Using Number 3 Stone Under Asphalt

Number 3 is smaller than number 2 and is sometimes used as a lower or middle base. It still should not be the only layer if the top is too open for paving. Ask the quarry for the gradation. A number in one state may not match another.

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Smaller than number 2, still a base rock

Number 3 is the smaller neighbor of number 2 in a lot of quarry talk. The pieces are still coarse compared with a dense-graded cap, and they are sometimes used as a lower course or a middle course in a driveway base. Smaller than number 2 does not mean it is sand, and it does not mean it is ready for a paver. If the top of the layer is too open, hot mix will not sit at a true thickness and the screed will chase holes. In that case number 3 should not be the only layer. Add a finer cap, or a thin choke if the section calls for one, so the paving grade is tight. The job of the coarse layer is support and bridging. The job of the top stone is a surface you can pave.

Ask for the gradation, not the digit

Do not assume a number from one state matches another. Call the quarry and ask what their number 3 is, or ask for the gradation. A quote that only says number 3 can be a different rock from the pile you saw on a job last year. If they offer a dense-graded product under a different name for the top, that may be the cap, while number 3 stays below. Write the product name on the order. For tons, measure the finished thickness of that layer, convert cubic yards as area times feet of depth divided by 27, and multiply by about 1.4 only as a planning default. The quarry ticket is the real weight. A different unit weight replaces 1.4. Do not weigh number 3 with the asphalt density of 145 pounds per cubic foot.

Middle layer means the stack still adds up

A lower course, a number 3 middle, and a fine cap are three thicknesses. Add the stone tons after you convert each one, and do not forget the cap because it looks thin. Skipping it on the order is how the paver shows up to an open grade. Compact each lift. A plate will not densify a deep loose pile of number 3 just because you make more passes. The asphalt above the finished cap is its own math, square feet times inches times 145 divided by 24,000, and the plant ticket is the real mix weight. Extra base width past the mat is extra stone area. Measure it with the number 3 if that layer is the one that sticks out. Then the tickets, not the size nickname, tell you what arrived.

A practical sequence

Treat number 3 as smaller than number 2, often a lower or middle base.
Cap it if the top is too open to pave on.
Ask the quarry for the gradation instead of trusting the number alone.
Convert each stone layer to planning tons and confirm them on the quarry ticket.

The mistake to skip

Assuming number 3 means the same rock in every state and paving on it with no cap.

Questions people ask

How is number 3 different from number 2?

Number 3 is smaller than number 2 and is sometimes used as a lower or middle base rather than the coarsest bottom rock. It can still be too open to pave on directly. Ask the local quarry for the gradation, because the number does not travel cleanly from one place to another.

Do I weigh number 3 like asphalt?

No. Stone is planned near 1.4 tons per cubic yard, and asphalt is planned near 145 pounds per cubic foot. They are different materials. The quarry ticket is the real weight of the number 3. The plant ticket is the real weight of the hot mix on top.

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