Post-Construction Scratched-Glass Liability Checklist

Why this matters

Post-construction window cleaning is one of the most profitable service lines in a window-cleaning business and one of the most dangerous from a liability standpoint. The crew arrives, the glass has paint flecks and stucco splatter on every pane, and aggressive cleaning with razor blades and scrapers produces what looks like scratched glass on hundreds of pieces in a finished commercial building. The general contractor's punch-list inspector then claims the cleaner caused the scratches and demands the cleaner pay for the glass replacement. The defense is not "we did not scratch the glass." The defense is a documented inspection-and-acknowledgment procedure executed before the cleaner ever touches the glass. This SOP is the procedure that protects the business.

The science of fabricating debris

The scratches that show up after post-construction window cleaning are almost always not caused by the razor blade. They are caused by fabricating debris already embedded in or fused to the glass surface from the manufacturing process. When a razor blade is dragged across glass with fabricating debris on the surface, the debris is dragged along with the blade, ploughing a track across the glass that looks like a fresh scratch. The blade did not cause the scratch; the blade revealed the scratch path that the debris always could have made if anything dragged across the glass with enough pressure.

The Glass Association of North America (GANA, now part of the National Glass Association) published the GANA Glass Informational Bulletin GANA 01-0116 (Heat-Treated Glass Surfaces Are Particularly Susceptible to Scratching) and the related guidance that fabricating debris fused to heat-treated glass surfaces is a manufacturing condition, not a cleaning-induced defect.

This is the technical foundation of the cleaner's defense. The defense only works if the cleaner can document the pre-cleaning condition.

The pre-cleaning walkthrough

Before any tool touches any glass, the lead technician walks the building with the general contractor or the GC's representative and documents:

1. The condition of every visible pane: clean of construction debris (rare), light splatter (common), heavy splatter requiring scraping (also common).
2. Any glass that shows visible defects: bubbles, inclusions, surface haze, distortion, edge chips. These are pre-existing defects of the glass itself.
3. Any glass that shows fabricating debris: small embedded particles visible when the glass is viewed at a low angle in good light. Mark these panes with painter's tape and photograph.
4. Any glass that has heat-treatment markings (tempered "T" marks, laminated edge marks). Heat-treated glass is the most susceptible to fabricating-debris scratching.

The walkthrough produces:

• A photo set of every elevation at low and direct angle.
• A spreadsheet or checklist of any specifically-marked panes with pre-existing defects.
• A signed acknowledgment from the GC's representative that the walkthrough was conducted and the pre-existing conditions were observed.

The walkthrough takes 1 to 4 hours depending on building size. The time is paid for in the bid, not absorbed.

The acknowledgment language

The acknowledgment is the document the cleaner produces months later when the punch-list dispute arises. Sample language:

The undersigned representatives of [General Contractor] and [Window Cleaning Company] have jointly conducted a pre-cleaning visual inspection of the glass on the project at [address] on [date]. The glass surfaces are observed to have construction debris (paint, stucco, mortar, sealant, mineral deposits) requiring scraper and chemical cleaning. The parties acknowledge that aggressive cleaning of construction debris from glass may reveal pre-existing surface defects including fabricating debris fused to the glass surface, and that such defects are conditions of the glass manufacture and installation, not conditions caused by post-construction cleaning. The parties further acknowledge that the cleaning will be performed in accordance with the International Window Cleaning Association (IWCA) best practices for post-construction cleaning, including the use of new razor blades on each pane, glass-rated lubricant during scraping, and immediate cessation of scraping on any pane that shows scratching with the first pass.

Both representatives sign and date. Each party keeps an original.

If the GC will not sign the acknowledgment, the cleaner has two choices: decline the work, or accept the work with the documented understanding that the acknowledgment was offered and refused (which is itself documentation, but weaker than a signed acknowledgment).

The first-pass test

Even after a signed acknowledgment, the IWCA-recommended cleaning practice protects against unnecessary damage. On any post-construction project, the cleaner runs a first-pass test:

1. Select one or two test panes that are representative of the building's glass.
2. Apply abundant glass-rated lubricant (water with a drop of detergent is the minimum; a commercial scraper lubricant is better).
3. Make a single, deliberate scraper pass with a fresh razor blade in a single direction (never back and forth) at a low angle (approximately 30 degrees).
4. Inspect the pane immediately at low angle in direct light.
5. If scratches are visible, stop. Do not continue with the scraper on this glass.
6. If no scratches are visible, continue with the same technique on additional panes, with regular re-inspection.

The first-pass test catches problem glass before the crew has scratched the entire building. If the test glass scratches, the cleaning approach changes: chemical-only cleaning, gentle abrasive pad cleaning, or referral back to the GC for an alternative approach (sometimes the glazier is brought back to re-polish or replace problem panes).

On-tool technique

Even healthy glass is damaged by sloppy technique. Standard practice:

References

• IWCA International Window Cleaning Association best practices for post-construction window cleaning.
• GANA Glass Informational Bulletin GANA 01-0116 (Heat-Treated Glass Surfaces Are Particularly Susceptible to Scratching), National Glass Association.
• ASTM C1036 Standard Specification for Flat Glass, governing glass-surface quality classifications.
• ASTM C1048 Standard Specification for Heat-Strengthened and Fully Tempered Flat Glass, governing heat-treated glass standards.
• National Glass Association Fabricating Glass Manual, technical guidance on glass surface conditions and fabricating debris.
• OSHA 29 CFR 1926 Subpart M, Fall Protection, applicable to post-construction work above 6 feet.