Extruded Asphalt Curb Versus Header Curb

Extruded asphalt curb is a raised edge paved on the surface, often over tack, and it can crack loose if it is stuck only to sealer or a dirty mat. A header is a formed edge, sometimes concrete or timber, that the asphalt paves against. Extruded curb is not a structural wall.

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A raised bead paved on the mat

Extruded asphalt curb is formed by a machine that lays a raised asphalt edge, often on a surface that has been tacked so the bead can bond. It steers water and marks the edge of a lot or a drive. It is asphalt, so it can crack, and it can peel off if it is stuck only to sealer or to a dirty, dusty mat. Ask the quote whether the curb is extruded asphalt, and ask what the surface under it will be. Tack on that line is the crew's bond coat. It explains the bid. It is not a weekend plan to spray tack and run a curb machine. Look at a nearby extruded curb that has been through a winter. The ones that failed usually let go at the bottom, in a sheet.

A header is the edge you pave against

A header is a formed edge. It might be concrete, a timber, or another solid form. The asphalt is paved against it and compacted to full thickness at that face. The header stays, and the mat ends cleanly. That is a different object from a bead of asphalt stuck on top. Ask which one the quote includes, because the words curb and header get swapped. A timber header rots if it stays wet, and a concrete header is its own pour. Neither one is created by the paver as it passes. If you need the asphalt tons, measure to the header and use about 145 pounds per cubic foot. A 10 by 40 foot panel at 2 inches is 400 times 2 divided by 12, times 145, divided by 2,000, about 4.8 tons as a planning estimate. The plant ticket is the real weight.

Neither curb holds a steep fill by itself

Extruded curb is not a structural wall. It will not hold a driveway that is trying to slide down a steep fill. If the edge is a drop-off, you need a designed retaining edge, a wider base, or both, and you should ask someone who designs that condition. A header can give the mat a clean stop and still not be a retaining wall unless it was built as one. Keep water from sitting behind the curb. A bead that dams the only outlet creates ice and a soft base. When the curb cracks loose, do not glue it down with driveway sealer. Replace the bond on a clean mat, or switch to a header if the bead keeps failing. Say plainly on the quote which edge you are buying before the machine shows up.

A practical sequence

Ask whether the edge is extruded asphalt curb or a formed header.
Put extruded curb on clean asphalt with the crew's tack, not on sealer or dust.
Pave full thickness against a header, and keep header material out of the asphalt tons.
Do not expect either edge to retain a steep fill unless it was designed to.

The mistake to skip

Extruding curb onto sealer or a dirty mat and watching the bead peel off in sheets.

Questions people ask

Why does extruded asphalt curb come loose?

It is a raised bead bonded to the surface. Sealer, dust, or a weak tack line lets it crack free at the bottom. Tack on a quote is the crew's bond coat on clean asphalt, not a do it yourself spray. A header curb is different: a form you pave against. Extruded curb is not a wall that holds a steep fill.

Is the curb included in the asphalt tons?

Ask. An extruded curb uses some mix, and the quote should say how it is measured. A concrete or timber header is not hot mix. The mat paved up to a header plans near 145 pounds per cubic foot. A 10 by 40 foot panel at 2 inches is about 4.8 tons as a planning estimate. The plant ticket is the real weight.

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