How to bid glazing work as a subcontractor

What you are actually bidding

The glazing package is a bundle of separate specification sections, and the money leaks at the seams between them. On a typical commercial job the sections in play are:

• 08 43 00 Storefronts and 08 44 00 Curtain Wall and Glazed Assemblies. Aluminum framed storefront at grade, curtain wall above.
• 08 50 00 Windows. Punched aluminum or fiberglass windows set into a masonry or stud backup wall. Different install, different perimeter condition, different crew than storefront.
• 08 80 00 Glazing. Glass make-up, interior glass, mirrors. Read glazing if the division numbering is new to you.
• 08 90 00 Louvers and Vents. Specified in Division 08, performance rated by the mechanical engineer, drawn on the architectural elevations.
• 08 71 00 Door Hardware and the entrance sections, plus 07 92 00 Joint Sealants and whichever section carries the air and water barrier.

Six boundaries decide whether the job makes money:

1. Perimeter seal and the barrier tie-in. Your frame has to marry the wall's air and water barrier. The details show a transition membrane lapped onto the frame flange and almost never say whose hand installs it. Decide, then write it down.
2. Backing and sub-framing at openings. Head, jamb and sill sub-framing in metal stud walls, steel tube behind tall mullions, and steel angle or a lintel over openings can sit with you, the framer, the mason or the steel sub. It is never obvious from the elevation.
3. Interior glass and mirrors. Usually in your spec section, installed months later, after the drywall finish. That is a second mobilization, not a rounding error.
4. Glass doors and their hardware. All glass entrances, patch fittings, floor closers, panic devices and closers. See door hardware sets and confirm whether your hardware is in your number or in the door package.
5. Louvers. Frame and blade are yours. Blank off panels, ductwork behind and the free area certification are usually mechanical.
6. Delegated design. Structural calculations, anchor design and a stamped submittal for the curtain wall are engineering cost, not overhead.

Read the drawings for your sheets

• A-series elevations tell you where the systems are, not how big they are. They are drawn to read as a facade, often with one bay dimensioned and the rest noted similar.
• The window and storefront schedules govern. Sizes, types, glass make-up, finish and performance come from the schedule, not from scaling. Scaled elevations produce wrong lite sizes and a wrong count, because the schedule is where the odd units and the mirrored bays are listed.
• Wall sections plus the head, jamb and sill details carry the real scope: receptors, sill pans, flashing, the window sill condition, backer rod and joint width, and the slip joint at the head for live load deflection.
• Structural sheets give you slab edge conditions, embeds, cast in anchor plates and the deflection criteria you have to design to.
• Mechanical sheets tell you which openings are louvers and what free area they need.
• The specification carries what the geometry cannot: air and water infiltration limits, U factor and solar heat gain coefficient, deflection limits for members supporting glass, delegated design responsibility, mockup requirements and field testing frequency.

Getting the quantities right

Glazing is bid in square feet of glass by make-up and linear feet of frame by system type, with each (ea) for doors, louvers and mirrors. Take the frame off by system, get the lf per member type from the schedule and the details, and take the glass off lite by lite.

What the obvious square foot takeoff misses:

• Fabricators bill by lite, not by area. Most price lists round each lite up and apply a minimum billing size, so a wall of small vision lites bills as if the lites were larger than they are, and panes above the jumbo threshold carry an oversize surcharge. Get the current minimum billing size and oversize breaks from your fabricator and price your takeoff the way they will invoice it.
• Glass make-up is set by code and by exposure, not by preference. Safety glazing locations drive tempering: glass in a door, glass within a short arc of a door edge, large panes with a low bottom edge next to a walking surface, glass near wet areas and at stairs. Sloped and overhead glazing generally requires laminated glass. Thickness comes from the wind load, not the drawing.
• Spandrel is not vision glass. Heat strengthened or tempered spandrel, opacifier or shadow box, and an insulated back pan behind it. The back pan is sheet metal work that is often shown on no sheet at all and lands on you.
• Perimeter sealant volume follows the real joint, not the drawn one. A quarter inch joint on a detail becomes a much wider joint against a real slab edge or masonry tolerance. Wider joints mean more sealant, larger backer rod, and sometimes a deeper receptor to cover the gap.
• Mullion count comes from the schedule and the details. Expansion mullions at stack joints, corner mullions and reinforced jambs at wide bays are extra material the elevation does not show.

Delegated design, mockups and field testing

If the drawings delegate curtain wall design, you are buying a licensed engineer's time for calculations, anchor design and thermal movement, plus a review cycle before fabrication starts. Price it as a line item and say you priced it.

Then read the testing paragraphs. Visual mockups, lab performance mockups and field testing to the standards named in the spec, commonly water penetration and air leakage tests such as ASTM E1105, ASTM E783 and AAMA 501.2, are priced per test at a frequency the spec sets. If the spec says one test per a given area of wall and you carried one test, you gave the difference away. Say how many tests you included and what a retest costs.

What the GC checks when leveling glazing bids

Bid leveling is the GC normalizing every glazing proposal to one scope. Expect them to check:

• System types and glass make-up, against the schedule and the spec, line by line.
• Who seals the perimeter and who ties into the air and water barrier, including the transition membrane and the interior air seal.
• Sub-framing, backing and anchors. In or out, and who supplies cast in plates.
• Interior glass, mirrors and glass doors, and whether hardware is included.
• Louvers, and where the blank off panels sit.
• Delegated design, mockups and field test counts.
• Approved shop drawings duration and lead time on glass and finish, because your enclosure date drives their schedule.
• Allowances carried, and for what.
• Hoisting, protection and final glass cleaning, which are commonly excluded and rarely stated.

Anything left silent gets filled in with an assumption that does not favour you.

Structure the proposal

Put the number first, with the system types and spec sections it covers. Then inclusions as items, not a paragraph. Then exclusions, which is the most valuable section in the document. Then clarifications and assumptions: shop drawing review duration, delegated design, glass make-up carried, test counts, slab edge tolerance assumed, hoisting and access, sequence and the interior glass mobilization. Finish with unit prices per square foot of each glass type, per linear foot of each frame type and per door, so a change is a lookup rather than an argument.

Where this fits

Glazing bids get challenged on quantity and on boundary, usually in the same phone call. If you are running the takeoff, Ruh reads the drawing set, measures the openings, and prices the measured quantities against your own price book, with every line traceable back to the sheet it came from, which is what you need when a GC asks where your glass area came from.