Class 6 Road Base vs Pit Run vs Structure Fill: Which Do You Need?
By Seth Cvancara, Founder, Mouse Mining LLC. Updated .
Class 6 road base is a crushed, graded aggregate that compacts into a firm base for driveways, roads and slabs. Pit run is unprocessed material used for bulk fill. Structure fill is a controlled fill placed around foundations and structures where plans call for it. Mouse Mining matches whichever your plans specify.
These three products get mixed up on job sites all the time, and the wrong one can fail inspection. This post is part of our guide to ordering bulk rock and aggregate.
What is the difference between road base, pit run and structure fill?
The difference is processing and purpose. Road base is crushed and graded to compact tight under load. Pit run comes out of the pit largely as is and is used where volume matters more than gradation. Structure fill is specified by the engineer for fill around and under structures.
| Class 6 road base | Pit run | Structure fill | |
|---|---|---|---|
| What it is | Crushed, graded aggregate | Unprocessed pit material | Engineer specified fill |
| Typical use | Driveways, roads, under slabs | Bulk fill, grade raises, sub base | Around foundations and structures |
| Compacts to | Firm, load bearing surface | Varies with the pit | Per project spec |
| Best for | Anything that carries traffic | Moving volume economically | Meeting a structural spec |
When should I use Class 6 road base?
Use Class 6 road base anywhere the surface has to carry vehicles or support a slab: driveways, parking areas, access roads and base under concrete or pavers. It is the common Colorado base course callout. Place it in lifts and compact each one.
See Class 6 road base for availability, and calculate how many tons you need.
When is pit run the right choice?
Pit run fits jobs where you need a lot of material to raise grade or fill a void and gradation is not tightly specified. It is often used as sub base below a road base layer. Because it comes from the pit largely unprocessed, what you get depends on the source.
Details on pit run fill.
When do plans call for structure fill?
Structure fill shows up on plans for backfill around foundations, retaining walls, utility structures and under footings, where the engineer needs a controlled material. Order it by the spec on the plan sheet, not by name alone, since what one pit calls structure fill may differ from another.
Details on structure fill. Send the spec with your quote request and we will match it or confirm an equivalent.
How do I make sure I order the right one?
Order from the spec callout on your plans, not the trade name. Specs and local names vary from pit to pit. Send Mouse Mining the plan sheet or spec, and we identify the material, source it from the closest contracted pit and confirm any equivalent before it ships.
Then see what a delivered price covers.
Need a delivered price?
Send the material, tonnage and delivery location. 25 ton minimum. Delivering across Colorado, Wyoming, New Mexico, Utah, Arizona and Texas.
Frequently asked questions
Is Class 6 the same as road base?
Class 6 is the common Colorado callout for road base course. Confirm the spec on your plans, since requirements vary by project.
Can I use pit run instead of road base on a driveway?
Pit run is usually used as sub base or bulk fill. Driveway surfaces and slab bases typically call for a graded road base that compacts tight.
Does Mouse Mining deliver road base outside Colorado?
Base and fill products are featured on our Colorado, Wyoming, New Mexico and Utah city pages. Call to confirm availability for your location.
What is the minimum order for road base?
Full truckloads with a 25 ton minimum.
Can you match the spec on my plans?
Yes. Send the spec callout and we will match it or confirm an equivalent before delivery.