Window installation failures — water infiltration at improperly flashed frames, air leakage from inadequate sealing, fogged glass units that fail prematurely — are among the most common home improvement complaints in many regions. Here’s what to do when you discover the work wasn’t done correctly.

“Document the problem before you call anyone. A photo of water staining on the interior trim after a rain event, combined with a photo of the missing or improperly applied flashing on the exterior, tells the whole story. Without that documentation, you’re in a he-said-she-said situation. With it, you have evidence.”

— Marcus Webb, building science consultant and ENERGY STAR program participant with 12 years of experience advising homeowners on window and insulation upgrades in the local area

Step 1: Document the Problem Thoroughly

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Before contacting the contractor, before filing any complaint, before any repair is done:

  • Photograph the interior symptoms — water staining on trim or drywall, condensation patterns, visible gaps at the frame, failed caulking
  • Photograph the exterior — improperly applied or missing flashing tape, gaps in caulking, windows that appear unlevel or poorly fitted
  • Note when you discovered the problem and what conditions preceded it (a rain event, cold weather, etc.)
  • Record the history — when the windows were installed, who installed them, what was promised, what was paid
  • Preserve all documents — the original quote, the contract, any warranty documentation

Step 2: Understand Your Consumer Protection Rights

Window purchases made following a door-to-door sale or other direct sales approach in many regions are subject to the applicable consumer-protection law, which provides:

  • A 10-day cooling-off period — if you’re within this period and haven’t had the work done yet, you can cancel without penalty
  • The right to cancel within one year if the required contract disclosures weren’t made
  • Remedies if the company engaged in unfair practices

Contact your local consumer protection office (1-800-889-9768 or ontario.Ca/consumerprotection) to understand your specific rights.

Step 3: Contact the Contractor in Writing

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Notify the contractor in writing — by email — describing the problem clearly:

  • What the specific issue is (water infiltration at window X, fogged glass at window Y, etc.)
  • When you discovered it
  • What damage has resulted
  • Your expectation that it’s covered under the workmanship warranty

Give the contractor a reasonable time to respond — 5–10 business days. Keep records of all responses.

Step 4: Get an Independent Assessment

If the problem is significant or the contractor disputes responsibility, hire an independent building inspector or building envelope consultant to assess the installation. Their written report objectively identifies what went wrong — missing flashing, improper air sealing, failed glass seal — and distinguishes between an installation failure, a product defect, and a manufacturer warranty claim.

This report is the foundation of any warranty claim, complaint, or legal action.

Step 5: File Complaints with Relevant Authorities

Your local consumer protection office: File a complaint for unfair business practices, misleading sales representations, or failure to honor warranty obligations.

Better Business Bureau: Creates a public record of the complaint.

If the company belongs to a professional association (WDMA, CWDMA, local home builders’ association): File a complaint through the association.

Step 6: Manufacturer Warranty Claim

If the issue is a product defect — a glass seal failure, a hardware failure within the warranty period — contact the manufacturer directly with your purchase documentation and evidence of the defect. Ask whether the manufacturer warranty covers the repair.

Note: If the installer wasn’t certified by the manufacturer, the enhanced warranty may not apply. This is why manufacturer certification matters at the hiring stage.

Step 7: Small Claims Court

For unresolved financial disputes within the regional limit (up to $35,000 in many regions), small claims court is an option. You’ll need the original contract, the independent assessment report, evidence of the damage, and records of all communications.

Prevention: The Questions That Would Have Helped

Most window installation failures are traceable to one of three things at the hiring stage: an unverified installer without manufacturer certification, an installation approach that skipped proper flashing, or a warranty that was less comprehensive than represented. Asking the right questions before hiring remains the most effective protection.

See: Questions to Ask a Window and Door Contractor Before You Hire One

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