If you're a general contractor managing a paving project, milling is likely a subcontracted scope. Understanding what to specify, how to coordinate, and what to expect helps you manage the milling subcontractor effectively and avoid problems that affect your project schedule.
This guide covers the practical aspects of working with a milling subcontractor from the GC's perspective.
What to Include in Your Milling Specification
A clear milling specification includes: limits of work (plan showing exactly what areas to mill), milling depth (uniform or variable), surface texture requirements, disposal/recycling requirements for millings, and any special requirements around structures.
Specify whether depth is measured from the existing surface (uniform removal) or to a target elevation (grade correction). This distinction determines whether the milling contractor needs grade control references or can simply set a consistent depth.
Include requirements for transitions — how the milled edge meets unmilled pavement. A vertical edge (butt joint) is standard for areas that will be overlaid to the same limits. A tapered edge is needed where overlay limits differ from milling limits.
Coordination with Paving
Milling and paving must be coordinated closely. The milled surface should receive overlay within 24–48 hours for best results. Extended exposure degrades the surface quality and can allow water infiltration.
Communicate your paving schedule to the milling sub so they can plan production accordingly. If you're paving Monday, milling should happen Thursday or Friday of the previous week — not two weeks before.
Tack coat responsibility should be clearly assigned. Some milling contractors apply tack as part of their scope. Others leave it to the paving contractor. Clarify this in the subcontract to avoid gaps or double-application.
Production Planning
Milling production rates vary by depth, material hardness, and site constraints. For planning purposes, a typical commercial milling operation produces 3,000–8,000 square yards per day at 2-inch depth. Your milling sub should provide a production estimate specific to your project.
Haul truck logistics often determine production rate. If trucks can't cycle fast enough, the milling machine sits idle waiting for empty trucks. Ensure your milling sub has adequate haul capacity for the project distance to the recycling facility.
Night work reduces production rates by approximately 20–30% due to reduced visibility and additional safety requirements. Factor this into your schedule if the project requires off-peak milling.
Quality Expectations
Acceptable milling quality includes: consistent depth within tolerance (typically +/- 1/4 inch for standard work, +/- 1/8 inch for precision), uniform surface texture without gouges or ridges, clean transitions at edges and around structures, and a swept surface free of loose material.
Verify depth at regular intervals during production — not just at the end. If depth is off, it's much easier to correct during production than after the area is complete. Spot-check with a ruler or depth gauge.
Document any areas where milling depth varies from specification. This information is needed for overlay quantity calculations and may affect your paving subcontractor's material order.
Frequently Asked Questions
How do I verify milling depth?
Measure from the top of the milled surface to the top of an unmilled reference (curb, adjacent pavement, or a marked reference point). Take measurements at regular intervals — every 50 feet along the centerline and at random locations across the width.
Who is responsible for utility damage during milling?
Typically the party who failed to locate or protect the utility. If utilities were properly marked and the milling contractor hit them anyway, it's the milling contractor's responsibility. If utilities weren't marked, responsibility falls on whoever was supposed to arrange locates.
Can I use the millings on my project?
Possibly. Millings can be used as temporary surface material or base material in non-critical applications. However, using millings as structural base under new pavement requires engineering approval — RAP has different properties than virgin aggregate.
Need a milling subcontractor?
We work with general contractors across Central Florida. Discuss your project requirements and get a detailed milling proposal.