Gravel, Stone and Soil Delivery in Allentown, PA

Built-over slopes on carbonate rock

The USDA soil survey maps the center point of ZIP 18101 as Urban land, 8 to 15 percent slopes. Within that unit, 90 percent of the surface is paved, built on or covered. The ground that is left has been cut, filled and graded many times, and yard soil can hold brick, cinders, old gravel and patches of clay.^[1]

Slopes of 8 to 15 percent mean water and loose material move downhill. A gravel area laid without edging or drainage on a grade like that can creep toward the street within a season or two.^[1]

Expect surprises in an old neighborhood. Abandoned pipes, old foundations and buried paving turn up often on lots that have been rebuilt several times, so have underground lines marked before any dig.^[1]

The USGS state geologic map places the Allentown Formation at the center point, a Cambrian unit of dolostone, limestone, siltstone and chert. Limestone and dolostone dissolve slowly in water over very long periods, and ground underlain by them can develop voids and sinkholes, especially where runoff is concentrated in one spot.^[2]

That makes drainage design more than a matter of keeping a basement dry. Spreading roof and yard water out, rather than pouring it into a single pit near a foundation, is the safer approach on carbonate rock.^[2]

At the center point, the ground stands 330 feet above sea level.^[3]

Rain, snow and many cold nights

Weather normals for ZIP 18101 come from the NOAA station at Allentown Intl AP, PA, about 3 miles away. It averages 47.4 inches of precipitation and 33.1 inches of snowfall a year.^[4]

Lows at the airport station drop to 32 F or colder on 118 days in a normal year. Each freeze can lift wet material and each thaw lets it settle, so a base holding water slowly comes apart over a winter.^[4]

Rain falls in every season here, so outdoor stone work has fewer dry windows than in a western climate. Piles of Road Base or Topsoil left in the open should be covered with a tarp so they stay workable.^[4]

Allentown Intl AP has a median last spring freeze of April 20 and a median first fall freeze of October 24. Plan seeding and planting for after the April date, and finish base and paving jobs with enough time before the October one for the stone to settle.^[4]

Snow shoveled off steps, walks and parking spots piles at the low side of a sloped lot, and its melt runs downhill across whatever lies below. A strip of washed stone at the base of a slope gives that water a place to go.^[1],[4]

Steps, terraces and parking on a grade

Sloped city lots often get terraced into a parking spot, a patio or a level garden. For a parking pad, dig out loose fill to firm ground, lay woven fabric and compact Road Base or Crushed Concrete in thin lifts. Driveway Gravel or 3/4" Crushed Stone makes the top course, and timber or steel edging on the downhill side holds it in place.^[1]

Garden steps cut into a slope can be filled with #67 Stone or Stone Dust Screenings. Screenings pack into a smooth tread, and #67 Stone gives better grip in wet weather. Tilt each tread slightly forward so water runs off.^[1]

On a narrow sloped lot, getting material to the work area is often the hardest part. Plan the drop spot at the top of the slope where possible, since wheeling stone downhill is far easier than pushing it up.^[1]

Retaining walls need free-draining backfill. Fill the first foot behind the wall with Drain Rock or #57 Crushed Stone wrapped in fabric, with a perforated pipe at the base. In a place with many freezing nights, water trapped behind a wall freezes and pushes it outward.^[1],[4]

Drainage on carbonate ground

With 47.4 inches of yearly precipitation at the airport station and most of the ground paved, runoff has few places to soak in. On limestone and dolostone, the aim is to spread that water across a wide area rather than send it all into one hole.^[2],[4]

A French drain along a wet foundation, set in Drain Rock or #57 Crushed Stone around a perforated pipe, can carry water to a storm drain, a rain garden or a broad, shallow stone bed. A splash bed of River Rock under each downspout slows the flow and spreads it out.^[1]

Permeable surfaces help too. Replacing a section of cracked concrete with #57 Crushed Stone over fabric lets some rain soak in where it lands instead of joining the runoff.^[1]

A rain garden suits carbonate ground. A shallow, wide basin with a layer of Drain Rock under Garden Soil and water-tolerant plants takes roof runoff in slowly across a large area instead of all at one point.^[1],[2]

Washed stone is the right choice for anything that sits wet. Drain Rock and #57 Crushed Stone leave open spaces between pieces, so water drains through before it can freeze and heave.^[4]

Beds and planters on city fill

Gardens on urban fill do best with imported soil. Raised beds and planters filled with Garden Soil keep roots above old debris. Topsoil spread over compacted ground helps a small lawn or a grass strip get started.^[1]

Mix Compost into beds each spring after the April 20 median last freeze at the airport station. A layer of Black Shredded Mulch or Brown Shredded Mulch holds moisture through summer and keeps soil from washing off sloped beds.^[4]

Beds on a slope hold soil better when terraced with low timber or stone edges. Each level stays flatter, takes water in more evenly and loses less mulch in a storm.^[1]

Mason Sand and Concrete Sand fill paver joints and bedding layers. Playground Sand fills a sandbox, and Wood Chips make a soft cover under a play set.^[1]

Housing in ZIP 18101

ZIP 18101 is in Lehigh County. The Census counts 2,786 housing units in the ZIP, and 4 percent are detached single-family houses.^[5]

The median home in ZIP 18101 was built in 1970, and owners live in 8 percent of the occupied units.^[5]

Allentown as a whole counts 49,502 housing units, with detached houses at 26 percent. The citywide median build year is 1952.^[5]

The ZIP's median build year is younger than the city's, which reflects the apartment blocks and newer buildings mixed among older rowhouses downtown.^[5]

With renters in most homes, outdoor work in the ZIP often falls to building owners and managers. Common jobs include topping up parking areas, refreshing stone strips along buildings and replacing mulch in shared beds.^[5]

PennDOT specifies Subbase, No. 2A aggregate, in Section 350 of Publication 408 Specifications (2026 Edition, Change No. 1).^[6]