Breaker Run Stone: What It Is, Sizes and Subgrade Uses

Breaker run is the heavy-duty stone used when the ground is too soft to build on. It is rock (or old concrete) that has been through a primary crusher one time and nothing more: no screening, no second crusher. The result is a jumble of angular pieces, many of them several inches across, plus the smaller bits and dust that came off during crushing. Crews dump it into soft subgrade, roll it, and get a firm platform for the road base above. The term is common in Wisconsin and the upper Midwest, where the state DOT has a standard spec for it. This guide covers what it is, how it is placed and how to figure tons.

Crushed stone calculator →

Quick facts

Source: quarry stone or broken concrete run once through a primary crusher.
Size: Wisconsin DOT section 311 wants mostly pieces of 6 inches or under in one direction or more, with no extra screening or crushing.
Job: subgrade correction and improvement, meaning bridging soft, wet or pumping soil.
Layering: the same spec places and compacts it in layers of 16 inches or less, with thicker lifts allowed for very soft foundations.
Weight for pay: the spec converts volume to weight at 1.75 tons per cubic yard of in-place material.

How breaker run fixes soft ground

Soft clay or saturated silt cannot carry a truck without rutting, and it will swallow small stone. Breaker run works because the pieces are big and angular. When they are dumped and rolled, they press into the top of the soft soil and wedge against each other, creating a stiff, interlocked layer. That layer spreads loads so the next layer, usually a crushed base with a controlled gradation, can be compacted properly. Because the voids between big stones are large, a finer layer or a separation fabric is often used so the base above does not sift down into it.

What the spec allows

Wisconsin DOT's standard spec gives a good picture of what a quality product looks like:

It should come from an approved quarry with acceptable wear and soundness test results on record.
It should be largely free of overburden, topsoil, organic matter, steel and other junk.
Crushed concrete can qualify if it is mostly free of steel and building debris.
The engineer can reject material made from deteriorated concrete or weak rock such as sandstone, shale, slate or heavily weathered granite.
Acceptance is based mainly on the engineer's visual inspection, since a 6-inch product does not lend itself to small lab samples.

If you are buying for a private driveway, use those same points as a checklist: hard rock, few fines, no trash.

Breaker run vs similar stone

Material	How it is made	Typical use
Breaker run	One pass through a primary crusher, unscreened	Soft subgrade bridging
Shot rock	Blasted rock, often not crushed at all	Bulk fill, very soft ground
Riprap	Graded armor stone	Erosion protection on slopes and channels
Crushed base (crusher run, road base)	Crushed and screened to a gradation	Compacted base right under the pavement or surface stone

Using breaker run on a driveway

Homeowners usually meet breaker run when a driveway or pole-barn approach keeps rutting no matter how much gravel goes on. The common sequence is:

Dig out the soft, wet soil to firmer ground or to the depth your contractor recommends. Our undercutting guide explains why.
Fix the water first: ditches, a culvert or a drain so the hole does not refill.
Dump breaker run, spread it with a dozer or skid steer and track or roll it in.
Choke the surface with a finer stone or lay fabric, then build a crushed base in compacted lifts.
Finish with a surface stone or pave. See the base calculator for the upper layers.

Freeze-thaw areas see this most often in spring; our spring thaw guide covers the symptoms.

How much breaker run do you need?

Here is a made-up example using the Wisconsin DOT in-place factor:

Soft section: 14 feet wide, 40 feet long, dug out 12 inches deep.
Volume: 14 × 40 × 1 = 560 cubic feet, or about 20.7 cubic yards.
At 1.75 tons per in-place cubic yard: about 36 tons.

Very soft ground can swallow more stone than the hole size suggests, so ask the quarry about returns or keep a spare load in mind. The crushed stone calculator lets you plug in your own dimensions and density, and tons per dump truck helps you plan deliveries.

Questions people ask

What is breaker run stone?

It is rock or concrete that has gone through a primary crusher once and has not been screened or crushed further. Under Wisconsin DOT's spec, most pieces must measure 6 inches or under in one direction or more, and its main job is to correct and improve subgrade.

What is breaker run used for?

Mostly for stabilizing soft or wet ground under roads, parking lots, building pads and long driveways. The big angular pieces push into the soft soil and lock together, giving a working platform that later layers of finer crushed base can be built on.

How thick is a breaker run layer?

That depends on how soft the ground is and is set by the plans or an engineer. Wisconsin DOT's spec has contractors place and compact it in layers of 16 inches or less, with thicker layers allowed when the foundation is very soft.

How much does breaker run weigh per cubic yard?

Wisconsin DOT uses a conversion factor of 1.75 tons per cubic yard for in-place, compacted breaker run when it converts volume to weight for payment. A supplier's loose weight will differ, so ask for their number when ordering.

Can you drive on breaker run?

Trucks and equipment can run on it during construction, but it is far too coarse to be a finished driveway. It needs a cap of crushed base and then a surface stone or pavement.

Is breaker run the same as riprap?

No. Riprap is graded armor stone, sized and placed to resist moving water on slopes and channels. Breaker run is an unscreened crusher product used inside the pavement structure to bridge soft soil.

As an Amazon Associate, AsphaltTons.com earns from qualifying purchases. Product links below are sponsored.