Driveway Gravel in Maryland: The Surface Course, Not the Base

A drive in Garrett County and a drive in Dorchester County come apart for opposite reasons. On the western plateau the soil is thin stony silt loam over shale and sandstone, county code sets frost at 36 inches, and the damage shows up at the thaw when a heaved surface softens. Out on the Shore the ground is sandy loam and silt with the water table close behind it, several counties set frost at 24 inches, and the damage shows up when flat land cannot shed a nor'easter fast enough. Driveway gravel serves both, and in both cases what decides the outcome is the layer underneath rather than the stone you can see.

What lands on the apron: angular 3/4 inch stone with the smaller sizes left in

The pile arrives looking coarse and uneven, and that is the point. Rounded stone rolls under a wheel; crushed stone locks. Spread it and run a car over it and the top half inch tightens within a week or two. It never goes hard the way a bound base goes hard, and it is not meant to.

The drives, parking pads and farm lanes driveway gravel was graded for

This is a surfacing material. It goes on top of a base that has already been shaped and compacted, and it does three jobs there: it takes the tire wear, it gives grip, and it lets rain through instead of holding it at the surface.

• A residential drive that has rutted and needs its profile back.
• A parking pad beside the house for a second car, a trailer or an RV.
• A farm lane or rear access track where pavement is not the plan.
• A turnaround beyond the garage, or the apron where the drive meets the county road and traffic turns hardest.

A rock garden, a shed pad and a splash strip: three jobs it will disappoint

A xeriscape or rock garden bed wants stone you are happy to look at from the kitchen window. Driveway gravel is graded for traffic, not for appearance, and the fines that help it knit are the same fines that dull it after a summer of rain. River Rock or 3/8" Natural Pea Gravel read better in a bed.

A shed or garage pad is carrying a static point load, not rolling traffic, and it wants a dense-graded layer that compacts and stays compacted. That is CR-6, with driveway gravel over it only if you want a loose finish around the doors.

A downspout splash area is a drainage detail. Fines wash out of the stone and glaze the soil under it, so the splash strip stops draining after a season or two. Clean washed stone such as #57 Stone holds its voids there.

Depth over Piedmont clay, depth over Eastern Shore sand

Two inches of new gravel on a sound existing drive is a top-up. Three to four inches is a resurfacing. Anything more than that on soft ground is stone being buried rather than stone being used.

• Central Maryland Piedmont: silt loam and clay loam over crystalline rock goes soft when saturated. Build the crown first so water leaves the drive sideways, then put three inches of gravel on a compacted base. A drive with no crown will rut again whatever you spread on it.
• Western Maryland: slopes deliver snowmelt and rain onto the drive rather than across it. Carry that water around the lane with a ditch or a cross drain before you add depth, and keep the surface course at the shallow end so it is not pushed downhill.
• Coastal Plain and the Eastern Shore: the base has to sit above wet ground. Where a lane stays damp after storms, the fix is drainage and a thicker base, not a deeper surface.
• Limestone ground near Hagerstown and Frederick: spread the runoff from the drive instead of funneling it to one point, since concentrated water is what opens depressions in that country.

Counting tons for a rock garden bed, a shed pad and four downspouts

Square feet times depth in feet gives cubic feet; divide by 27 for cubic yards; multiply by 1.40 to reach tons at the approximate weight above. Depth in inches divides by 12 first. All three are worked examples rather than real jobs.

• Rock garden bed, 18 feet by 11 feet at 2 inches: 18 x 11 = 198 square feet. 2 inches is 0.1667 feet, so 198 x 0.1667 = 33 cubic feet. 33 divided by 27 = 1.22 cubic yards, which is about 1.7 tons.
• Shed pad finished with a loose surface, 12 feet by 16 feet at 4 inches: 12 x 16 = 192 square feet. 4 inches is 0.3333 feet, so 192 x 0.3333 = 64 cubic feet. 64 divided by 27 = 2.37 cubic yards, about 3.3 tons. The compacted base beneath that pad is a separate order.
• Four downspout splash strips, each 6 feet by 3 feet at 3 inches: 6 x 3 = 18 square feet each, 72 square feet in total. 3 inches is 0.25 feet, so 72 x 0.25 = 18 cubic feet, divided by 27 = 0.67 cubic yards, about 0.9 tons.

Odd shapes split into rectangles, and a circle is diameter times diameter times 0.7854. For anything with a changing width, the gravel calculator will carry the depth and the conversion for you.

CR-6 underneath, finer stone where bare feet go

Three materials sit either side of this one in the list. Crusher Run and CR-6 are the compacting blends that belong below the surface course, and CR-6 is the term most Maryland yards use when they mean a dense-graded base. Walkway Gravel is the finer cousin for paths that are walked rather than driven. Measure the drive, take the cubic yards through the calculator, then pick your tonnage and a date on this page. If the lane changes width or has a hill in it, send the measurements through our contact page and settle the figure before you order.