Can You Build Here? Soil Limits for Houses and Basements
Soil decides how hard and how costly a house is to build. USDA rates soils for houses by whether they carry the load without moving and by what excavation and construction will cost[1]. Enter an address to see USDA’s ratings for the typical soil there.
US addresses only: street address, city and state, or ZIP.
Example result · Alachua County, Florida
Houses with basements
Very limited
One or more features are unfavorable. Limitations generally cannot be overcome without major soil reclamation, special design or expensive installation. Poor performance and high maintenance can be expected.
Why
Depth to saturated zone1.00
Wet, Ground Water Near the Surface (75 - 180cm)
Each reason is scored from 0 (not a limitation) to 1 (greatest negative impact on the use).
Rating for Blichton (70% of this map unit)
Houses without basements
Very limited
One or more features are unfavorable. Limitations generally cannot be overcome without major soil reclamation, special design or expensive installation. Poor performance and high maintenance can be expected.
Why
Depth to saturated zone1.00
Wet, Ground Water Near the Surface (45 -75cm)
Each reason is scored from 0 (not a limitation) to 1 (greatest negative impact on the use).
Rating for Blichton (70% of this map unit)
Small commercial buildings
Very limited
One or more features are unfavorable. Limitations generally cannot be overcome without major soil reclamation, special design or expensive installation. Poor performance and high maintenance can be expected.
Why
Depth to saturated zone1.00
Wet, Ground Water Near the Surface (45 -75cm)
Slope0.88
Sloping 3.9 to > 8%
Each reason is scored from 0 (not a limitation) to 1 (greatest negative impact on the use).
Rating for Blichton (70% of this map unit)
Shallow excavations
Very limited
One or more features are unfavorable. Limitations generally cannot be overcome without major soil reclamation, special design or expensive installation. Poor performance and high maintenance can be expected.
Why
Depth to saturated zone1.00
Wet, Ground Water Near the Surface (75 - 180cm)
Unstable excavation walls0.01
Unstable Excavation Walls, revised
Each reason is scored from 0 (not a limitation) to 1 (greatest negative impact on the use).
USDA rates soils for building: houses with and without basements, small commercial buildings and shallow excavations. Each rating (not limited, somewhat limited or very limited) comes with the soil features behind it, such as depth to a water table, shrink-swell, slope or depth to bedrock[1].
The four building ratings
Dwellings are single-family houses of three stories or less; small commercial buildings are under three stories with no basement; shallow excavations are trenches or holes dug to 5 or 6 feet. What NRCS assumes for each use, and what the rating weighs[1]:
Use
What NRCS assumes
What the rating weighs
Houses without basements
Spread footings on undisturbed soil 2 ft down, or at the deepest frost penetration if deeper
Whether the soil carries the load without moving, and the cost of excavation and construction
Houses with basements
Spread footings on undisturbed soil about 7 ft down
The same as without a basement
Small commercial buildings
Under three stories, no basement; footings as for a house without a basement
The same as for houses
Shallow excavations
Trenches or holes dug to 5 or 6 ft, for utility lines, graves or open ditches
How easy the digging is, and whether the walls slough
3 stories: USDA’s dwelling ratings cover single-family houses of three stories or less[1].
Rating classes
NRCS defines each class, and scores every reason from 0.00, not a limitation, to 1.00, the greatest negative impact on the use[1]:
Class
USDA definition
Not limited
Features are very favorable for this use. Good performance and very low maintenance can be expected.
Somewhat limited
Features are moderately favorable. Limitations can be overcome or minimized by special planning, design or installation. Fair performance and moderate maintenance can be expected.
Very limited
One or more features are unfavorable. Limitations generally cannot be overcome without major soil reclamation, special design or expensive installation. Poor performance and high maintenance can be expected.
Not rated
USDA does not rate this soil for this use.
Why basements get their own rating
NRCS assumes a basement’s footings sit about 7 feet down and a house without one on footings about 2 feet down, or at the frost depth, and depth to a water table is one of the properties that decide whether the soil carries the load[1]. So a seasonal water table between those depths can count against the basement and not the slab.
A basement reaches deeper than a slab or crawl space, so a seasonal water table can reach it first.
Shallow excavations and caving walls
USDA rates trenches by how easy they are to dig and how well their walls resist sloughing. Bedrock or a cemented pan, large stones and dense layers make digging and filling harder; a high water table, flooding and ponding can limit when you can dig; slope affects the machinery; and texture, the water table and shrink-swell decide whether the walls cave[1].
A utility trench with one wall caving in, a water table near the bottom and bedrock below.
Worked example
Blichton sand in Alachua County, Florida (70% of its map unit): USDA rates it Very limited for all four uses. The main reason is ‘Depth to saturated zone’, scored 1.00, with the seasonal water table as shallow as 6 in (15 cm); small commercial buildings add 'Slope', scored 0.88[2]. The example result above shows each rating with its reasons.
What to do next
These ratings describe the typical soil USDA mapped for the area, at survey scales of 1:12,000 to 1:63,360 meant for planning[2]. Use them to see what to look into, then have a geotechnical investigation of your lot before you build. The water table depth and expansive soil checkers show two of the usual reasons in more detail.
Ways people use this
Buying a lot or a house with a basement.
Planning an addition or a new basement.
Siting a small commercial building or a long trench.
How we calculate this
We read USDA’s ratings for dwellings with and without basements, small commercial buildings and shallow excavations, with their reasons and scores, for the main soil at your point, plus any state building ratings for the same soil[2]. The class meanings are NRCS’s[1].
Frequently asked questions
Why can a lot be limited for basements but not without them?
NRCS assumes basement footings about 7 feet down and other house footings about 2 feet down, or at the frost depth[1], so a water table or bedrock between those depths can count against the basement only.
What do the reason scores mean?
Each is a score from 0.00, not a limitation, to 1.00, the greatest negative impact on the use[1].
Does 'very limited' mean I can't build?
It means building there needs major soil reclamation, special design or expensive installation, and NRCS expects poor performance and high maintenance[1].
What is a shallow excavation?
A trench or hole dug to a maximum depth of 5 or 6 feet, for graves, utility lines, open ditches or other purposes[1].
What is a state rating?
Some states add their own building ratings to the soil survey, such as Texas’s rating for pier and beam foundations; the checker shows them under the national ones[2].