If you manage a commercial property in the Greater Toronto Area, your roof isn’t just overhead coverage, it’s a critical asset protecting inventory, equipment, tenants, and your bottom line. And if you’ve invested in installing a new flat roof or major restoration, chances are you’re counting on that manufacturer or contractor warranty to protect you if something goes wrong.
But here’s the hard truth: over 60% of commercial roof warranty claims are denied, not because the roof failed unfairly, but because the warranty was unknowingly voided by preventable mistakes.
The good news? Most of these pitfalls are completely avoidable – if you know what to watch for.
In this guide, we’ll walk you through the top mistakes that void commercial roof warranties in Ontario, explain why they matter, and, most importantly, show you exactly how to avoid them. Whether you’re overseeing a warehouse in Mississauga, a retail plaza in Brampton, or an industrial facility in Concord, this is the only resource you’ll need to safeguard your roofing investment.
Types Of Commercial Roofing Warranties:
Commercial roofing warranties typically come in two forms:
- Manufacturer warranties (covering materials like TPO, EPDM, or modified bitumen membranes)
- Workmanship warranties (covering the contractor’s installation quality)
Both can be invalidated – even if your roof was “brand new” just a few years ago.
Mistakes That Will Void Your Roofing Warranty Coverage
1. Hiring a Non-Certified or Non-OIRCA Contractor
Most major manufacturers (like GAF, Firestone, or Siplast) require that their roofing systems be installed only by factory-certified contractors. If your installer isn’t certified, your manufacturer’s warranty is void from day one – even if the materials are perfect.
In Ontario, there’s another layer: if your contractor is a member of the Ontario Industrial Roofing Contractors’ Association (OIRCA), they’re bound by strict standards. OIRCA members must provide a standard 2-year workmanship warranty for roofing and 1-year for sheet metal, and they can’t offer longer terms. But here’s the catch: using a non-OIRCA contractor doesn’t automatically give you better coverage, it just means their warranty terms aren’t standardized, which can lead to loopholes or unenforceable promises.
How to avoid it:
- Always verify that your contractor is certified by the manufacturer of the roofing system you’re installing.
- Ask if they’re an OIRCA member – this signals adherence to provincial industry standards.
- Request proof of certification and check it directly with the manufacturer if needed.
2. Skipping Required Inspections or Failing to Register the Warranty
Extended commercial warranties – especially No Dollar Limit (NDL) or pro-rated system warranties – often require mandatory inspections at key stages: during installation, after completion, and sometimes annually. Miss one, and the warranty may be void.
Similarly, many manufacturers require online or paper registration within 30–90 days of installation. If this step isn’t completed (and it’s often the contractor’s responsibility), your warranty doesn’t exist, even if you paid for it.
How to avoid it:
- Get a written schedule of all required inspections and registration deadlines.
- Confirm with your contractor that registration has been submitted – and keep a copy of the warranty certificate.
- Set calendar reminders for annual inspections if your warranty requires them.
3. Allowing Unauthorized Roof Modifications
Need to add HVAC units, solar panels, satellite dishes, or new roof hatches? These are common on commercial buildings – but if they’re installed by anyone other than your original roofing contractor (or without manufacturer approval), you’ve just voided coverage in that area – and possibly the entire roof.
Why? Because membrane roofs are sealed systems. Drilling, cutting, or flashing a penetration incorrectly compromises the integrity of the entire assembly. Manufacturers won’t cover leaks around an unauthorized rooftop unit – even if the rest of the roof is fine.
How to avoid it:
- Never allow third-party vendors (HVAC techs, solar installers, etc.) to cut into your roof without prior coordination with your roofing contractor.
- Request that your roofer install all flashing and penetrations as part of the original job, or return to handle modifications under warranty.
- If modifications are needed later, contact your original contractor first and get written confirmation that the work won’t void coverage.
4. Neglecting Routine Maintenance
Commercial warranties almost always include a “duty to maintain” clause. This means you’re responsible for keeping drains clear, removing debris, inspecting for ponding water, and addressing minor issues before they escalate.
For example, if leaves clog your roof drains for months, leading to standing water that exceeds 48 hours (a common threshold in membrane warranties), the resulting membrane failure won’t be covered – even if the material itself is defect-free.
How to avoid it:
- Implement a biannual roof maintenance plan (spring and fall), plus post-storm checks.
- Keep detailed logs of all inspections, cleanings, and minor repairs – these records are crucial if you file a claim.
- Consider hiring your original contractor for maintenance – they understand your system and can spot warranty-threatening issues early.
5. Using the Wrong Repair Methods or Materials
A small leak doesn’t mean you should grab the nearest patch kit or call a handyman. DIY repairs or using non-approved materials (like generic sealants or mismatched membrane patches) are considered “unauthorized alterations” and instantly void coverage.
Even worse: some temporary fixes trap moisture beneath the membrane, accelerating decay and making the original problem far worse.
How to avoid it:
- Never attempt DIY repairs on a commercial flat roof.
- Only allow factory-trained technicians to perform repairs using manufacturer-approved materials from the same system.
- If you have an emergency leak in your flat roof, call a qualified commercial roofer, don’t “band-aid” it and hope for the best.
6. Installing Over an Existing Roof Without Approval
While “re-covering” (installing a new membrane over an old one) can save money upfront, most manufacturers void warranties if this is done without engineering approval – especially if the existing roof is wet, damaged, or lacks proper slope.
Ontario building codes also restrict re-covering in many cases. If your roof deck isn’t inspected and prepared correctly, the new system can fail prematurely, and your warranty won’t cover it.
How to avoid it:
- Always opt for a full tear-off and inspection unless a structural engineer and manufacturer both approve a re-cover.
- Ensure your contractor provides documentation that the substrate meets warranty requirements.
7. Ignoring Ventilation and Drainage Requirement
Flat roofs rely on proper slope and drainage to shed water. If your roof has ponding water for more than 48 hours after rainfall, many warranties consider this a maintenance failure.
Similarly, poor ventilation in roof assemblies (especially on buildings with occupied attic spaces or mechanical rooms) can lead to condensation, insulation saturation, and membrane delamination, none of which are covered if deemed preventable.
How to avoid it:
- Ensure your roof was designed with adequate slope (minimum ¼” per foot) and functional drains/scuppers.
- Inspect for standing water after every rain event.
- Address low spots with tapered insulation or slope correction. Please don’t ignore them.
Maintain Your Roofing Warranty With IRSL
A commercial roof warranty isn’t a “set it and forget it” safety net. It’s a contract with responsibilities on both sides. By avoiding these common mistakes, you keep your coverage intact and your property protected.
And remember: the best warranty in the world won’t help if your contractor cuts corners or vanishes after the job is done. Choose a reputable, certified, and locally experienced roofing partner who understands Ontario’s climate, codes, and commercial roofing standards.
Need a Warranty-Safe Roofing Partner in the GTA?
At Industrial Roofing Services Limited, we’re a Concord-based commercial roofing contractor serving Toronto, the GTA, and Southern Ontario with certified installations, OIRCA-aligned workmanship warranties, and proactive maintenance plans designed to keep your roof – and your warranty – in full force.
If you’re planning a repair, replacement, or emergency leak fix, contact us today for a FREE flat roof inspection. We’ll make sure your roof meets every manufacturer’s requirement, so your warranty stays valid for years to come.