#67 Stone for Tennessee Drain Beds, Pipe Runs and Concrete Work

Push a hand into a fresh pile of #67 stone and two things register before anything else. You can close a fist around a dozen pieces at once, and your glove comes away clean. Everything in the pile sits between a quarter inch and three quarters, every face is a fresh break with corners on it, and there is no dust film binding any of it together, because the material has been washed. That is a pile that will let water straight through and will never, under any amount of rolling, go hard.

A handful of #67 stone next to a handful of #57

Put the two piles side by side on a job and the difference is one step of size, which sounds trivial and is not.

#57 stone sits at roughly 3/16 inch up to an inch. The pieces are big enough to bridge across each other, so the voids between them are large and continuous, and the pile rattles when you walk on it.

This one runs a size down and carries the smaller fraction as well, so the pieces sit closer together. The voids are still open and still connected, they are simply narrower. That means it packs around a pipe or into a narrow trench far more neatly, and it reads as a tidier surface in a bed or a border somebody looks at every day.

Neither one has fines in it. Both drain. The smaller one is the one to reach for when the space is tight or the finish matters.

Tight trenches, small pipe and concrete that has to finish smooth

Three jobs account for most of the orders.

Drainage is the first: French drains, infiltration trenches and stormwater runs, where the stone surrounds a perforated pipe and holds an open route for water to reach it. The smaller size is useful around smaller diameter pipe, where inch stone bridges awkwardly and leaves gaps at the haunches.

Bedding and backfill around water, sewer and utility lines is the second, for the same reason. The material packs in around the barrel of the pipe, supports it evenly and lets water leave the trench instead of pooling in it.

The third is concrete, where a finer coarse aggregate makes a mix easier to place and finish. That matters on decorative work and countertops. Check the mix design before ordering, because aggregate size is specified by the pour.

When to step up to #57 or down to 3/8 inch chips

Going up a size, #57 stone is the standard choice for footing drains, wall backfill and free-draining parking pads, where the larger voids carry more water and the cost of a coarser surface does not matter.

Going down, 3/8" Crushed Stone suits shallow drainage and bedding where even this size is clumsy, and Drain Rock is worth a look for heavy French drain runs and the zone behind a retaining wall.

Going sideways to something that binds, Crusher Run is the material for anything that has to carry a tire.

Under a flagstone walk and between raised vegetable beds

Washed stone shows up on garden jobs for one reason: it moves water out from under things that would otherwise sit wet.

Under a flagstone walk on cherty clay, a layer of it gives rain somewhere to go instead of sitting between the clay and the underside of the stone, where it softens the bed and rocks the pieces loose. The flagstone itself still gets set on a thin course of fines, so this is the layer below that.

Between raised vegetable beds it does a plainer job. A gravel run between frames stays walkable after the beds have been watered and through a wet spring, where bare clay turns into a path of boot-clinging mud. It stays put better than bark and it will not need replacing each year.

A drainage blanket under a play frame, not the surface on top

This is where the size gets misordered, so it is worth being blunt about it.

Angular washed stone is a poor play surface. It is sharp, it is uncomfortable under a knee and it is the wrong thing to fall onto. What it does well under a play area is sit beneath the fall zone as a drainage blanket, taking the water that would otherwise leave the surface material soggy for a week after a storm. Put the rounded 3/8" Natural Pea Gravel on top for the surface people actually use.

How deep it goes, and what keeps cherty clay out of the voids

Depth follows the job. Around a perforated line, bed three to four inches under the pipe, cover it by six inches or so, and carry the stone up the trench so water can enter from the sides rather than only from the top. As a drainage layer under a walk or a play area, three to four inches over a compacted subgrade is a working figure. As a decorative ground cover, two inches is plenty.

What matters more than depth here is separation. On the cherty clay of the Highland Rim and the Central Basin, and in the silty ground out west, soil migrates into open stone under load and under repeated wetting. Once the voids fill, the layer stops draining and starts holding. Wrap the stone in a filter fabric, or lay fabric between the clay and the stone on a blanket application, and the layer keeps working instead of silting up from the inside.

Yards and tons for the walk, the beds and the play area

Three hypothetical examples, worked the way this site's calculator works: length times width times depth in inches, divided by twelve, divided by twenty seven, then multiplied by weight. Washed crushed stone in this family runs about 2,800 lb per cubic yard on this site's published figures, near enough 1.4 tons per cubic yard.

A drainage layer under a flagstone walk, 36 feet by 3.5 feet at four inches. 126 square feet. 126 x 4 = 504, divided by 12 = 42 cubic feet. Divided by 27 = 1.6 cubic yards, about 2.2 tons.

A gravel run between raised vegetable beds, 18 feet by 12 feet at three inches. 216 square feet. 216 x 3 = 648, divided by 12 = 54 cubic feet. Divided by 27 = 2 cubic yards, about 2.8 tons.

A drainage blanket under a play frame, 20 feet by 16 feet at three inches. 320 square feet. 320 x 3 = 960, divided by 12 = 80 cubic feet. Divided by 27 = 3 cubic yards, about 4.1 tons.

Put your own measurements through the stone calculator, which will convert to tons and let you add a margin for trench walls that always take more than the drawing said.

Setting a quantity while the trench is still open

An open trench in this climate is a trench waiting on the next storm, so order to land the week the work happens rather than two weeks ahead. A pile of washed stone will sit through a rain event without turning to sludge, though on a grade it creeps, so a drop spot on a slope wants a board or a bucket to check it. Delivery is arranged at checkout by ZIP code and the truck needs clear access to a place it can tip, which the delivery page explains. Measure, work the yardage, then choose an amount and a date on this page. If the drain crosses a ditch, a culvert or a property line and you would rather talk it over first, use contact.