Exterior Glass: Keep It From Becoming a Last-Minute Change Order

Where exterior glass gets lost

Glazing subs usually clean their own labels and sealant off the glass, not the construction dust and overspray that build up afterward. Many cleaning bids say "windows" without saying which side. By the time anyone notices, the lift is gone and the landscaping is in.

Decide who owns it

• Put exterior glass in exactly one subcontract, the cleaning sub or the glazing sub, and say so in writing.
• Say whether "windows" means interior, exterior or both. Also say whether frames, sills, mullions and tracks are included.
• Name canopy glass, skylights, storefront transoms and interior glass partitions separately. These are the items most often missed.

Count it the right way

Glass should be priced by openings or panes counted from the elevation drawings, not by the building's gross square footage. A bid priced only by building area is a guess. Ask which elevation sheets the bidder used.

Plan the access

• Ground-level storefront: ladders and poles.
• Two to four stories with clear ground access: water-fed poles are often enough.
• Higher glass, glass over landscaping or canopies, or soft ground: a boom lift, and someone has to carry it.

If a lift is already on site for high dusting or another trade, keeping it a day or two longer costs much less than mobilizing a second one. Coordinate that before it goes off rent.

Time it after the dirty work

• Clean exterior glass after exterior sealant, masonry cleaning, painting and most site work.
• Do it before final landscaping and mulch if a lift has to drive near the building.
• Expect a light second pass if the glass sits through more site work after cleaning.

Protect the glass

Construction debris, paint and stucco on glass are often removed with a blade. Tempered and coated glass can scratch, so the cleaner should test in an inconspicuous spot and follow the glass manufacturer's cleaning guidance. Get any existing damage documented before cleaning starts.

Spec language you can use: "Cleaning subcontractor shall clean all interior and exterior glass, frames, sills and mullions, including storefront, canopy and transom glass, after completion of exterior sealant and site work. Subcontractor shall furnish all access equipment required."