#67 Stone in Tight Virginia Trenches and Finished Concrete

The order that most often needs correcting is a trench dug for a small perforated line and backfilled with stone too coarse to pack around it. The pipe sits on points instead of on support, the larger pieces bridge over voids, and a year of Piedmont runoff washes silt into the gaps that were never meant to be there. #67 stone is the size people come back for once that has happened, and it is worth choosing deliberately the first time rather than by correction.

Where #67 stone earns its place on a Virginia job, and where it does not

Size here is 1/4 inch to 3/4 inch, graded to the #67 designation, angular crushed stone. Locally the number comes from the VDOT washed stone sizes, which is how yards and drawings across the state describe material rather than a certification this storefront holds.

Take it when:

• The space is tight. A narrow trench, the haunch area around a small pipe, or a shallow backfill where a coarser stone will not pack down properly.
• The concrete has to finish smooth. A smaller aggregate leaves a surface that trowels and polishes better, which matters where the slab stays visible.
• A bed or a tree ring wants an even, uniform look rather than a mix of visibly different sizes.
• Water has to move through the layer at a steady rate without the voids being wide enough to swallow fine soil.

Leave it when:

• The layer has to carry weight and stay put. Washed stone has no fines in it, so it never locks up. A dense-graded base such as 21A is what carries.
• You want a compacted, walkable finish. That is a job for Screenings over a base.
• The flow is heavy enough to move the stone, at a culvert outlet or on a scoured bank, where a much larger rock belongs.

Around a perforated line, under a barn slab, and in the mix itself

The pipe surround is the job it does best. Bed the line on a layer of stone, bring the backfill up evenly on both sides so the pipe is supported at the haunches, and cover it before anything heavier goes on top. The smaller size packs around a 4 inch line without leaving the large voids a coarser stone leaves.

Under a slab or a barn floor it works as the free-draining layer that breaks the connection between wet ground and the concrete above it, particularly on slow-draining clay where moisture would otherwise sit against the underside. It is that layer, not the structural one, and a compacted base still goes in first.

As concrete aggregate it suits mixes where the finished surface stays on show. That is the one use on this list where the number on the drawing is not negotiable: order the size the mix design calls for.

What goes under it on coastal ground and on clay

Open stone dropped onto soft ground is pushed into it, and the layer thins from the bottom without anyone seeing it happen.

• On flat Coastal Plain ground through Hampton Roads, the Eastern Shore and the river necks, water sits close to the surface and fine sand and silt move easily. Separate the stone from the subgrade and keep the finished grade shedding water away, since there is nowhere for it to go sideways.
• On Piedmont clay the stone holds up for a season and then sinks in the loaded spots. A compacted base under it, and separation between the clay and the voids, keeps both layers doing their own work.
• In the limestone valleys west of the Blue Ridge, rock often sits close to the surface. The layer is shallower there, and the question becomes where the concentrated flow leaves, since runoff funneled into karst ground goes down into the rock.

Freeze and thaw works on any layer that holds water, which is another argument for keeping the voids open and the silt out.

An L-shaped pad, a short drive and a garden walk: the arithmetic

Length in feet by width in feet, times depth in inches divided by 12, divided by 27 gives cubic yards. This site publishes roughly 2,800 lb per cubic yard for washed stone in the #57, #67 and 3/4 inch family, about 1.40 tons per yard. Treat that weight as approximate.

• Example, an L-shaped pole barn and equipment pad. Split it into rectangles: a 30 ft by 40 ft main area is 1,200 sq ft, the 12 ft by 16 ft apron is 192 sq ft, total 1,392 sq ft. At 6 inches, 1,392 x 0.5 = 696 cubic feet. 696 / 27 = 25.8 cubic yards, roughly 36 tons.
• Example, a single-car gravel driveway 9 ft by 70 ft topped at 2 inches: 630 sq ft x 0.167 = 105 cubic feet. 105 / 27 = 3.9 cubic yards, roughly 5.4 tons.
• Example, a flagstone walkway 3.5 ft wide and 26 ft long with a 4 inch drainage layer beneath the setting bed: 91 sq ft x 0.333 = 30.3 cubic feet. 30.3 / 27 = 1.1 cubic yards, roughly 1.6 tons.

These are illustrations rather than jobs that were built. Because the material is open graded it does not tighten down much once placed, so the depth you spread is close to the depth you keep. Put your own measurements through the stone calculator, then set a quantity and a delivery date on this page. Delivery is arranged at checkout from your ZIP code, so choose a tipping spot a loaded truck can reach before you book.