Glazing Installation: Shop Drawings, Setting Glass & Water Management

Welcome

Hello, and welcome. This is Super Structures General Contractors — a national general contractor headquartered in Powhatan, Virginia — here to help you and your clients build something that lasts. We're glad you're with us, and we look forward to connecting with you.

Here's one that matters more than its name lets on — Glazing Installation: Shop Drawings, Setting Glass & Water Management. If you remember one thing, make it this: Glazing is installed from the shop drawings, anchored for movement, set plumb, level, and square on proper blocking, and built so water that gets in can get out — leaks are almost always a detail that got skipped. Do this right and the field water test is a formality.

Shop drawings and field measuring

The glazing contractor's shop drawings translate the architect's elevations and details into the system: elevations with every frame tagged, horizontal and vertical sections, anchor details, glass schedules, sealant joint locations, and interface details with the roof, wall, and slab. The architect reviews them, and the field builds from them, not from the architectural set. Before fabrication, the crew field measures: opening width at top, middle, and bottom; height at both jambs; diagonals for square; plumb of the jambs; and the sill's level and elevation against the control line. Openings must leave room for the frame plus the perimeter sealant joint and shims, and must land within the system's tolerance — or the fix happens now, not when the frames arrive.

Anchors and embeds

Frames carry two loads: dead load (the weight of glass and metal) and wind load (pushing in and pulling out). Storefront anchors to the slab and the head through the frame members or clips; curtain wall hangs from embeds cast in the slab edge or post-installed anchors, with dead-load anchors at one point and wind-load anchors elsewhere that are slotted so the frame can move as the building deflects and the aluminum expands. Anchor type, spacing, and embedment come from the shop drawings and the engineer, not from whatever is in the truck.

Setting the frame

Set the sill first on shims to a laser line, dead level; set the jambs plumb in both directions; check the head; check diagonals for square; and fasten through shims so the frame isn't bowed. Keep sightlines consistent across the elevation — the eye catches a horizontal that is a quarter inch off. Install the sill flashing or sill pan with end dams and a back dam before the sill member goes down, and lap it correctly with the wall's water-resistive barrier so water drains out, never in.

Setting the glass

Clean the glazing pocket, confirm the glass is the right lite with the right coating orientation and label, place the setting blocks at the quarter points, set the glass with cups or a lifter, center it with edge blocks, and install the glazing — gaskets rolled in for dry glazing, tape with a cap bead, or a wet silicone seal — per the system. On captured curtain wall the pressure plate is torqued to the manufacturer's value and the snap cover goes on last; on structural silicone glazing the sealant is applied in a controlled sequence with cure time before the temporary clips come off.

Sealant joints and water management

The perimeter joint between frame and wall is sized for movement, gets a backer rod, and is tooled to a concave profile after the surfaces are cleaned and primed if required. Inside the system, water is managed on the assumption that some gets past the exterior seal: storefront sills are zone-dammed at each vertical with sealant so water in one bay cannot run to the next, and weep holes let it out; curtain wall is a pressure-equalized rain screen where the gasket line sheds most water and the internal gutter and weeps drain the rest. Blocked weeps, missing end dams, and unsealed horizontal-to-vertical joints are the three most common leak sources, and all three are invisible once the covers are on.

Going Deeper (Intermediate)

The architect may require field water testing: the AAMA 501.2 hose test sprays fixed joints with a calibrated nozzle to find leaks in the installed system, while ASTM E1105 uses a spray rack and a pressure chamber to test an area under a specified pressure difference. A mock-up or the first bay installed is often tested before the crew runs the rest of the elevation, so a detail problem is fixed once instead of eighty times. Laboratory ratings for air infiltration (ASTM E283), water penetration (ASTM E331), and structural performance (ASTM E330) are what the system was tested to; the field test checks that the installation lives up to them.

Advanced / Pro-Level

Pros understand movement: aluminum expands and contracts noticeably across a hot-cold cycle, slabs deflect under live load, and tall buildings drift in wind, so stack joints in curtain wall, slotted anchors, and properly sized sealant joints are what keep glass from cracking and seals from tearing. They coordinate the air barrier and water-resistive barrier transition at every opening with the waterproofer so the glazing's drainage plane continues into the wall's, and they insist on a pre-installation meeting with the GC, the waterproofer, and the sealant manufacturer's representative. They also know the design pressure on the drawings comes from ASCE 7 wind calculations, with higher pressures at corners and parapets, and they confirm the system, glass, and anchors are rated for the worst zone, not the average.

Practice Challenge

After a storm, a tenant reports water on the sill of one storefront bay while the bays on either side are dry. The frames were installed last year. Where would an experienced glazier look first? (Answer: inside that bay's sill — a missing or failed zone dam or end dam at the vertical, blocked or missing weep holes, or an unsealed horizontal-to-vertical joint; because the adjacent bays are dry, the problem is almost certainly internal to that bay's sill drainage, not the wall flashing.)

In Practice

A crew that sets the sill pan with end dams, zone-dams every bay, and passes a hose test on the first bay never gets the leak call. A crew that caulks the outside beautifully and skips the inside gets the call every time it rains.

Common Mistakes to Avoid

• Fabricating from the architectural drawings instead of field-measured shop drawings
• Omitting end dams, zone dams, or weeps because they are hidden anyway
• Setting frames out of plumb and "fixing" it by forcing the glass
• Fastening slotted wind-load anchors tight so the frame cannot move

Takeaway: Glazing is installed from the shop drawings, anchored for movement, set plumb, level, and square on proper blocking, and built so water that gets in can get out — leaks are almost always a detail that got skipped.

Educational overview only — not hands-on glazing instruction, a safety program, or a substitute for training under a qualified glazier. Follow OSHA 29 CFR 1926, the manufacturer's installation instructions, the NGA Glazing Manual, your employer's procedures, the project documents, and the building code, energy code, and contractor licensing requirements that apply where you work.