CR-6 in Maryland: Base Stone for Drives, Pads and Paver Work

Most CR-6 orders start with a decision that is already half made. A lane has begun to rut after a wet spring, or a paver patio is going in, and the question is no longer whether the job needs a compacted base but which of three similar looking blends belongs under it. That choice carries further here than it looks, because a Howard County lot on silt loam over hard crystalline rock and a Dorchester County lot on flat Coastal Plain sand fail in completely different ways when the base underneath is wrong.

CR-6 is the name Maryland yards put on the dense-graded blend that goes beneath driveways, parking pads, shed floors and pavers. MDOT SHA Section 901 is where aggregates get specified for road work in this state, and graded aggregate base is the highway term; CR-6 is what the same material is called when it arrives on a residential job.

CR-6, Crusher Run and stone dust in the same wheelbarrow

These three get ordered interchangeably and should not be. They are separate products with separate jobs.

The fines are the whole point of CR-6. Crushed stone, gravel and dust in a graded range means the small particles fill the gaps between the large ones, and once the layer is damp and compacted it behaves as one dense mass rather than a heap of loose rock.

Ground from Garrett County to the Eastern Shore, and what each asks of the base

• On Central Maryland Piedmont loam and silt loam, the subgrade turns soft when saturated and stays that way for days. The base has to be thick enough to bridge it, and the surface above needs a crown so storm runoff leaves rather than soaks in.
• In the limestone valleys around Hagerstown and Frederick, water drains down through cracks in the rock. Spread drive and downspout water out rather than funneling it to one spot, and check low areas for new depressions after heavy spring rain before you lay base over them.
• On Western Shore and Eastern Shore Coastal Plain ground, the subgrade is unconsolidated sand, silt and clay rather than weathered rock. Well drained sandy loam on high ground takes base readily; low, flat sites near tidal water hold water and need the base built up above the wet.
• In Garrett and Allegany counties the frost line runs to 36 inches and winters are the longest in the state, so a thin base gets heaved and then softens at the thaw.
• Across most of Maryland the code frost depth is around 30 inches, dropping to 24 in several Eastern Shore counties. A residential drive is not founded below frost, which is exactly why the base has to drain rather than hold water through a freeze.

Within 1,000 feet of tidal water, Critical Area rules limit how much of a lot can be covered, and gravel and stone surfaces count toward that figure. Confirm your allowance before you widen a drive or add a pad.

Measuring a 320-foot lane outside Westminster

The arithmetic is length times width times depth in feet, divided by 27 for cubic yards. Depth in inches divides by 12 first.

• Example, a long rural lane, 320 feet by 10 feet at 6 inches compacted: 320 x 10 = 3,200 square feet. 6 inches is 0.5 feet, so 3,200 x 0.5 = 1,600 cubic feet. 1,600 divided by 27 = 59.3 cubic yards.
• Add for compaction. A loose layer settles as it is rolled, so order against the finished depth you want rather than the pile height, and take the extra rather than run 20 feet short at the far end.
• Example, the same lane built in two lifts of 3 inches each rather than one 6 inch pass: the total is identical at 59.3 cubic yards, but each lift compacts properly instead of leaving a soft middle.

At this site's published weight for the crusher run and road base family, about 1.50 tons per cubic yard and approximate, 59.3 cubic yards of CR-6 is roughly 89 tons. Put those cubic yards into the CR-6 calculator to check the tonnage before you order.

A garden path and a new lawn: two jobs that want something else

• Example, a garden path 40 feet by 3 feet. That is 120 square feet, and at 2 inches it comes to 120 x 0.1667 = 20 cubic feet, or 0.74 cubic yards. The yardage is easy. The material is wrong. Fines track indoors on shoe soles and turn greasy in a summer downpour, so use Walkway Gravel for the walking surface and keep CR-6 for the compacted layer underneath if the path crosses soft ground.
• Example, new lawn prep over 1,500 square feet. CR-6 has no place here at all. Shape the grade, then finish with Top Soil at the depth the seed or sod needs. A base blend under a lawn produces a strip that never grows in.
• The dividing line is simple. CR-6 goes where something has to carry weight or stay dimensionally stable. It does not go where roots grow or where bare feet land.

Setting a quantity and a date once the lane is measured

Delivery is arranged at checkout from your ZIP code, so the useful preparation is on your side of the fence. Pick a dump spot the truck can reach and reverse out of, with clear overhead room and firm ground under the wheels, and mark it before the day. Aggregate goes down easiest on ground that has already been shaped, so cut the grade, sort the drainage and stake the edges first.

Work out your depth, run the numbers through the calculator, then choose a tonnage and a date on this page. If the lane is long or the access is tight, send the measurements and a photo through contact and the quantity can be talked through before you book anything.