How Many Tons of Asphalt for a Carport Pad?

A one-car carport is often about 12 by 20 feet, about 4.4 tons at 3 inches. A two-car pad is often about 20 by 20 feet, about 7.3 tons at 3 inches. Set post footings before you pave. Send roof water away from the asphalt edge. These tons are a planning estimate.

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Start with a footprint, then the formula

Carport sizes vary, so measure the roof you are building. A common one-car planning footprint is about 12 by 20 feet, which is 240 square feet. A common two-car footprint is about 20 by 20 feet, which is 400 square feet. Use compacted hot mix at 145 pounds per cubic foot. Tons equal length times width times inches divided by 12, times 145, divided by 2000. For the 12 by 20 pad at 3 inches, 240 times 3 divided by 12 is 60 cubic feet. Times 145 is 8,700 pounds. Divided by 2000 is 4.35 tons, about 4.4 tons. For the 20 by 20 pad at 3 inches, 400 times 0.25 is 100 cubic feet, times 145 is 14,500 pounds, divided by 2000 is 7.25 tons, about 7.3 tons. Both are planning estimates. The plant ticket is the real weight.

Posts and the order of work

Posts need real footings, not a hole punched through the mat after it is paved. Sleeve or set the posts before you pave, and keep the asphalt from hugging a wood post in a way that traps water against it. If you pave first and auger later, you crack the new mat and leave a rough patch around every column. The footing concrete is not part of the asphalt tons. Tell the paver where the posts will be so the screed and the roller have a plan. A carport that is open on the sides still carries cars, so the thickness should match the vehicles, not only the roof. A 3-inch planning figure is a conversation for cars on a sound base. It is not a code thickness for a truck that lives under the roof.

Water off the roof

Carport roofs dump a sheet of water at the drip line. If that water lands on the asphalt edge and then runs under the mat, the edge breaks and the base softens. Extend the pavement past the drip, or carry the roof water away in a gutter so it does not discharge on the joint between asphalt and soil. Slope the pad so water leaves instead of sitting under the car. A birdbath under a roof stays wet longer because the sun does not dry it. Do not add the roof area into the asphalt tons. Add only the paved area, including any apron outside the posts that you choose to pave. Handwork around posts can make the ticket a bit higher than the flat formula. Say that when you order, and still treat 4.4 and 7.3 as planning numbers for those two example sizes.

A practical sequence

Measure the pad you will pave, using 12 by 20 or 20 by 20 only as examples.
Run length times width times inches over 12 times 145 divided by 2000.
Set or sleeve post footings before the asphalt is placed.
Carry roof water away from the asphalt edge and label tons a planning estimate.

The mistake to skip

Paving first and then cutting post holes through the new mat.

Questions people ask

Are 4.4 tons and 7.3 tons the prices?

They are planning weights, not prices. About 4.4 tons is the 12 by 20 foot example at 3 inches, and about 7.3 tons is the 20 by 20 foot example at 3 inches, both at 145 pounds per cubic foot. Your pad may be a different size or thickness. The plant ticket is the real weight. Ask the contractor for money. This math only checks tons.

Does the carport roof change the asphalt thickness?

The roof does not carry the cars. The vehicles and the base do. A car pad can be planned like a car driveway if the soil is firm. A truck that parks under the roof needs a thicker conversation. What the roof does change is water. Keep the drip line from eroding the edge. Set posts before paving so the mat is not cut up afterward.

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