First question: replacement or recover?
The model International Building Code (Section 1512 in the 2024 IBC, 1511 in 2021) defines roof replacement as removing all existing layers down to the deck. A recover, installing new roofing over the existing covering, is allowed in listed cases, but not where:
- the existing roof is water-soaked or deteriorated so it is not an adequate base,
- the existing covering is slate, clay, cement or asbestos-cement tile, or
- the existing roof already has two or more applications of any roof covering.
Core samples or a moisture survey (infrared, nuclear or capacitance) tell you which applies. Local amendments change details, so check the adopted code.
Energy code: the insulation upgrade nobody priced
Under the 2021 IECC (C503.2.1), a roof replacement where the existing roof has insulation entirely above the deck must meet current insulation requirements (Table C402.1.3 R-values or C402.1.4 U-factors), and insulation cannot be reduced. Recovers and repairs are generally exempt if energy use does not increase. Related provisions in the same edition:
- Continuous insulation in at least two layers with staggered joints.
- At least 1 in. of above-deck insulation at the lowest point (drain, scupper or gutter edge).
- Tapered insulation R-value calculated from average thickness.
- Cool roof requirements in climate zones 0 to 3 over cooled spaces.
Thicker insulation raises the roof surface, which can push curbs, wall flashings, edge metal, door thresholds and scuppers out of compliance. That is the hidden scope: curb extensions, taller edge metal and wood blocking, and mechanical disconnect and reset.
Scope sections
| Section | What to state |
|---|---|
| Preparation | Protection, access, hoisting, permits, fall protection, interior protection |
| Tear-off | Existing layers by type and number, insulation, disposal; asbestos survey results |
| Deck | Inspection and replacement at a unit price per sq ft or per sheet |
| New system | Manufacturer system, insulation R-value and layers, tapered design, cover board, membrane, attachment, wind uplift rating |
| Flashing | Walls, curbs, penetrations, edges, counterflashing |
| Accessories | Drains, scuppers, vents, edge metal, gutters, walkway pads |
| Closeout | Cleanup, manufacturer inspection, warranty type and term |
Flashing heights and rooftop equipment
NRCA guidance calls for base flashings at least 8 in. above the finished roof surface. After an insulation upgrade, many existing curbs and wall flashings fall short. Count every curb and record its height on the site walk; decide who disconnects, raises and resets units (usually the mechanical contractor), and say so.
Quantities
| Item | Unit | Notes |
|---|---|---|
| Roof area | SF or squares (100 SF) | True area for sloped roofs |
| Tear-off | SF by layer | Layers from cores |
| Insulation | SF by thickness; tapered by layout | Tapered layouts are often supplied by the manufacturer |
| Edge metal and coping | LF by profile | Include wood blocking raise |
| Wall flashing | LF by height | Parapets measured separately |
| Curbs and penetrations | EA by size and type | Pipes, vents, supports, conduit |
| Drains and scuppers | EA | Replace, retain or add inserts |
| Deck replacement | Unit price per SF or sheet | Quantity unknown until tear-off |
An 18,000 sq ft low-slope roof on metal deck. The bid carries 500 sq ft of deck replacement at a unit price, and the unit price applies to quantities above or below.
Without the unit price, every sheet of deck found at tear-off becomes a negotiation.
What changes the price
- Roof height, access, crane or hoist needs and material staging.
- Occupied building: noise, odor (kettles, adhesives), hours and interior protection.
- Weather and temporary waterproofing: only open as much roof as can be made watertight the same day.
- Asbestos: EPA's asbestos NESHAP requires a thorough inspection before renovation of regulated facilities; older built-up roofs, mastics and flashing cements may contain asbestos, which requires licensed abatement where present.
- Fall protection: OSHA 1926.501(b)(10) covers work on low-slope roofs; warning lines, guardrails, safety monitors and personal fall arrest each have cost.
- Wind uplift: specs may require an FM Global approval rating or ASCE 7 design pressures, which drive fastener density at corners and perimeters.
Sample scope language
"Remove existing roofing down to the structural deck, including two layers of built-up roofing and insulation, approximately 18,000 sq ft. Inspect deck and replace deteriorated metal deck at the unit price below; 500 sq ft included. Install two layers of polyisocyanurate insulation with staggered joints to the R-value required by the adopted energy code, with tapered insulation to existing drains, cover board, and fully adhered single-ply membrane. Replace edge metal and counterflashings; raise wood blocking as required. Raise curbs at RTU-1 through RTU-6 to maintain 8 in. minimum flashing height; disconnect and reset of units by others. Provide manufacturer's 20-year NDL warranty as specified."
Each phrase answers a question that otherwise becomes a dispute: how deep the tear-off goes, how deck repairs are priced, which insulation and how drainage works, what happens at edges and curbs, who moves equipment, and which warranty is included.
Common exclusions
- Structural repairs beyond the deck unit price.
- Mechanical and electrical disconnect and reconnect of rooftop equipment.
- Hazardous material abatement.
- Interior protection beyond stated measures.
- Permits, if obtained by the owner.
Where an item is likely but its quantity unknown, a unit price is more useful to both parties than an exclusion.
Where RenderDraw fits
RenderDraw's AI takeoff proposes roof areas, edges and penetrations from drawings with sources, for estimator review before pricing. Try a free sample takeoff.
