#4 Crushed Stone: The 3/4 to 1-1/2 Inch Size for Soft Ground

Some ground eats gravel. A farm track across low, wet bottom land, a bank below a culvert that washes out every spring, a yard on soft river silt where every load of drive stone quietly vanishes into the mud within two seasons: these are the situations that bring people to #4 crushed stone, and they occur in every region of the country for different reasons. In the northern tier it is the spring thaw that turns a firm track to soup. Along the gulf and the southeast it is rainfall volume. On the high plains it is a dry wash that runs hard for two hours a year.

Pick a piece up and the difference is obvious. It fills a hand, it has broken faces and sharp edges, and it is heavy enough that you place it rather than shovel it in quantity. The size runs roughly 3/4 inch to 1-1/2 inches, and a pile of it has caves in it: the gaps between pieces are large enough to see through.

Ground that swallows smaller stone is where #4 crushed stone belongs

Those big voids and that weight are the whole argument for the material.

• Heavy-duty base under a drive or work area. Placed as the lower course on soft subgrade, the stone bridges over ground that will not carry a load, with a finer material above it to fill the surface.
• Erosion control on slopes, ditches and channels. Angular pieces this heavy interlock and stay put in flows that would carry a drive stone away.
• High-volume drainage. Where a lot of water has to move fast, the open structure moves it.
• Gabion fill. The size sits well inside basket mesh without falling through it.

Wrong pick under a flagstone walk, and wrong pick in a raised bed

Two jobs come up on this page that call for something else.

A flagstone walkway needs a flat, true bed. Stone this size cannot be screeded level and would rock every slab set on it. Build the walk on a compacted base of Crusher Run with a thin bedding course of Stone Screenings on top, and keep the large stone for whatever soft ground sits beneath all of it.

Raised vegetable beds are the other one. A thin drainage layer of coarse stone in the bottom of a bed does less than people think, and at this size it takes up growing depth and makes the bed awkward to ever dismantle. Beds want Garden Soil, with the drainage handled by what the bed sits on rather than by rock inside it.

Depth under a single-car track, and thickness along a washout

Depth here is about bridging, not about surfacing.

• Bridging soft subgrade under a drive: 6 to 8 inches of the large stone as a lower course, laid over a separation fabric, then a finer compacted layer on top of it. On genuinely boggy ground, more depth is the crude fix and better drainage is the real one.
• A ditch or a washed bank: 8 to 12 inches, bedded so the stone keys into the slope rather than resting on it. Where flow is strong enough to move this size, step up to RipRap instead.
• Behind a structure or in a basket: fill to the dimension of the void, and expect to place the pieces by hand for a tidy face.

Never finish a drive with this size. It is uncomfortable to walk on, it throws pieces under tires and nothing binds it together.

Cubic yards for a 60 foot track and a run of gabion baskets

Both examples are hypothetical. This site's calculator figures #4 stone at about 2,900 lb per cubic yard, or 1.45 tons per yard, so the tonnages below are approximate; the stone calculator will run the same conversion on your own dimensions.

Bridging course under a track. 60 feet long by 10 feet wide at 6 inches: 60 x 10 = 600 square feet. 600 x 6 / 12 = 300 cubic feet. 300 / 27 = 11.11 cubic yards. At 1.45 tons per yard that is 11.11 x 1.45 = roughly 16.1 tons.

Gabion run. Five baskets, each 3 by 3 by 3 feet: 3 x 3 x 3 = 27 cubic feet per basket, which is 1 cubic yard each, so 5 cubic yards for the run, and 5 x 1.45 = approximately 7.3 tons. Order a little over, because a hand-placed face uses more than the arithmetic suggests.

At this size, coverage is shallow: one cubic yard spread 6 inches deep covers about 54 square feet, and at 8 inches about 40 square feet.

The size either side, and when to step across

Getting a heavy load to the part of the yard that needs it

Set the tonnage and the delivery date together on this page; delivery is arranged at checkout by ZIP code. Plan the drop carefully with a material this heavy. Move it with a tractor bucket or a skid steer if you can, because wheelbarrow work at this size is slow and hard on both hands and grass. Ask for the load on firm ground with clear overhead room, close to the ditch, track or basket run it is destined for. For a slope or a channel you are unsure about, send the dimensions through the contact page and request a quote by email.