Gravel, Stone, Soil and Mulch Delivery in Durham, NC

Built-over ground on Triassic basin rock

At the center point of ZIP 27701, the soil survey maps Urban land and rates 100 percent of the unit as paved or built over. Downtown ground has been graded, filled and built on for a long time, so a dig is more likely to turn up old fill, brick and gravel than a natural soil profile.^[1]

Beneath the city, the geologic map places the center point in the Chatham Group of the Newark Supergroup, rock of Triassic age. That group is made of conglomerate, sandstone and mudstone laid down in an ancient basin.^[2]

Mudstone weathers into fine, sticky clay, and soils formed from it can hold water and drain slowly. Where native ground shows up between buildings, expect a clayey layer that turns slick in wet weather and hard as brick in a dry spell.^[2]

The ground at the center point stands 400 feet above sea level. The land around it rolls, so many lots have some slope, and runoff from roofs and paving follows that slope toward the low side of the property.^[3]

Before any project, dig a test hole where the work will go. Clean, firm fill is easy to build on. Soft, wet clay calls for fabric and a thicker base, and loose rubble should come out so it does not settle later.^[1],[2]

Conglomerate and sandstone in the Chatham Group weather into sandier, coarser soil than the mudstone does. So two lots a few blocks apart can have very different ground, from sandy and quick to drain to clayey and slow.^[2]

Rain in every season and a real winter

The nearest NOAA normals station is Durham, about 5 miles away. It averages 48.6 inches of precipitation a year, with rain spread through all four seasons. Surfaces that trap water stay soft for long periods, so drainage is the first thing to plan.^[4]

The Durham station records 84 days a year with a low of 32 F or colder. Its median last spring freeze falls on April 2, and its median first fall freeze on November 4. Wet clay that freezes can lift pavers and stones, so a base that drains is the best defense.^[4]

Summer storms can be heavy and quick. On clayey ground, water from a sudden downpour runs off before it soaks in, and it can cut channels through a loose gravel path or wash mulch out of a sloped bed.^[4]

Clay soil is best worked when slightly damp. Right after a soaking rain it smears and clumps, and after a long dry spell it is too hard to dig. Plan grading for a few days after a rain.^[2],[4]

Spring thaw leaves clay soft for a while. Heavy equipment or loaded wheelbarrows on wet clay leave ruts that dry hard and stay all summer, so it pays to wait for firm ground before starting base work.^[2],[4]

A parking pad on clay or old fill

Clear the area of loose fill, roots and soft soil until you reach firm ground. On clay, lay a woven geotextile over the subgrade. The fabric keeps the base from sinking into wet clay and keeps clay from creeping up into the stone.^[1],[2]

For the main layer, Road Base packs into a firm, binding layer that carries cars well. Lay it in thin lifts and compact each one. On soft or wet spots, a lower layer of 1-1/2" Crushed Gravel adds strength and drainage.^[2],[4]

Top the pad with 3/4" Crushed Stone or Driveway Gravel. Give it a slight crown or a steady fall so rain runs off, and send that water toward a bed, a lawn or a strip of Drain Rock rather than the house.^[3],[4]

On a sloped lot, use Road Base for the surface as well as the base, since binding fines resist washing better than clean stone. Angled strips of Drain Rock across a long drive move runoff off before it builds speed.^[3],[4]

Alley pads behind older homes often sit lower than the alley itself, so water runs onto them. Build the pad up with extra base until it sits at or a little above the alley, and slope it back out so storm water drains away.^[3],[4]

Gravel paths and pads near brick walls should sit a little below the lowest course of brick, so splashing rain and soil do not wet the masonry. A narrow band of River Rock right against the wall keeps mud from splashing up in storms.^[4]

Beds and yards on small downtown lots

Fill and clay make poor planting soil. Raised beds filled with Garden Soil, or Topsoil blended with Compost, give plants a fresh start. In the ground, dig Compost deeply into the clay to loosen it and help water soak in.^[1],[2]

Mulch protects beds through heavy rain and cold snaps. Brown Shredded Mulch, Black Shredded Mulch and Red Mulch are common choices. Spread it after the median last spring freeze in early April, and add a fresh layer before early November.^[4]

Where water collects after a storm, a French drain of Drain Rock and a perforated pipe, wrapped in fabric, can carry it away. Lead the pipe to a lower part of the lot or to the street.^[2],[4]

For paths between beds, a layer of Stone Dust Screenings under Walkway Gravel or 3/8" Crushed Stone makes a firm surface that dries out faster than bare clay.^[4]

Shade trees are common on older blocks, and grass struggles under them. A bed of Wood Chips under the canopy protects the roots and breaks down into the clay over time, improving it a little each year.^[2]

Vegetable gardens on clay benefit from beds raised a hand or two above the ground. Filled with Garden Soil and topped with Compost each spring, they drain after heavy rain and warm up sooner after the last freeze.^[2],[4]

Downtown housing and the NCDOT base

Census data counts 14,073 housing units in ZIP 27701. Detached single-family houses make up 36 percent of them, below the 51 percent share across Durham.^[5]

The median home in this ZIP was built in 1975, older than the city median of 1995. Owners live in 30 percent of the occupied homes in ZIP 27701. Durham counts 136,837 housing units in all.^[5]

Older homes and rowhouse blocks downtown lead to smaller jobs: a gravel parking pad off an alley, a paver patio behind the house, or new beds along a fence.^[5]

The North Carolina Department of Transportation specifies Aggregate Base Course in Section 520 of its Standard Specifications for Roads and Structures, January 2024. That section is written for state roads. It describes a graded stone layer, compacted in lifts, that carries traffic over softer ground.^[6]