The short answer
Glass industry guidance says architectural glass must be protected through every stage of construction, and that the general contractor, the window cleaner and all trades need to communicate. It does not decide who pays for damage. Your contracts do, and documentation decides whether anyone can prove it. This is general information, not legal advice.
Who wrote the guidance
- The Glass Association of North America (GANA), whose technical work is now published by the National Glass Association (NGA)
- The International Window Cleaning Association (IWCA), which issued a joint bulletin with GANA on construction-site protection
What it says about construction sites
- Glass must be protected during all stages of construction from cement, paint, varnish, adhesives and other job-site materials.
- Conditions such as paint overspray, mortar or concrete splash, smeared sealants and sealer runoff from masonry may require more aggressive cleaning.
- Protection depends on open communication and cooperation among the general contractor, the window cleaner and every trade.
What it says about cleaning
- Identify the glass type and any exposed coatings before cleaning.
- Test-clean a small area of each glass type, then examine it for damage before proceeding.
- Most architectural glass is heat-treated, and its surfaces need greater care: scraping can drag microscopic surface particles across the glass and scratch it.
- Scrapers, abrasives and harsh chemicals are not recommended for any glass product, because they can cause irreparable damage.
What this means for liability
When scratches show up at the post-construction clean, the question is when they happened and who caused them: a trade, the debris left on the glass, or the cleaning. Contracts allocate the cost. Photos and a written condition record taken before the clean are what make the answer provable.
See scratched glass on a new build: who pays? and how to document existing facade damage.
Protect the glass, then protect the record
- Write glass protection into the general contractor's scope
- Bring the window cleaner in before the final clean, not after the damage
- Walk and photograph the glass before the final clean
- Agree on cleaning methods for construction residue in advance
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.
