2 1/2 Inch Base Course Gravel for Fill and Base Layers

Also known as 2 1/2 Inch Select Borrow or 2 1/2 minus, this material runs from 2 1/2 inch rock down to fines in a graded blend built to compact. The combination of mid-sized rock and fine material is what lets it lock together into a firm, load-bearing base, which makes it useful as both a fill and a structured base layer in spots where 6 Inch Minus runs too large to finish cleanly.

In practice it most often serves as a middle layer under house pads, driveways, and parking areas. It is commonly placed over a coarser lift such as 6 Inch Minus, then topped with a finer 1 1/2 inch or 3/4 inch course to reach final grade. Laid in lifts and compacted, the fines drive into the gaps between the rock and bind the layer so it holds its shape under load.

Think of 2 1/2 Inch Base Course as the step between rough fill and a finished base. It is too coarse to be a final wear surface on its own, but it builds depth and stability faster than the finer courses, so using it in the right layer saves both material and time. If you are unsure how deep to run it or what to cap it with, your contractor can size the layers to the job.

Common uses:

• Compacted base under pads, driveways, and parking
• Middle layer over 6 inch minus
• Structured fill where a finer grade is needed
• Building depth before a finer top course
• Leveling areas that need a firm base

Good to know:

• Also called 2 1/2 Select Borrow or 2 1/2 minus
• Graded from 2 1/2 inch rock down to fines
• Compacts into a firm, load-bearing layer
• Best capped with a finer course for the finish

In stock now. Request a quote for 2 1/2 Inch Base Course delivery on the Big Island.