Gravel, Stone and Soil Delivery in Asheville, NC

Steep clay loam over old gneiss

At the center point of ZIP 28801, the USDA soil survey maps Clifton-Urban land complex, 15 to 30 percent slopes. Urban land, meaning ground that is paved or built over, makes up 40 percent of the complex, and the Clifton series makes up 50 percent. A complex like this mixes the two in a pattern too fine to map apart, so one yard can hold native Clifton soil while the next holds fill and pavement.^[1]

Where Clifton soil remains, its top mineral layer is clay loam. The survey rates it well drained and places it in hydrologic group B, the moderate-infiltration class. Water moves into the ground at a fair pace, and the slope carries off whatever the soil cannot take in, often faster than a homeowner would like.^[1]

Shrink-swell in the top 100 cm sits at 4.5 percent, a moderate rating. Clay loam with that figure swells a little when soaked and shrinks a little when dry. On a level site that matters for slabs and footings. On a steep site it adds to the slow creep of soil downhill, which is one reason retaining walls here need a free-draining backfill.^[1]

The USGS state geologic map shows the Ashe Metamorphic Suite and Tallulah Falls Formation at the center point, with muscovite-biotite gneiss. The rocks listed for the unit are gneiss, mica schist and amphibolite, all Neoproterozoic. Weathered pieces of those rocks, flaky with mica, turn up in many local excavations.^[2]

The ground at the center point rises 2,130 feet above sea level, mountain country by East Coast standards.^[3]

Mountain rain and a moderate winter

Weather normals for ZIP 28801 come from the NOAA station at Asheville, NC. It averages 40.6 inches of precipitation and 11.5 inches of snow a year.^[4]

Lows at the Asheville station reach 32 F or colder on 77 days in a normal year. Many of those nights end in a thaw by midday, so the top inch of a gravel surface can freeze and loosen several times in a single week.^[4]

The median last spring freeze at the station falls on April 6, and the median first fall freeze on October 31. Garden planting, sod and seed are safest after the April date. Fall is a good window for hardscape work, since the soil is dry and there is time for stone to settle before the cold sets in.^[4]

Rain on a slope of 15 to 30 percent picks up speed fast. A summer thunderstorm can move loose gravel, mulch and soil downhill in a single afternoon, and the damage concentrates wherever water runs in a line, such as a driveway edge or a path down the hill.^[1],[4]

Holding a drive on a slope

A sloped gravel drive needs stone that locks. Rounded Pea Gravel and River Rock roll under tires on any grade, so save them for flat spots. Start with a cleared, compacted clay loam subgrade, lay woven fabric, and build a base of 1-1/2" Crushed Gravel or #4 Crushed Stone, then compact Road Base or Crushed Concrete over it in thin layers.^[1]

The top course should be Driveway Gravel or 3/4" Crushed Stone, packed firm. On the steepest stretches, Asphalt Millings can work better, since they bind into a mat that resists washing. Whatever the surface, water must leave the drive often. Cut shallow diagonal water bars across the drive every so often to turn runoff off the side before it gathers volume.^[4]

Where water bars and ditches empty, the flow hits bare ground hard. Riprap at each outlet breaks up the water and stops a gully from forming. A ditch lined with #57 Crushed Stone along the uphill side of a drive catches water coming down the slope before it crosses the gravel.^[1],[4]

Walls, steps and terraces

Steep lots in Asheville often get terraced for gardens or flat play space. A retaining wall on clay loam with moderate shrink-swell needs drainage behind it. Backfill the first foot behind the wall with Drain Rock or #57 Crushed Stone, wrap it in fabric, and set a perforated pipe at the base to carry water out the end.^[1]

Garden steps built from timbers or stone can use #67 Stone or Stone Dust Screenings as the tread fill. Screenings pack into a smooth step that drains, and #67 Stone gives better grip in wet weather. Each step should tip slightly forward so water runs off rather than pooling.^[1]

Rock dug from a cut bank on a hillside lot is often weathered gneiss or schist that crumbles under a boot. It looks solid in the bank but breaks down quickly as fill, so it makes a poor bed for a wall or path. Swap it for compacted Road Base wherever a structure has to sit.^[1],[2]

Built-over parts of the complex hold old fill, so dig test holes before setting a wall footing. A trench filled with compacted Road Base gives the footing a stable bed even where the native soil has been disturbed.^[1]

Gardens on clay loam

Clay loam holds nutrients well but packs hard when worked wet. Wait until the soil crumbles in the hand before digging in spring, which often lines up with the weeks after the April 6 freeze date. Mix Compost into the top layer of each bed to keep it loose.^[1],[4]

Mulch is the best defense against erosion on planted slopes. Brown Shredded Mulch, Black Shredded Mulch and Red Mulch interlock and stay put far better than loose chips. On the steepest beds, lay jute netting first, then the mulch over it.^[1],[4]

Raised beds of Garden Soil give vegetables a deeper root zone than the native clay loam. Topsoil levels terraces for lawns. Wood Chips cover woodland paths and break down slowly into the soil beneath them.^[1]

Mountain gardens can keep going well into autumn here. With the median first fall freeze on October 31 at the city station, a layer of mulch spread in mid-autumn keeps the soil warm for root growth after the tops have stopped.^[4]

Homes in ZIP 28801

Buncombe County contains ZIP 28801. The Census counts 9,014 housing units in the ZIP, and 43 percent of them are detached single-family houses.^[5]

Homes in ZIP 28801 have a median build year of 1963. Owners live in 37 percent of the occupied homes.^[5]

Asheville as a whole counts 50,034 housing units, with detached houses at 56 percent. The city's median year built is 1982.^[5]

Many projects in the ZIP involve shared or small spaces: a courtyard, a stair path between buildings or a narrow parking strip. A few tons of 3/4" Crushed Stone or a load of mulch covers most of these jobs.^[5]

The North Carolina Department of Transportation specifies Aggregate Base Course in Section 520 of its Standard Specifications for Roads and Structures (January 2024).^[6]