#67 Stone for Trenches Cut Through Till and Ledge

Digging here is rarely a clean job. The bar hits a boulder at two feet, ledge at three, and what comes out of the hole is a mix of till, roots and stone that will never backfill evenly. #67 stone is what goes back in when the trench has to work regardless of what came out of it.

Size is 1/4 inch to 3/4 inch, graded to the #67 band, angular crushed rock with the fines washed out.

The gaps between the pieces are the product. Everything below follows from that.

Order it when water has to keep moving through the layer

Reach for this size where the layer's job is to stay open.

• Bedding and surround for a water, sewer or utility line, working into the haunches under the pipe.
• Infiltration trenches and dry wells taking roof or yard runoff.
• Behind a wall or along a foundation, giving water a route out.
• As concrete aggregate where the finish is going to be seen.
• As a visible cover in beds, tree rings and borders.

The even grading is what keeps silt from choking it. Mixed sizes leave small gaps that fines bridge and seal. A narrow band leaves gaps of one rough size, and water keeps finding a way through.

Two jobs it will let you down on: a new lawn and a camp road

New lawn ground is not stone work. Grass wants a rooting depth of screened loam, and a clean crushed layer under seed dries out fast and gives roots nothing to hold.

A camp road is the other one. Clean stone with no fines will not knit together. It migrates to the shoulders under tires, it refuses to hold a crown, and it rolls underfoot. A lane wants the structural depth of crushed gravel with a surfacing course over it.

Put another way: this material carries water, not traffic.

Bedding a utility line, and the beds where the stone stays visible

In a trench, the stone goes in below the pipe as well as around it. Four inches of bedding under the line, worked in along both sides so the pipe is supported at the haunches rather than resting on two points, then cover over the top before any backfill.

Line the whole envelope with geotextile. Till and silt migrate into open stone from every side, and a trench that drained beautifully in June can be silted up within a few seasons without fabric.

Above ground the same material reads differently. The angular faces and the narrow size band give a bed a deliberate, even look, and it does not break down into the planting the way bark does. It also reflects heat back at anything growing in it, so keep it clear of the crowns of plants that mind that.

Why #67 stone sits above a base and never becomes one

A compacted layer needs fines to fill the gaps and lock the stone. This one has had those washed out.

Run a plate compactor over it and the pieces shuffle, seat a little, and stop. That is as dense as it gets, and it is dense enough to hold a spa or a shed but not to behave like a road base.

The other half of the picture is frost. Water sitting in a tight layer expands when it freezes and lifts whatever is above it. An open layer gives that water somewhere to go before it turns to ice, which is why clean stone shows up under pads and behind walls in a state where frost reaches four feet.

Working out a 10 by 10 spa base and a 4 by 28 run beside the house

Two hypothetical jobs, plus one that is not a stone job at all. This size runs about 2,800 lb per cubic yard on this site's published figures, near enough to 1.40 tons per yard.

Hot tub base, 10 ft by 10 ft, 6 inches deep

• 10 x 10 = 100 sq ft
• 100 x 6 / 12 = 50 cu ft
• 50 / 27 = 1.85 cu yd
• 1.85 x 1.40 = 2.6 tons, order 3

Side-yard dog run, 4 ft by 28 ft, 3 inches over fabric

• 4 x 28 = 112 sq ft
• 112 x 3 / 12 = 28 cu ft
• 28 / 27 = 1.04 cu yd
• 1.04 x 1.40 = 1.5 tons

New lawn strip, 900 sq ft at 4 inches

• 900 x 4 / 12 = 300 cu ft
• 300 / 27 = 11.1 cu yd of loam, not stone

Round up on the first two. Stone spread over an uneven subgrade always takes more than the arithmetic says, and the surplus goes round the downspouts. The stone calculator will run other shapes.

Picking a drop spot for a load that rolls

Set quantity and delivery date here. Delivery is arranged at checkout by ZIP code.

Washed stone spreads wider when it lands than a base material does, so allow more room than the pile looks like it needs. Firm ground, room to back, clear height to raise the body.

If the trench is already open, keep the drop well clear of the edge. Stone rolling into an open trench before the pipe and fabric are in costs an afternoon.

Working from a drawing that names a grade? Check it against the product list before you order, or ask through the contact page.