Washed Rock in Montana
Also sold as Drain Rock
Also known as: 3/4 clean, drain rock
Washed Rock belongs in Montana drainage fill behind retaining walls and in trench work, keeping a clear route for water rather than holding it against the structure.
- Size: 3/4 inch to 1-1/2 inch
- Grading: Washed to remove fines and dust
- Type: Rounded or angular varieties
From $383.00 for 1 ton, delivery included
Larger loads cost less per ton: 500 tons is $23,095.00 ($46.19 per ton). Pick any quantity below for a delivered price.
Free delivery included
Free delivery anywhere in Montana
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Weekday delivery, earliest Sep 25
“Grabbed three tons of drain rock for a dry well at the bottom of our downspout run near Augusta. Water disappears into it within minutes now instead of pooling by the foundation. Clean stone with hardly any fines mixed in, unlike the pit run we tried first.”
Earl V. · Verified Buyer
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Everything You Need to Know About Washed Rock
Size and Grading
- Size
- 3/4 inch to 1-1/2 inch
- Grading
- Washed to remove fines and dust
- Type
- Rounded or angular varieties
Wall excavation and trench drainage are places where Montana contractors need Washed Rock to remain open after surrounding material is placed. This clean, washed aggregate has no fines or dust filling the gaps among its pieces. It gives collected water a route through retaining-wall backfill, septic field areas, and French drains.
Deep frost and repeated freeze-thaw cycles make it important to keep Montana drainage zones distinct from surrounding fill. Across the Yellowstone River country and the Gallatin Valley, clay can hold moisture close to wall work. Select angular Washed Rock where backfill bears against the drainage layer, since its shape helps preserve the open arrangement under weight. That helps collected water leave the area instead of remaining beside the structure. Rounded material is a practical choice for a visible drain detail that calls for a natural stone look. It can also remain visible after the work is complete.
Quickly Calculate How Much You Need
Material: Washed Rock
How to Measure
Measure the length and width of your project area in feet
Decide on depth in inches (2" for landscaping, 4" for driveways)
Enter the values above and we'll calculate the tonnage you need
Need help figuring out the right amount? We can help!
Call or text us at our contact form and we'll help you calculate the right quantity for your project.
Not sure how much you need? The River Rock Calculator has depth guides, coverage charts and worked examples for this material.
Common Uses
French Drain Systems
French drains need open aggregate so water can move through the trench. Drain rock carries water away from footings, below-grade walls, and low ground, helping limit water-related problems around a property.
Septic & Leach Field Construction
Septic wastewater needs a permeable rock bed for infiltration. Drain rock is used beneath and around septic dispersal areas, including leach fields, where applicable health department requirements govern the installation.
Retaining Wall Backfill
Water trapped behind a retaining wall builds pressure against it. Placing drain rock in the backfill gives that water a path out, reducing pressure that can affect the wall.
Foundation Drainage
Groundwater at a foundation can reach walls and footings if it has nowhere to go. Set drain rock around the perimeter to move water toward the drain line and reduce moisture and pressure at the structure.
Why Choose Washed Rock
Maximum Water Flow
Because fines and dust are removed, drain rock leaves open spaces between the pieces. Those voids let water pass through the drainage layer without being blocked by small material.
Long-Term Performance
Angular rock pieces interlock while retaining openings under load. Compared with rounded aggregate, this helps the drainage layer resist settlement and compaction that can restrict water movement.
Clean & Specification-Grade
Washed, graded drain rock is suited to drainage assemblies using fabric, perforated pipe, and related components. Check the project requirements for the required gradation.
Structural Protection
Water near foundations, walls, and other structures can create moisture concerns and pressure in the surrounding soil. A drain rock layer provides a route for that water to leave the area.
Frequently Asked Questions About Washed Rock
Customer Reviews
Barn drain keeps the ground firm
Used five tons for a French drain along the low side of the barn out past Power. Water used to stand there every spring and soften the ground under the equipment. Ordered through Montana Rock Supply and the driver dumped it right along the trench line where we marked it, draining fast now even after a hard rain.
Faith W. · Power, MT · Verified Buyer
Retaining wall stayed dry through fall
We built a retaining wall for a client in the Mission Valley near St. Ignatius and needed clean drain rock behind it so pressure wouldn't build up once the fall rains started. Fourteen tons went in behind the wall and around the weep holes, tamped in lifts as the wall went up course by course. Through a wet fall and a heavy spring melt off the mountains the wall hasn't budged an inch and there's no standing water anywhere near the base. Montana Rock Supply had the washed stone ready the same week we needed it, no waiting on a special order.
Denise X. · St. Ignatius, MT · Verified Buyer
Entrance drain works, dustier than hoped
Six tons of drain rock for a drainage run along our entrance sign near Valier. Works well and looks tidy from the road. Only complaint is the load ran a bit dustier than the washed stone we were expecting based on the description.
Glen T. · Valier, MT · Verified Buyer
Downspout puddle finally gone
Grabbed three tons of drain rock for a dry well at the bottom of our downspout run near Augusta. Water disappears into it within minutes now instead of pooling by the foundation. Clean stone with hardly any fines mixed in, unlike the pit run we tried first.
Earl V. · Augusta, MT · Verified Buyer
Washed Rock has 4 verified customer reviews with an average rating of 4.8 out of 5.
