What This Article Covers and Who It Helps
Transom frames appear on opening schedules for schools, hospitals, office buildings, and industrial facilities whenever glazed panels, borrowed lights, or fixed sidelights sit above a door opening. Getting the transom frame construction right before the order ships saves field headaches, prevents code conflicts on fire-rated assemblies, and keeps the door schedule on track. This guide is written for commercial subcontractors, facility project managers, and architects coordinating hollow metal frame submittals.
What Is a Transom Frame?
A transom frame is a hollow metal frame profile that encloses a fixed panel -- glass, louver, or solid infill -- positioned above the door opening. The horizontal member separating the door opening from the transom panel is called the transom bar (sometimes called a transom crossbar or transom rail). The transom bar carries load from the panel above, transfers it to the jambs, and typically provides the frame stop against which the panel is set. The full assembly -- door frame plus transom bar plus transom frame -- is ordered and fabricated as one coordinated unit.
The Three Core Construction Decisions
1. Integral vs. Slip-On Transom Bar
On a welded frame, the transom bar is factory-welded to the jambs, forming a rigid, one-piece assembly. This is the preferred approach for masonry construction and fire-rated openings because dimensional control is locked in at the shop. On knocked-down (KD) frames, the transom bar may be a field-assembled slip-on component -- faster to ship and carry on site, but it requires careful field alignment to maintain the door opening height and panel opening height within tolerance.
- Welded transom frames: tight dimensional control, required for many fire-rated assemblies, heavier to handle on site.
- KD transom frames: field-assembled, easier to stage in occupied buildings, must be checked for squareness before grouting or drywall closure.
2. Rabbet Configuration and Panel Thickness
The transom frame profile must match the panel it receives. Equal-rabbet profiles center a panel of uniform thickness. Unequal-rabbet profiles accommodate glazing stops where the panel is set from one side -- common when glazing must be replaceable from the corridor side only, as in healthcare and school corridor applications. Confirm panel thickness (including any glazing tape or setting blocks) before specifying the frame stop dimension. A mismatch forces field modifications that can void a fire label.
3. Fire Rating Coordination
When the door opening is fire-rated, the transom assembly above it must carry a compatible fire rating. A rated transom frame must be ordered as a labeled assembly -- the frame label covers the full opening including the transom section. The glazing in the transom panel must itself be rated for the appropriate fire period (20-minute, 45-minute, 60-minute, 90-minute) and listed for that use. Fire-rated glazing is not interchangeable with standard glass, and the frame label does not cover an unlisted panel. Coordinate with the door and frame supplier early -- adding a transom label after the fact is not a field fix.
Dimension Coordination: Where Orders Go Wrong
The most common submittal error on transom frames is a mismatch between the door opening height, the overall rough opening height, and the transom panel height. These three dimensions must account for:
- Door slab height (typically 7'0" or 8'0")
- Transom bar height (the bar itself takes up vertical space -- confirm the manufacturer's standard bar height, which varies by profile series)
- Transom panel height (the clear daylight opening of the panel above the bar)
- Frame depth (must match wall thickness including finish material)
- Head clearance at the rough opening (standard frame tolerance is nominal width plus or minus 1/8" on each side; apply the same discipline vertically)
Architects and hardware coordinators should dimension the transom panel height explicitly on the door schedule rather than leaving it as a remainder calculation. Framers ordering from a schedule that shows only total rough opening height and door height have made the transom panel height error more than once on the same job.
Wall Type and Anchor Selection
Transom frames must be anchored to the structure above the panel opening, not just at the jambs. In masonry construction, the head of the transom frame is grouted and anchored to the masonry. In drywall (steel stud) construction, the frame head relies on the stud framing above -- if the stud layout does not provide a solid anchor point at the frame head, the transom section will rack under load. Confirm anchor locations with the framing sub before the frame is set, and confirm that slip-on KD transom components are torqued and locked before the wall is closed.
Before grouting masonry frames -- including transom frames -- coat the interior of the frame with bituminous water-resistant paint. Moisture migrating from grout into bare metal causes rust from the inside out, damage that is invisible until the frame is severely compromised.
Hardware Implications at the Transom Bar
The transom bar is occasionally used as a mounting surface for overhead concealed closers or for header-mounted magnetic holders on hold-open assemblies. If a concealed closer body is to be housed in the frame head above the door, confirm that the frame head profile has sufficient depth for the closer body and that the supplier has been given the closer model before fabrication. This is a coordination point between Section 087100 hardware and Section 081113 hollow metal -- it cannot be resolved after the frame ships.
Key Questions to Answer Before You Order
- Is the overall opening fire-rated? If so, is the transom panel glazing rated for the required fire period?
- Welded or KD construction -- which does the wall type and project schedule favor?
- What is the panel material and thickness, including glazing tape and stops?
- What is the explicit transom panel height (not a remainder calculation)?
- Are overhead closer or holder preps required in the transom bar or frame head?
- What anchor conditions exist at the frame head in the rough opening?
Get the Frame Right the First Time
Transom frame construction touches door scheduling, fire-rating compliance, glazing selection, and hardware coordination all at once. DoorwaysPlus.com carries hollow metal frames and can connect you with the technical support to review your opening schedule before the submittal goes out. Getting the dimensions and rating requirements confirmed early costs nothing. Sending a wrong frame back to the shop costs time, money, and schedule.
Browse hollow metal frames and coordinating door hardware at DoorwaysPlus.com or contact our team for project-specific guidance.