
Care for either foundation kind needs no digging or structural work.
- Keep gutters clear and downspouts discharging away from the house. Colorado guidance asks that roof runoff be carried at least 10 feet from the building 3.
- Keep soil sloping away from the house.
- Keep large trees and thirsty plants away. Colorado guidance uses 15 feet for trees on swelling soils 3. Our tree distance check helps you think it through.
- Photograph and date new cracks and note whether they change.
- Keep records of any engineering reports, soil tests and permits. They tell the next owner what the foundation was designed for.
Risks and when to call a structural engineer
Shallow foundations face frost heave, shrink-swell cycles and settlement of weak or poorly placed fill.
FEMA says frost-susceptible soils in contact with moisture and subjected to freezing temperatures can undergo very large expansions, strong enough to move and crack adjacent structures 1.
FHWA notes that uncontrolled fill can hide loose pockets that cause differential settlement 2.
Deep foundations face their own risks: piers that were not anchored below the swelling zone, voids left too small, or corrosion and damage over time. None of these can be judged from the surface.
Call a licensed structural engineer if movement is significant, widening or changing; if walls bow or are displaced; if doors and windows stick along with new cracks; or if you doubt safety. Our engineer guide explains the options.
No method fits every house
A deep support that suits one house can be wrong for the next. Underpinning design depends on loads, soil, installation and engineering assessment. Do not choose a repair method from a diagram or a sales visit.
What the codes require
In states that adopt the International Residential Code, chapter 4 sets footing and foundation rules, and sections for expansive soils point to the International Building Code. Texas’ bulletin says foundations on expansive soils must be designed under IRC R403.1.8, which refers to IBC section 1808.6, and soil tests may be required under R401.4 where soils are expansive, compressible or shifting 4.
Those are 2015 numbers.
IRC R401.4.2, as summarized by Texas, offers alternatives to a full geotechnical evaluation when top or subsoils are compressible or shifting: remove the soil to a depth and width that gives stable moisture content, or stabilize it by chemical dewatering or presaturation 4.
Frost rules matter for shallow foundations. The 2018 IRC section R403.3 covers frost-protected shallow foundations, drawn partly from ASCE 32 5. Your jurisdiction decides the edition and the local frost depth. Always check with the building department.
Edition and adoption
Numbers above come from the 2015 and 2018 International Codes as summarized by Texas and ICC. Your jurisdiction may use a different edition or add amendments.
Shallow vs. deep at a glance
| Feature | Shallow foundation | Deep foundation |
|---|---|---|
| Where the load goes | Into soil near the surface 1 | Past weak soil to deeper layers 1 |
| What dominates behavior | Bearing capacity of near-surface soil 1 | Resistance along the pile and at its tip 1 |
| Most common for homes | Yes, outside coastal high-hazard areas 1 | Used where shallow options will not work 2 |
| Cost | Avoids the added cost of a deep system when soil is adequate 2 | FHWA calls deep systems usually much more expensive than other ways to bypass compressible soil (road context) 2 |
| Exposure to seasonal soil movement | Higher; frost, wetting and drying act near footings 13 | Lower when anchored well below the moisture zone 3 |
| Linked pages | Foundation footing | Drilled piers |
Shallow vs. deep myths
- Myth A deep foundation is always better.
- Reality FHWA, in a road and embankment manual, notes deep systems usually cost much more and can limit future flexibility. The right choice depends on soil, loads and code 2.
- Myth A shallow foundation is always weak.
- Reality Most homes are on shallow foundations 1. They work where soil and drainage suit the design.
- Myth “Deep” means a certain number of feet.
- Reality It is about how the load reaches the ground, not a set depth. A basement footing is deep in feet and still shallow in class 1.
- Myth Repair piers turn a shallow foundation into a deep one for good.
- Reality Repair piers add support at chosen points. The design depends on loads, soil, installation and engineering.
- Myth You can pick the type from a picture or a sales visit.
- Reality The choice rests on soil data, loads and code, which an engineer weighs.
Regional soil and frost factors
Regional soil and climate steer the choice. In Colorado, the Geological Survey says swelling soils or shales underlie much of the Front Range and recommends drilled piers and grade beams for moderately to highly swelling soils 3.
In Texas, the state’s bulletin treats expansive soils as a very common cause of foundation problems and sends designers to NRCS soil surveys 4.
In cold regions, footings must go below the frost zone or use frost-protected designs 15. Along parts of the Gulf Coast, groundwater pumping has caused subsidence, which affects foundation design too 6.
What to do with this
If you are planning a build, ask for a soil investigation before the foundation type is chosen. If you own a house and suspect movement, record what you see first. The repair method tool explains how methods differ in general, and the engineer-or-contractor tool helps decide who to call first.
- If Planning a new house
- Then Order a soil investigation and ask a designer about frost depth and soil movement
- If Buying a house with a known foundation repair
- Then Ask for the engineer’s report, the repair design and any warranty paperwork
- If Floors sloping or walls cracking and changing
- Then Call a licensed structural engineer
- If A sales visit that recommends deep piers
- Then Ask for an independent engineer’s assessment before you sign
Questions about Shallow Foundation vs. Deep Foundation
What is the difference between a shallow and a deep foundation?
A shallow foundation hands a building’s load to soil near the surface through footings, a slab, a crawl space or a basement. A deep foundation reaches down to firmer ground with piles or drilled piers. FEMA says all foundations are classified as one or the other, and that deep foundations primarily mean piles 1.
Is a basement a shallow or deep foundation?
FEMA lists basement substructures among shallow foundations 1. A basement footing sits deeper than a slab footing, but it still bears on soil near the surface and does not reach down through weak ground to a deep layer. Shallow versus deep is about how the load is carried, not the number of feet.
When is a deep foundation needed?
When near-surface soil cannot carry the load or moves too much. FHWA calls a deep foundation an effective but usually much more expensive way to bypass compressible soils 2. Colorado recommends drilled piers and grade beams for moderately to highly swelling soils 3. A geotechnical engineer makes the call.
Are most houses on shallow foundations?
Yes. FEMA’s manual says most residential buildings outside coastal high-hazard areas are supported on shallow foundations 1. That includes slab-on-grade, crawl space, basement and pier and beam homes, all of which use footings or slabs that bear on soil near the surface.
What is a spread footing?
A spread footing, or spread footing pad, is a shallow footing that spreads load from a column or pier over a larger area of soil. FEMA notes that isolated spread footings typically require reinforcing bars near the bottom 1. It is one of the shallow foundation types.
Do deep foundations stop all foundation movement?
No. They can reduce movement from near-surface soil, but they do not guarantee no future movement. Design depends on loads, soil, installation and engineering assessment. Anchoring and detailing matter; Colorado’s guidance calls for a void under the grade beam so swelling soil cannot push up on it 3.
Are piers for foundation repair deep foundations?
They reach deep to carry load, but they are added under an existing footing as a repair, not built as the original foundation. Whether a repair is appropriate depends on loads, soil, installation and an engineer’s assessment. See our concrete pier repair term for one method.
How deep must a footing be?
FEMA says footings should be placed completely below the maximum frost penetration depth, and local codes generally set that depth 1. Soil, loads and the type of foundation also matter. Your building department and the plans give the number for your house.
Sources
- FEMA P-259, Engineering Principles and Practices for Retrofitting Flood-Prone Residential Structures, 3rd ed. (Jan. 2012), retrieved .
- FHWA, GEC 013 (FHWA-NHI-16-027), Ground Modification Methods Reference Manual, Vol. I (Apr. 2017), retrieved .
- 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 .
- International Code Council, 2018 IRC Significant Changes (sample: frost-protected shallow foundations and crushed stone footings), retrieved .
- U.S. Geological Survey, Fact Sheet 165-00, Land Subsidence in the United States (Dec. 2000), 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 FEMA, FHWA, USGS, state and geological-survey documents listed above, retrieved 2026-10-14. Code numbers are from the 2015 and 2018 International Codes as quoted by those sources. No structural or geotechnical engineer has reviewed this page.
Suggest a correction. We fix errors and say what changed.