Procurement Guide
The hardest part of buying a commercial roof is not getting prices; it is comparing them. Three contractors can bid the same building and submit three numbers that are not measuring the same thing, because each has made different assumptions about tear-off, insulation, deck repair, and warranty. The owner who awards on price alone is usually awarding on whoever excluded the most scope. Our job on the owner side is to normalize bids so you are comparing identical work, then evaluate the terms that determine what the roof actually costs over its life. This guide walks through how to read a roof bid the way an advisor does, line by line, before any number is compared.
Start by Normalizing the Scope
Before comparing any two prices, confirm that both bids describe the same roof assembly. A reroof bid should state the system (TPO, PVC, EPDM, modified bitumen, or coating), the membrane thickness in mils, the attachment method (mechanically fastened, fully adhered, or ballasted), the insulation type and R-value, and the cover board. When one bid quotes a thinner membrane or a lower R-value, it will be cheaper for reasons that have nothing to do with the contractor being more competitive.
The single largest swing between bids is usually the treatment of the existing roof. A tear-off to deck is a different project than a recover over the existing membrane, and code limits how many roof layers a building may carry. If one contractor priced a recover and another priced a full tear-off, the numbers are not comparable, and the recover may not even be permissible. Establish the assembly first; compare price second.
Read the Exclusions Before the Inclusions
The exclusions section is where a bid tells you what it is not responsible for, and it is the most informative part of the document. Deck replacement, wet-insulation removal, and metal work are frequently excluded and then surface as change orders once the roof is open. We read every bid for the following common carve-outs:
- Deck repair or replacement, usually priced per square foot as a unit rate if priced at all.
- Wet or damaged insulation removal, often excluded entirely and billed as discovered.
- Sheet metal, coping, counterflashing, and edge metal, which can be a large omitted line.
- Overburden, mechanical units, walkway pads, and lightning protection removal and reset.
- Permits, engineering, structural upgrades, and code-triggered improvements.
A bid that excludes deck and insulation work without stating unit rates is an open-ended commitment. We require unit prices for the predictable unknowns up front, so that the inevitable change orders are priced before the contractor has leverage, not after.
Decode the Warranty Terms
Warranty length is the number owners fixate on and the one that means the least without its terms. The meaningful distinction is between a manufacturer's NDL (no-dollar-limit) system warranty and a contractor's workmanship warranty, which cover different things for different durations. A twenty-year manufacturer warranty does not cover installation defects in year two; the contractor's workmanship warranty does, and it is often only one or two years. We read warranties for:
- Whether the manufacturer warranty is NDL system or material-only, and whether labor is included.
- The contractor's separate workmanship warranty term, which covers early installation failures.
- Ponding-water and drainage exclusions that can void coverage on a flat roof.
- Maintenance and inspection conditions the owner must document to keep coverage valid.
A warranty is a contingent liability transfer, and its exclusions define how much liability actually transferred. The cleanest twenty-year warranty on the bid stack is worth more than the longest one if the longest one excludes the failure mode your building is prone to.
Test the Assumptions Behind the Number
Every bid rests on assumptions about quantities the contractor has not verified. Square footage taken from a satellite measurement, an assumed deck condition, an assumed number of drains and penetrations, and an assumed wind-uplift requirement all flow into the price. We pressure-test these by asking how the roof was measured, whether a core cut was taken to confirm the existing assembly, and what wind-uplift rating the attachment was designed to. A bid built on an unverified assembly is a bid built on a guess, and the guess becomes your change order.
We also confirm the basics of contractor qualification: that the firm is a certified applicator for the manufacturer whose warranty is being offered, since the NDL warranty is only available through certified installers. A bid offering a manufacturer system warranty from a contractor not certified for that system cannot deliver the warranty as written.
Comparing on Total Cost, Not Bid Price
Once scope is normalized, exclusions are mapped to unit rates, and warranties are read for their exclusions, the bids can finally be compared on equal terms. The right comparison is total expected cost over the hold period: bid price, plus the probable change orders the exclusions imply, weighed against the warranty coverage and expected service life each system delivers. Frequently the lowest bid carries the highest probable total cost once its exclusions are priced in, and the apparent premium on a complete bid turns out to be the honest number.
Document the comparison: the normalized scope, the exclusion-to-unit-rate mapping, the warranty terms accepted, and the rationale for the award. That record justifies the decision to ownership, protects you in any future warranty claim, and gives whoever manages the building next a clear account of what was bought and why. A roof bid read carefully is a negotiation you win before signing; read carelessly, it is a series of change orders you lose afterward.