Slope and grade
Slope is a measurement, in percent, of the rise in height over the distance measured across the ground. Grade is the same rise-over-distance measure applied to a road, a driveway, a building pad or another designed or finished surface.
Slope reads the ground, grade reads what is built on it
The Virginia Department of Forestry defines slope as a percent measurement: the increase in height over the distance measured. Grade adds a purpose to that number. It is the same measure, taken along a road, a drive, a building pad or any surface someone has designed or finished.
A term of measurement in percent and means the increase in height over the distance measured.
Virginia Department of Forestry glossary, Slope
The arithmetic is simple when the distance is taken horizontally, rise over run. Ground that rises 20 feet over 100 feet has a 20 percent slope, and ground that rises one foot for every foot has a 100 percent slope, which is a 45 degree angle, not a wall. A percent is not a count of degrees, so check which one a map or a description is using.
Grade is where the same arithmetic meets something built. Floyd County's land division ordinance defines grade as the slope, rise over run, of a road or other public way, given in percent and shown on road profile plans. Where the building official requires a site plan under Virginia's building code, it shows grades of two kinds: the established street grades and the proposed finished grades.
Slope says how steep the ground is. It says nothing about which way the ground falls; that direction is a separate term, the aspect of a slope.
From a sketch plat to a county comprehensive plan
In a land deal in Southwest Virginia the two words show up in three kinds of document, and each uses them at a different scale.
- A sketch plat. Floyd County's land division ordinance lets a divider submit a sketch plat for the agent's early review before the engineered preliminary and final plats, and asks that sketch to show the approximate location of natural features such as slopes with approximate gradients. The word approximate matters: it marks where steep ground is, not a surveyed figure for every square foot.
- A site plan. Under the Uniform Statewide Building Code, when the building official requires one, a site plan shows to scale the proposed construction, distances from lot lines, the established street grades and the proposed finished grades. Who prepares one is covered in what a site plan is and who draws it.
- A county comprehensive plan. Carroll County's 2024 plan says slightly more than half of the county's land has a slope in excess of 20 percent, with most of the county in the Blue Ridge Physiographic Province, a mountain plateau of moderate to steeply rolling land. Grayson County's 2024 plan says over 60 percent of its land slopes more than 20 percent, and calls steep slopes a building challenge that takes grading, cut and fill, and measures for stormwater runoff and erosion.
Those county figures describe a whole county, not any one tract. A parcel in either county can be mostly gentle or mostly steep. On a road the grade is a different concern again: how steep the way in is bears on how a tract is reached and used, which is taken up in how mountain roads affect what land is worth.
Contours from aerial data are for a first look
An online contour map is a quick way to see where the steep ground is. Virginia law limits what some of those maps may be used for.
Under Va. Code 54.1-402, topography or contours determined with photogrammetric methods or similar remote-sensing technology by people not licensed as land surveyors are for general information only. They may not be used to design, modify or construct improvements to real property, or to determine a flood plain. A map like that is fine for seeing where the ground falls before a walk. A slope percent that a house or a drive will be designed around is a question for a land surveyor's topography.
Whether a given slope can carry a house is its own question, answered in whether you can build on a steep lot. How slope, the direction ground faces and siting fit together on a whole tract is laid out in slope, aspect and building.
Reading the slope on a parcel you are weighing?
Send the county and the road, or the plat book and page, and Lowell will point to what the plat and the county maps show about the steep ground and which figures still need a surveyor. No cost, no obligation.
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Questions about this term
Is the gradient on a sketch plat the same as a finished grade?
No. Floyd County's land division ordinance asks a sketch plat to show the approximate location of natural features such as slopes with approximate gradients, which describes the ground as it lies. A finished grade is a designed figure: where the building official requires a site plan under the Uniform Statewide Building Code, it shows the established street grades and the proposed finished grades.
Where this page's facts come from
Every rule, office and figure above traces to one of these. Rules change; check the office before you act on one.
- Glossary: Slope Virginia Department of Forestry
- Land Division Ordinance, effective January 1, 2026 (sketch plat contents and the definition of grade) Floyd County, Virginia
- 13VAC5-63-90, Uniform Statewide Building Code Section 109: construction documents and the site plan Virginia Administrative Code
- 2024 Comprehensive Plan (slopes and physiographic provinces) Carroll County, Virginia
- Comprehensive Plan 2024 (slopes and development) Grayson County, Virginia
- Va. Code 54.1-402: exemptions, and contours from photogrammetric methods Virginia General Assembly