What This Article Covers
Sidelight frames are fixed-glazed frame sections installed beside an active door opening to add light, visibility, or architectural presence. This guide explains how sidelight frames are constructed, what options and limitations apply in commercial hollow metal and specialty applications, and what questions to answer before you place an order. It is written for contractors, facility managers, and architects who need to specify or procure the right frame assembly the first time.
What Is a Sidelight Frame?
A sidelight frame (also called a borrowed light frame when used without a door nearby) is a frame profile designed to hold fixed glazing adjacent to a door opening. Unlike a door frame, a sidelight frame has no hinge or strike prep and does not swing. It is part of the total elevation assembly -- the combined width of the active door opening plus the sidelight panel or panels.
In commercial construction you will find sidelight frames at school main entries, healthcare reception corridors, retail storefronts, and industrial security checkpoints where natural light or sightlines are required alongside a controlled door.
KD vs. Welded Sidelight Frames
Most commercial hollow metal sidelight frames are available in two construction methods:
- Knock-down (KD): Shipped flat and assembled on the job site with common hand tools. No welding or special prep required. This is the most common choice for drywall steel-stud construction and fast-track projects. KD sidelight frames in the C-series (drywall) profile can be set in a matter of minutes.
- Welded: Factory-assembled as a rigid unit. Required for masonry applications needing maximum rigidity, or when the frame gauge or configuration falls outside KD limits.
Key Construction Variables to Specify
Profile Type
Sidelight frames share profile families with standard door frames. The C-series drywall profile is the most common for interior and commercial steel-stud applications. Profile face widths typically range from 1-1/2 in. through 2 in. for standard applications, with sill face options extending to 6 in. where a sill condition requires it. The profile you choose must match the wall thickness and the door frame profile it meets.
Steel Gauge
Sidelight frames are available in 16-gauge cold rolled and A60 galvanized steel for most standard applications. Where the elevation is exposed to moisture -- such as vestibule entries at schools or healthcare drop-off zones -- galvanized or galvannealed options reduce long-term corrosion risk significantly.
Overall Elevation Limits
Sidelight frame assemblies have maximum overall elevation dimensions that govern ordering. For standard KD drywall sidelight frames, check the manufacturer's published limits for overall width and height before specifying. As a practical reference, a common maximum active door opening in a sidelight assembly is 4080 (4 ft. 0 in. wide by 8 ft. 0 in. tall), with the sidelight area making up the remaining overall width. Confirm the exact limits for your chosen product line at order entry.
Mullion Orientation
Standard sidelight frames use vertical mullions only. Horizontal mullions divide the sidelight area into stacked lights and are not available on all KD sidelight frame configurations. If your design requires horizontal divisions, confirm availability before specifying -- this is a common coordination miss that delays fabrication.
Fire Rating
Many KD sidelight frame products are non-rated. If the opening requires a fire label, the entire assembly -- door, sidelight panel, glazing, and frame -- must be coordinated as a listed assembly. The fire rating of the sidelight panel governs the glass selection; not all vision glass is appropriate for rated sidelights. When in doubt, require the frame manufacturer's fire listing documentation before finalizing the spec.
Hurricane and High-Wind Zones
In HVHZ regions (such as Broward and Miami-Dade counties in Florida) and other design-pressure environments, sidelight frame assemblies must carry the appropriate windstorm label. This affects anchor type, frame gauge, glazing specification, and the total allowable elevation width. Assemblies tested to ASTM E330, E1886, and E1996 standards are available, but the sidelight area dimensions are tightly constrained -- typically a maximum sidelight area width of 12 in. for tested assemblies at high design pressures. Do not assume a standard frame ships with hurricane compliance; verify the label at order entry.
Glazing and Glass Stop Details
Sidelight frames are typically factory-prepped for a specific glass thickness. The glass stop -- the trim that holds the glass in the frame -- is usually a channel section applied on both sides of the glazing in the field. Aluminum sidelight frames used with FRP (fiberglass-reinforced plastic) door systems may use an 11/16-in. high by 1/2-in. wide channel glass stop, field applied. Verify the glass stop profile matches the glazing thickness specified and confirm whether glazing is factory or field installed for your frame type.
Anchor and Wall Coordination
Sidelight frames must be anchored to the surrounding wall structure the same way door frames are -- plumb, level, and square. For steel-stud walls, the jamb studs must be continuous from floor to ceiling runner alongside the sidelight frame. Common anchor options include masonry T-anchors, wire anchors for new masonry construction, and steel-stud snap-in anchors for drywall applications. Store frames off the ground on wood runners, protect from moisture, and set a wood spreader at the head and base to maintain opening width during installation.
Hardware Considerations at the Sidelight
Because sidelight frames hold fixed glass rather than an active door, standard door hardware does not apply directly to the sidelight section. However, the adjacent active door frame must still be fully coordinated:
- Hinge location and backset on the active frame must be confirmed before the sidelight mullion position is set.
- If the active opening uses an exit device, confirm the device does not project into or conflict with the sidelight mullion when the door swings open.
- Thresholds and weatherstripping at the sill must be continuous across the sidelight base if the assembly is at an exterior location.
- For electrified hardware at the adjacent active door, verify that power transfer routing does not conflict with the sidelight frame anchor locations.
Common Ordering Mistakes to Avoid
- Specifying a KD sidelight frame without confirming the maximum overall elevation width for that product line.
- Requesting horizontal mullions on a frame line that only supports vertical mullions in KD construction.
- Assuming a non-rated KD sidelight frame can be used in a fire-rated corridor assembly without a listed configuration.
- Omitting the sill face dimension -- sill faces from 1-1/2 in. through 6 in. may be available, but the default is not always what the field condition requires.
- Mismatching the sidelight frame profile to the active door frame profile, creating a visible joint mismatch at the mullion.
Getting the Spec Right the First Time
Sidelight frame orders that arrive incomplete or miscoordinated cause delays that ripple through the door and hardware schedule. Before you submit an order or RFI, have answers to these questions: overall elevation width and height, active door opening size, wall type and stud gauge, fire rating requirement (yes or no), design pressure requirement (if applicable), glass thickness and glazing method, and whether horizontal mullions are required.
The team at DoorwaysPlus works with contractors and specifiers on sidelight frame assemblies across commercial, school, healthcare, and industrial projects. If you have an elevation drawing or a schedule question, reach out at DoorwaysPlus.com for product guidance and pricing.