Planning Guide

How to prepare openings and site conditions for commercial glazing

Most commercial glass problems are not glass problems. They are opening problems: a slab that runs out of level through a door swing, a header that deflects, a ceiling that was not final when the partition was measured, a freight elevator that the panel does not fit in. This guide is for owners, tenants, general contractors and property managers who want the glazing package on a storefront, entrance, interior front or guard to go in once, on the agreed date, without a second fabrication order.

Why readiness matters more than the glass

Tempered and laminated glass leave the fabricator at final size. A storefront lite that is half an inch too tall because the sill was raised after the measure cannot be trimmed; it is remade. An aluminum frame fabricated to a square opening will not sit in one that is racked, and the gap shows up as a sealant joint that is too wide on one side and non-existent on the other. Every one of those outcomes costs more time than the readiness check that would have prevented it, and it is why a glazing contractor working on a planned basis will move a measure rather than measure an unfinished opening.

What “ready” means for each opening type

The questions change with the opening. A storefront in new construction is mostly about the structure and the weather line; an interior front is about finishes; a guard is about substrate and the project's loading determination. The table sets out the readiness questions and the holds we see most often.

The rough opening: size, square, plumb and level

A rough opening has a nominal size on the drawing and an actual size on site, and the glazing is made to the second. The verification records daylight width and height at several points, the diagonal difference that reveals racking, plumb of each jamb, and the level of the sill or floor across the full width. In door openings the floor is checked across the whole swing, because a leaf that clears the threshold at the hinge and drags at the latch is a floor problem no hardware adjustment fixes.

In existing buildings — converted warehouses, Old Town masonry, older strip retail — the opening is rarely square and the drawing is rarely right. That is not a defect to be argued about; it is the reason the fabrication measure exists. Our storefront measurement and estimate checklist lists what a proper storefront survey records.

Substrate and anchorage

Every frame and every guard anchors to something, and the anchorage is designed for that something. Storefront framing wants a head that will not deflect onto it under load, jambs that can take fasteners, and a sill on a level, sound base. Interior fronts need a ceiling or soffit that can carry a head channel and floors that can take a sill channel without finding a post-tension tendon or an in-floor service. Guards are the most demanding: a base shoe needs a slab edge or steel with enough depth and strength for the shoe's loads, and a timber deck usually needs blocking added before anything is fixed. The substrate and attachment readiness guide goes through the guard case in detail.

Flashing, waterproofing and the sill

Exterior glazing sits on the building's weather line, and the weather line is not the glazier's scope. Before a storefront is measured, the weather barrier should be terminated to the opening, the sill flashing installed and the sill itself level and sound. Where a guard base shoe penetrates a deck or roof membrane, the detail around the penetration needs an owner — the waterproofing or roofing contractor, or the general contractor — assigned before installation, so the fixing and the membrane repair are designed together. Water damage found below an old storefront sill during verification is a scope change; it is far cheaper to price while the frontage is still in service than after the old frame is out.

Finishes that must be final before the measure

Interior glass is measured to finished surfaces. The floor must be levelled and its final finish either installed or its exact thickness known; the ceiling grid, soffit or drywall the head channel fixes to must be in place; adjacent walls must be plumb, finished and painted where the glass or frame will meet them. A partition measured to a bare slab and an open ceiling is a guess, and glass fabricated to a guess is the most common reason an interior glazing package is installed twice. Our office glass partition planning guide covers layout and door decisions that should be settled before this point.

Power, access control and hardware coordination

Door hardware is where glazing meets the electrical and security trades. Electrified strikes, magnetic locks, card readers, request-to-exit devices and automatic operators all need power and conduit in specific places, and several of them change the frame preparation. Decide the hardware set before the frame or leaf is fabricated, confirm where power is roughed in, and name the trade that terminates each device. Our guide to commercial glass door types and hardware explains the options; the coordination point here is simply that they are decided early.

Access, lifting and staging

Panel size is limited by what can be fabricated, transported, carried through the building and lifted safely into the opening — and on most urban sites the third and fourth limits bite first. Walk the route: alley or loading dock, door widths, freight elevator interior dimensions and weight limit, corridor turns, stair landings, and the space in front of the opening to stage glass and set up lifting equipment. Where a sidewalk or traffic lane is needed for a lift, confirm who arranges it and when. A lite that cannot reach its opening is discovered on installation day if nobody walked the route — and in a converted downtown building it is a common discovery.

Sequencing with other trades

Glazing is late-sequence work with long-lead fabrication behind it, which makes it easy to squeeze from both ends. The sequence that works has three hold points agreed with the general contractor: a pre-measure walk early enough to flag structural or access problems while they are cheap to fix; a fabrication measure after the opening and its finishes are final; and an installation window that follows fabrication and precedes the trades that need the glass in — millwork, flooring transitions, final paint at the frame. Move any of those and the others move with them. What does not work is a fabrication measure taken early to protect the installation date; it protects the date at the cost of the fit.

A readiness checklist to send with your enquiry

Sending these with a request for pricing lets a glazing contractor quote the opening that exists and flag the holds before they cost anything.

• Drawings or a sketch of each opening with nominal sizes, plus photographs from both sides.
• The structure the frame or guard anchors to: concrete, steel, CMU, timber, blocked stud wall.
• Which openings are exterior and how the weather barrier, flashing and sill are being handled — and by whom.
• Floor and ceiling status: levelled, finished, or still to come, and the date each will be final.
• Door hardware intent: closers, locks, panic hardware, access control, automatic operators, and where power is roughed in.
• The route from the truck to each opening: alley, loading dock, freight elevator dimensions, sidewalk or lane use.
• Trading or occupancy constraints and any after-hours rules from building management.
• Hold points already agreed with the general contractor: pre-measure walk, fabrication measure, installation window.

Questions we are asked about readiness

When should the glazier measure a commercial opening?

After everything the glass depends on is final: framing, floors, ceilings, adjacent finishes and, for exterior openings, the sill and flashing. Glass cannot be trimmed on site once it is fabricated, so measuring before those items are complete trades a short schedule gain for a real risk of misfit. A pre-measure walk earlier in the job is useful for planning; the fabrication measure waits.

Who is responsible for the rough opening being square and to size?

The trade that builds it — framer, mason or concrete contractor — under the general contractor. The glazing contractor verifies the opening and reports what is there; it does not correct the structure. Agreeing the acceptable tolerances in writing before framing starts avoids the argument about whose problem an out-of-square opening is.

What happens if the opening is not ready on the measure date?

The honest answer is that the measure moves. Measuring an unfinished opening and fabricating to assumptions is how glass arrives that does not fit. The better outcome is a short delay to the measure and a fabrication order based on the opening that exists.

Does the glazier handle waterproofing around a storefront sill or a guard base shoe?

Usually not. The membrane, flashing and the repair of any penetration through them belong to the waterproofing, roofing or general contractor scope. The glazing contractor needs to know who owns that detail before installation so that the fixing method and the membrane detail are designed together rather than discovered in conflict.

Where to go next

• Storefront glass and aluminum entrances — what a storefront system is made of and how field verification runs.
• Commercial glass systems — choosing between storefront, curtain wall, partitions and entrances.
• Local commercial planning: storefront glass in Denver, commercial storefront glass in Fort Collins and commercial glass in Colorado Springs.
• For architects, contractors and property managers — scope boundaries and what to send for pricing.
• How to prepare for a glass site measure — the residential and small-project version of this checklist.