The short answer
Whoever the contracts make responsible for protecting the glass, and whoever the evidence shows caused the damage. In practice that turns on three things: the contract language, the condition record before the final clean, and the type of scratch. This is general information; ask your counsel about your contracts.
The usual suspects
| Possible cause | What it often looks like |
|---|---|
| Other trades | Splatter, overspray or tool marks in work areas |
| Debris dragged across the glass | Scratches running in the cleaning direction |
| Scraping heat-treated glass | Fine scratches across large areas |
| Fabrication or handling | Damage present before installation, or at the edges |
These are patterns, not proof. A specialist assessment and the condition record carry more weight.
The evidence that matters
- Contract clauses on glass protection and damage responsibility
- Photos and a written condition record before the final clean
- The cleaning methods agreed in advance, and whether they followed NGA guidance
- Glass quality standards for the product, such as ASTM C1036 for flat glass and ASTM C1048 for heat-treated glass, which set how glass is inspected for blemishes
Fix it before turnover
Arguments about who pays can run for months. Glass restoration can often remove surface scratches faster than replacement glass can be ordered, so the building opens on time while responsibility is sorted out.
- Get a restoration assessment with a test area
- Compare the restoration scope with replacement lead time and cost
- Document before and after for the record
Prevent it on the next project
- Glass protection written into the general contractor's scope
- A condition walk with photos before the final clean
- Cleaning methods agreed in advance
- The window cleaner involved early
S&K's post-construction cleanup handles final-phase glass and site cleaning. See post-construction final clean: scope, sequencing and handoff.
Not sure what you are looking at? Use the glass and metal damage triage guide, read the full Facade, Glass, and Metal Restoration guide, or have our team assess the surface and recommend the right approach, in writing.
