#67 Stone in Pennsylvania: Clean 1/4 to 3/4 Inch Crushed Rock

In the glaciated northwest, a trench tells you about the ground faster than any soil map. Dig two feet into stony till on an upland lot in April and the sidewalls start weeping, because there is a dense, slow-draining layer not far below the surface and water sits perched above it from fall until late spring. That is the ground most orders of #67 stone go into, and it is why the material leaving the yard for that corner of the state goes out under a trench line more often than anywhere else.

Bedding pipe and utility line where water sits above the till

Pipe bedding is the job. A water line, a sewer lateral, a downspout run or a conduit needs continuous, even support along its length, and it needs the trench to keep draining once the ground around it is wet. Clean angular stone at this size does both. It beds down around the haunches of a pipe without leaving voids, it does not settle unevenly the way loose soil backfill does, and water moving along the trench has somewhere to go rather than standing against the line.

The smaller top end of the gradation is the reason it is preferred over coarser stone for this work. The pieces pack closer around a pipe, so the bedding contacts the line rather than bridging across it on three sharp points.

Quarter inch to three quarters, graded to the #67 band

What is in the pile is angular crushed rock, washed clean of fines, with the pieces running from a quarter of an inch up to three quarters. Everything is roughly the same order of size, which is what makes the layer both uniform to look at and open enough for water to move through.

Two neighboring listings cause most of the ordering mistakes. #57 Stone is the next band up, running to about an inch, and the name Pennsylvania yards traditionally use for that size is 2B, sold here as 2B Stone. Below this one sits the small clean chip, 1B in the older local naming, listed as #8 Crushed Stone. PennDOT Publication 408, Section 703 sizes clean stone by AASHTO number, which is where #67 comes from, and the older size names have stayed in trade use alongside the numbers. Order to whichever name your spec sheet or your contractor gave you.

Beds, pads and roof water: which of the three takes #67 stone

• A dry landscape or rock garden bed. Yes, and it is a tidier cover than larger stone, because the uniform smaller pieces read as a deliberate finish around plantings and tree rings. Put fabric under it on till ground or silt will work up into it.
• A shed or garage pad base. Only as the drainage layer. Clean stone will not compact into structure, so the load-carrying course beneath a pad is 2A Modified, with this stone used under it or as the capillary break under a slab.
• A downspout run and splash zone. Yes, and this is where the size earns itself. Roof water arrives concentrated and fast, and an open stone bed takes it away from the wall instead of letting it soak in beside the footing.

Perched water, and what a wet April does to an open trench

Water above a dense till layer does not drain downwards, it moves sideways until something intercepts it. A stone-filled trench is an interception, whether you meant it to be one or not. That works in your favor on a French drain and against you if a bedding trench runs downhill towards a foundation without a plan for where the water comes out.

Two practical consequences. First, wrap drainage and bedding trenches in a permeable geotextile, top and sides, because silt entering the voids from wet till is what fills a trench in and stops it working. Second, know the outlet before you dig. A trench with nowhere to daylight is a reservoir with stone in it.

Frost through this zone commonly reaches 36 inches or more, set by each municipality, so service lines are buried well below the depth being discussed here; the bedding stone is doing drainage and support work, not frost protection.

How deep it goes, and whether that figure is loose or tamped

Bedding thickness under a pipe is normally a matter of inches beneath the barrel and enough material over the top to protect the line before the soil backfill goes on, and the numbers come from the utility or the plumber rather than from a stone yard. What a stone order needs is volume, so measure the trench and fill it on paper.

For an area rather than a trench, the calculator's own depth guide puts landscaping work at about 2 inches and driveway work at about 4. Treat those as loose spread depths. Clean stone does not compact into a thinner layer the way a dense-graded base does, since there are no fines to fill the voids, so it settles and locks rather than shrinking. Order to the loose depth and you will not be short.

Tonnage for 48 feet of trench and a 12 by 20 garage pad

All examples are hypothetical. Cubic feet divided by 27 gives cubic yards. This site publishes #67 and other clean stone in the three-quarter family at about 2,800 lb per cubic yard, which works out at 1.40 tons per yard.

The pipe itself displaces a little of the trench volume, though on a small-diameter line the difference is inside the rounding and not worth deducting. For anything with corners or curves in it, the stone calculator will take up to five areas at once and carries the same weight figures.

Picking a drop spot a loader can reach behind the garage

Clean stone is the easiest material on this site to move by hand and one of the worst to move twice, so put the pile where the work is. Once quantity and delivery date are chosen on this page, delivery is set at checkout from your ZIP code, and the driver needs firm ground to dump on with clearance above and room to back out. On till ground in spring, firm is doing a lot of work in that sentence, so check the route before the date rather than on the day. Anything tight about the approach goes to Contact first.