Two jobs that look the same on the proposal
Both end with a fresh black lot. Both get priced by the square foot, and both put the same paver and rollers on site. But a mill and fill and an overlay are different jobs with different costs, and a contractor who prices them off the same unit prices will win the wrong ones.
The short version: an overlay adds a lift on top of what's there. A mill and fill takes off a set depth of the old surface first, transports it off site and paves back in its place. Everything in the estimate follows from that one difference.
When each one is the right call
An overlay makes sense when the pavement underneath is structurally sound, the lot drains, and there's room to come up. Adding an inch and a half or two inches raises the grade at curbs, doors, drain structures and anywhere the lot meets concrete. If a 2-inch overlay puts the surface above the gutter lip, water goes the wrong way and you own the problem.
Mill and fill is the answer when the grade can't move, when the surface is too far gone for a new lift to bond to, or when the customer wants the trip hazards and birdbaths gone instead of buried. Milling also leaves a rough, clean surface for the new lift to grab.
Plenty of lots end up somewhere in between: the edges milled along the curb and at transitions so the overlay ties in flush, with a full lift everywhere else. Price that as what it is, with the milled footage broken out.
Neither one fixes failed base. Alligator cracking over soft base comes back through a new lift either way, so dig out and patch those areas first and price them as their own line.
The overlay estimate
An overlay is close to a straight paving estimate. Measure the net area, pick the lift thickness, figure tons and price them.
A 2-inch overlay on 30,000 square feet at 145 pounds per cubic foot is 362.5 tons (30,000 × 2 ÷ 12 × 145 ÷ 2,000). Add a waste allowance, usually more on an overlay than on a milled surface, because the old surface is never as flat as the drawing. Ruts and low spots take extra mix, and the screed doesn't know where your estimate stopped.
Then the lines you can't skip:
- Surface prep: sweeping, cleaning, and crack sealing if the spec calls for it
- Tack, so the new lift bonds to the old surface
- A leveling course if the ruts are bad: a separate thin lift before the main one
- Transitions: butt joints at the edges, milled or feathered, and adjustments at structures
- Striping and traffic control
Tack is cheap and easy to forget. It's the difference between an overlay that stays down and one that slips and peels within a few seasons. Put it on the proposal and on the foreman's work order so it doesn't get skipped when the distributor truck is late.
The mill-and-fill estimate
Everything above still applies. Now add the milling and everything milling causes.
The milling. Priced by the square yard or square foot at a set depth, with your own machine or a milling sub. Depth matters. Milling 2 inches usually isn't twice the cost of milling 1, but it does make twice the material to transport. Confirm the depth and put it on the proposal. "Mill and pave" with no depth is an argument waiting to happen.
Material transport. The millings have to go somewhere. Figure their weight from area × depth × unit weight, the same as the mix. Then remember that broken-up millings take more room in a truck than they did in the lot, so count loads by volume as well as by weight. If your plant takes RAP and credits you for it, subtract that. If you're paying to dump it, add that. Either way, it's a line.
Sweeping. The milled surface has to be clean before tack goes down. That's a sweeper and an operator for a set number of hours.
Heavier tack. A milled surface is rougher and takes more tack than a smooth one. FHWA's guidance puts milled surfaces at the top of the range, so bump your rate.
Tighter tonnage. This is the part people get wrong in the good direction. On an overlay you're paving over an uneven surface and eating the difference. The mill leaves a consistent depth, so the tons are more predictable. You still carry an allowance, just a smaller one.
Base surprises. Milling shows you what's underneath. If the base is soft, you find out when the machine drops through it, and now you have an undercut and a change order. Put a unit price for base repair on the proposal, per square foot or per ton of stone, so the conversation with the customer is "here's the quantity" instead of "here's a new number."
Same lot, two prices
Take a 30,000 square foot lot. That's 3,333 square yards if your milling sub prices by the yard.
Overlay, 2 inches: 362.5 tons plus a waste allowance, tack, sweeping, striping, and transitions at three doors and a drain structure. The risks are the grade at the curb and extra mix in the ruts.
Mill 2 inches, pave 2 inches: the same 362.5 tons with a smaller allowance, plus milling on 3,333 square yards, around 360 tons of millings to transport, sweeping, heavier tack, and a base repair unit price on the sheet. The risk is what's under the surface.
The mill and fill will come in higher, and it should. It's more work and a better result. The mistake is pricing it as "overlay plus a little for milling" and finding out on the transport line that the little was a lot.
What goes on the proposal
For either job, name the lift thickness, the mix, the tack and the striping. For a mill and fill, add the milling depth, what happens to the millings, and the base repair unit price. Those aren't details for the crew. They're what the customer signed for, and they're what settles the change order when the base gives out.
Where Pavr fits
Pavr is job management software for paving, sealcoating, striping and concrete contractors. Its built-in services include mill and overlay at depths from 1 to 3 inches, a straight overlay, a leveling course, and milling on its own or at the transitions, so the milling depth is on the estimate from the first draft, priced off your plant price and crew rates. Add a service of your own for anything the lot needs that isn't on that list. The milling depth on the proposal is the milling depth on the foreman's work order.
When the mill finds soft base, send a change order from the job. The customer signs it on their phone, the paving part of the job waits until they do, and once it's signed it's on the invoice. See how estimating works.
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