15 Questions to Ask a Roofer Before Replacing Your Flat Roof

A commercial flat roof replacement is one of the largest capital expenditures most property owners and managers will authorize in a given year. The difference between a 30-year roof and a 15-year roof often comes down to decisions made before the first crew arrives on site. Those decisions are shaped by the questions asked during the quoting process.

This post covers the 15 questions every building owner, property manager, and facility director should ask a roofing contractor before approving a flat roof replacement quote. A printable checklist version is available at the bottom of the post.

Download the checklist (PDF). 15 questions, printable, for use in your next quote meeting.

1. What percentage of your annual work is commercial and industrial flat roofing?

A contractor whose core business is residential shingles or general exteriors will approach a flat roof project differently than a firm that works exclusively on commercial and industrial buildings. The trades, equipment, manufacturer certifications, and crew skills are not the same. For a commercial flat roof, we would want to hear that at least 80 percent of the contractor’s annual revenue comes from commercial and industrial flat roofing work.

2. How many commercial flat roof replacements have you completed in the last 12 months?

Recent project volume tells you whether the crews are actively working on similar roofs today, or whether the contractor’s experience is drawn from work done five or ten years ago. For commercial and industrial flat roofs in Ontario, a healthy contractor is completing between 20 and 80 replacements per year depending on their size. Ask for a list of recent projects within the last 12 months, and be prepared to request references.

3. Are you certified by the manufacturer of the system you are quoting?

Built-up roofing, modified bitumen, EPDM, TPO, and PVC systems all carry manufacturer certifications that authorize a contractor to install the product and issue the manufacturer warranty. A contractor who is not certified by the manufacturer cannot offer the full manufacturer warranty, and their installation may not be backed in the event of a material defect claim. Ask which manufacturers the contractor is certified by, and ask to see current certification documentation.

4. What is the full scope of the quoted work, line by line?

Two quotes for the same roof can differ by tens of thousands of dollars because the scopes are not the same. A line-item scope of work should cover tear-off (partial or full), insulation type and thickness, vapour barrier, cover board, membrane system and number of plies, flashing detail, drain work, penetration work, and any structural repairs. If the quote is a single lump sum with no line items, request a detailed breakdown before comparing it to any other quote.

5. Is the scope a tear-off or a recover?

Recover (installing a new roof over the existing membrane) is faster and less expensive than a full tear-off, but it is not always the right choice. Building code limits the number of membrane layers, and recovers trap any moisture currently in the existing assembly. For a roof nearing end of life, a tear-off is usually the better long-term decision. For commercial roofing across Toronto and the surrounding GTA, the building condition and existing insulation state should drive this call, not the price gap.

6. What insulation spec are you quoting, and what is the R-value?

Ontario’s building code sets minimum R-values for commercial flat roofs, and the right specification depends on the building’s use, the existing assembly, and energy code compliance. A lower-R quote can look cheaper, but it may be non-compliant, or it may cost the building owner significantly more in HVAC operating costs over the roof’s life. Related reading: R-value for flat roofs explained.

7. Will you be reusing any existing insulation, and if so, how are you assessing its condition?

Reusing sound insulation is a legitimate cost-saving and sustainability measure when the existing insulation is dry, structurally intact, and meets current R-value requirements. It is not a shortcut that any contractor should offer blindly. Ask how the contractor will assess insulation condition (moisture meter readings, core samples, visual inspection) and how they document the findings. Learn more about insulation reuse on commercial flat roofs.

8. How will drainage be addressed on this roof?

Ponding water is one of the single largest drivers of premature flat roof failure in Ontario. A quote that does not address existing drainage issues, or does not specify tapered insulation where it is needed, is likely to underperform within the first 10 years. Ask how the contractor plans to achieve positive drainage, whether tapered insulation is included in the quote, and how existing drains will be repaired or replaced.

9. Who is doing the actual installation work?

Some roofing contractors subcontract the installation to third-party crews rather than using their own employees. This is not inherently a problem, but it can create accountability gaps on warranty issues, safety incidents, and quality control. Ask whether the crews are in-house or subcontracted, and if subcontracted, how the contractor manages quality and safety oversight on site.

10. What is your WSIB clearance status and liability insurance limit?

For commercial and industrial work, we recommend two million dollars in liability insurance as the minimum, and five million as a stronger benchmark for larger buildings and multi-property portfolios. WSIB clearance should be current and verifiable. A reputable contractor will provide a current certificate of insurance and WSIB clearance certificate on request, without delay. Videl carries $5M in liability insurance on every job.

11. What does the manufacturer warranty cover, and what does the workmanship warranty cover?

These are two separate warranties, and the difference matters. The manufacturer warranty covers material defects, typically for 15 to 25 years depending on the system. The workmanship warranty covers the contractor’s installation, typically for 2 to 10 years. Ask for both in writing, with the start date, coverage scope, and claim process clearly defined. A contractor who cannot produce both warranty documents in writing should not be on the shortlist.

12. What is your safety record on commercial and industrial projects?

Commercial and industrial roofing is a high-risk trade, and safety incidents on site can delay the project, create liability exposure for the building owner, and indicate a contractor with weak field supervision. Ask about the contractor’s recent safety record, any reportable incidents in the last three years, and how safety is managed daily on site. Further reading: Canadian roofing accidents and what they tell you about a contractor.

13. How will you minimize disruption to building operations during the project?

Most commercial buildings cannot shut down during a roof replacement. Tenants continue to work, deliveries continue to arrive, and HVAC systems need to stay running. Ask how the contractor sequences the work, how they manage noise, odour, and debris, and how they coordinate around tenant schedules. The answer will vary by project, but a contractor with commercial experience will have a clear process.

14. What is the project schedule, and what happens if weather delays the work?

A realistic commercial flat roof replacement schedule depends on roof size, complexity, and crew availability. More importantly, weather delays are normal in Ontario and need a clear plan. Ask for the target start date, estimated duration, and what happens if rain or snow interrupts mid-project. A contractor should have a protocol for securing the roof overnight and during weather events to prevent water intrusion during the work.

15. What does the ongoing maintenance plan look like after the roof is installed?

A new flat roof is the start of a 25-to-30 year asset, not the end of the project. The roofs that last the longest are the ones that receive scheduled inspections, minor repairs as issues emerge, and documented condition reports year over year. Ask whether the contractor offers a preventative roof maintenance plan, what it includes, and what it costs annually. A contractor that does not offer structured maintenance is a replacement-first business, not a lifecycle partner.

Download the checklist (PDF). 15 questions, printable, for use in your next quote meeting.

Red flags to watch for during the quoting process

A few patterns show up consistently on contractors who should not be on a shortlist. If any of the following appear, treat them as disqualifying unless the contractor can give a credible explanation.

• The quote is a single lump sum with no line-item scope of work.
• The contractor will not put the warranty terms in writing.
• References from the last 12 months are not available.
• The contractor pressures for a signature before other quotes have been reviewed.
• The quoted price is dramatically lower than other bids on the same scope.
• The contractor cannot produce a current certificate of insurance or WSIB clearance on request.
• The contractor does not want to walk the roof before quoting, or quotes from satellite imagery alone.

How we handle these questions at Videl Roofing

Every question above is one we expect to be asked on a commercial flat roof quote, and every answer we provide goes into the written proposal. Our quotes include a full line-item scope of work, the manufacturer system specification, insulation and drainage detail, warranty terms for both the manufacturer and our workmanship, the crew structure for the project, and the proposed start date. We walk every roof before quoting, and we include a 50+ point condition assessment in the process.

For property owners and managers evaluating whether a replacement is actually the right next step, our Preventative Roof Maintenance Plan often extends the life of an existing roof by 5 to 10 years. Not every roof needs to be replaced the year it is first flagged as a concern. A proper assessment comes first.

Comparing commercial flat roof companies?

Commercial flat roof replacement decisions made without proper quote scrutiny compound into premature failure, warranty disputes, and unplanned capital calls. The 15 questions in this post are the ones that surface the information needed to compare quotes honestly.

If you are evaluating a flat roof replacement, learn more about our flat roof replacement service, then call (905) 397-1198 or contact us online for a free quote.