Roofing bids look alike on the cover page and differ underneath. Two proposals for the same membrane system can carry different insulation thicknesses, different warranty terms, and very different assumptions about the deck under the existing roof.
The base bid is rarely the hard part. The work is in the tear-off assumptions, the deck replacement unit price, who flashes the curbs and drains, and whether the warranty the specification calls for is the one actually offered.
Typical scope items
What a complete roofing bid usually prices, and what to check in each:
| Scope item | What to check |
|---|---|
| Tear-off and disposal of the existing roof | Check the number of existing layers assumed. A bid that assumes one layer will come back with a change order if there are two. |
| Deck inspection and repair | Usually priced as a unit price per square foot of decking, sometimes with a quantity included in the base bid. Compare the included quantity as well as the rate. |
| Insulation and cover board | Confirm thickness or R-value, tapered layout and crickets, and whether a cover board is included or offered as an alternate. |
| Membrane system | Membrane type, thickness and attachment method (adhered, mechanically fastened, ballasted) should match the specification, or the bid should say it does not. |
| Flashings, curbs and penetrations | Base flashing at walls and curbs, pipe penetrations, and pitch pockets. Count what the bid says it flashes. |
| Sheet metal: coping, edge metal, gutters and downspouts | Often split between roofing and a separate sheet metal package. Make sure it is carried exactly once. |
| Manufacturer warranty | Term in years, whether it is a no-dollar-limit warranty, and any wind speed rating. Warranty differences can be worth more than the price difference. |
| Hoisting, staging and temporary protection | Crane or hoist, dumpsters, and protecting the building while the roof is open. |
Common exclusions and qualifications
Not every exclusion is a problem. Some are fair because the work belongs elsewhere. The ones below are where roofing bids most often differ, so read them against the other bidders.
| Often excluded | Why it matters |
|---|---|
| Deck replacement beyond an included quantity | Normal, but the unit price that applies after the included quantity has to be leveled too. |
| Disconnecting and resetting rooftop equipment | Usually left to the mechanical and electrical trades. Someone has to carry it. |
| Wood blocking and nailers | Sometimes roofing, sometimes carpentry. A frequent gap. |
| Roof drains, overflow drains and leaders | Plumbing typically furnishes and installs drains; roofing flashes them. Read both trades together. |
| Abatement of hazardous materials | Almost always excluded. If the existing roof may contain asbestos, plan for it separately. |
| Permits, bonds and sales tax | Compare what each bidder includes before comparing totals. |
Alternates to watch
- Tapered insulation or crickets added to the base system
- Longer warranty term or upgraded warranty type
- Thicker membrane than the base specification
- Cover board added under the membrane
- Replacing skylights, roof hatches or walkway pads
Line alternates up by the numbers on your bid form, keep add and deduct straight, and treat an unpriced alternate as a question, never as zero.
Unit prices and allowances to compare
- Deck replacement, per square foot
- Wet insulation removal and replacement, per square foot
- Wood blocking, per linear foot
- Additional layers of existing roofing removed, per square
Compare rates only where the units match, and note any quantity already included in the base bid.
Where roofing meets other trades
Gaps and double counts happen at the edges. Read these packages together:
- Sheet metal (coping, edge metal, gutters)
- Plumbing (roof drains and overflows)
- Mechanical (curbs, equipment disconnect and reset)
- Carpentry (blocking and nailers)
How Bidtab lays out roofing bids
Upload each bidder's PDF to one project for the package. Bidtab reads every bid and shows, side by side and in the order you uploaded them:
- each base bid, as stated;
- alternates aligned by number and description, with add or deduct for each bidder;
- a scope row for each item the bids address, with every bidder marked Included, Excluded, Qualified or Not stated;
- allowances and unit prices, with their units;
- each bidder's exclusions and qualifications as written;
- open questions where a bid is silent on an item other bidders addressed, where a figure isn't printed on the page it came from, or where line items don't add up to the total.
Every figure shows the page and words it came from, and the whole comparison exports to an Excel workbook. Bidtab doesn't rank bidders or price excluded scope; those calls stay with you. The sample project is a roofing package, so you can see exactly how it looks.