Glass Transoms: How to Share Light Between Rooms Without Losing Privacy
Too Long; Didn't Read
- Interior transoms are glass panels installed above doors or between rooms to share natural light without opening the wall.
- Standard height: 10-16 inches above the door frame, filling the gap between the door header and the ceiling.
- Cost: $300-$800 per transom installed, depending on glass type and frame treatment.
- Privacy options: Frosted, reeded, or textured glass lets light through while blocking sightlines.
- No structural modification needed in most cases — the space above an interior door is non-load-bearing header area.
Answer First: An interior glass transom costs $300-$800 installed, takes 2-4 hours to cut in above an existing door, and requires no structural modification in most homes. The glass panel fills the dead space between the door header and the ceiling, sharing natural light between a windowed room and an interior space without removing any wall.
What Is a Transom?
Transom — a horizontal window or glass panel installed above a door or along the top of a wall. The term comes from the transom bar, the structural crosspiece that separates the door opening from the window above it.
In older Toronto homes — Annex Victorians, Cabbagetown rowhouses, Rosedale manors — transoms were standard. Every interior door had a glass panel above it. The reason was practical: before electric lighting, transoms channeled daylight from rooms with windows into interior hallways and closets.
Modern homes dropped them. Dropped ceilings, pot lights, and open-concept layouts replaced the need. But in 2026, transoms are coming back — not for necessity but for design. They add architectural detail, vertical proportion, and that elusive natural light that no LED can replicate.
Where Transoms Work Best
Interior Hallways
The classic application. A hallway that connects windowed rooms on either side is naturally dark. Transoms above each doorway pull light from the bedrooms and living spaces into the hall without compromising privacy (especially with frosted or reeded glass).
In Toronto's narrow Victorian rowhouses, where hallways run the full depth of the house with only a front and rear window, transoms above interior doors can eliminate the need for hallway lighting during daytime hours.
Home Offices
A room with no exterior window (common in Toronto condo dens and basement offices) benefits from a transom that borrows light from an adjacent room. Combined with frosted glass or privacy film, you get daylight without visual distraction.
Bathrooms
Transoms above bathroom doors let light enter from the hallway without a line of sight into the room. The transom position (7+ feet above the floor) is well above eye level, and frosted or textured glass adds an extra privacy layer.
Room Dividers
In open-concept renovations where a partial wall is added (for a bedroom or nursery), a transom above the partition maintains the feeling of openness and keeps the divided space bright.
Glass Options for Interior Transoms
| Glass Type | Light Transmission | Privacy | Sound Reduction | Cost |
|---|---|---|---|---|
| Clear | 90% | None | Low (STC 26-28) | Baseline |
| Frosted (acid etch) | 80% | Full obscurity | Low (STC 26-28) | +15-20% |
| Reeded | 75-80% | High — distorts shapes | Low-medium (STC 28-30) | +20-30% |
| Laminated clear | 88% | None | High (STC 34-38) | +40-50% |
| Laminated frosted | 75% | Full obscurity | High (STC 34-38) | +50-60% |
| Textured (rain, pinhead) | 70-80% | Medium-high | Low (STC 26-28) | +15-25% |
STC (Sound Transmission Class) — a rating of how much sound a material blocks. Standard drywall is STC 33-35. A clear single-pane transom at STC 26 lets more sound through than the surrounding wall. If sound privacy matters, laminated glass is the answer.
Sizing and Proportions
Standard Proportions
Most interior doors are 6'8" (80") tall. Standard ceiling height in Toronto homes is 8' (96") or 9' (108"). That leaves 16-28 inches between the door header and the ceiling — the transom zone.
Design rule: The transom should be proportional to the door below it. A 10-16" tall transom above a standard door looks balanced. Going taller than 18" starts to look like a window rather than a transom.
Width
The transom should match the door width exactly. Standard interior doors are 30" or 32" wide. The transom glass sits in the same rough opening, framed to the same width. For double doors (French doors), the transom spans the full double-width opening — 60-64".
For High Ceilings
In homes with 9-10' ceilings (common in Toronto Victorian-era homes and new custom builds), the transom space is generous. Options:
- Single tall transom — one glass panel filling the full gap
- Divided light transom — the panel is divided by muntins into two or three sections, adding a traditional grid pattern
- Transom + header trim — a smaller glass panel with decorative trim above it, maintaining proportion
Installation Process
Step 1: Assess the Wall
We check what's above the door frame. In most homes, the space above an interior door is non-structural — it's just drywall and possibly a single header board. No load-bearing elements pass through this zone.
Exception: If the wall is load-bearing and the existing header is undersized, we may need to install a wider header before cutting the transom opening. This is uncommon for interior doors but worth checking.
Step 2: Cut and Frame
- Mark the transom dimensions on the wall above the door.
- Cut the drywall on both sides.
- Frame the opening with 2×4 lumber (or match the existing wall framing).
- Install a sill piece that sits flush with the top of the door frame.
Step 3: Install Glass
The glass panel is set into a frame that matches the door trim — same profile, same paint color, same material. We use:
- Wood stops for traditional homes (painted or stained to match)
- Aluminum channel for modern/minimal looks
- Crittall-style steel frames for industrial/loft aesthetics
The glass is bedded in glazing tape or silicone, secured with stops, and sealed.
Step 4: Trim and Finish
The transom gets matching trim on both sides of the wall. We paint or stain to match the existing door casing. When done well, it looks like the transom was always there — not a renovation add-on.
Total time: 2-4 hours per transom for a straightforward installation. Larger or more complex installations (curved headers, unusual ceiling conditions) may take longer.
Cost Breakdown
| Component | Cost Range |
|---|---|
| Glass panel (clear, standard size) | $40-$80 |
| Glass panel (frosted or reeded) | $60-$120 |
| Framing and trim materials | $50-$100 |
| Labor (cut, frame, install, trim) | $200-$500 |
| Total per transom | $300-$800 |
For multiple transoms in the same home, the per-unit cost drops because setup and trim matching are done once. We frequently do 3-5 transoms in a single visit during hallway renovations.
Transoms in Toronto Condos
Condo renovations have one constraint: you typically can't modify exterior walls or windows (those are common elements). But interior walls are yours. A transom above a den or second bedroom door is one of the most cost-effective ways to bring light into a windowless room in a Toronto condo.
Condo board note: Most condo boards don't require approval for interior-only modifications that don't affect structure, plumbing, or HVAC. A glass transom above an interior door falls into this category. Check your condo declaration to be sure.
Frequently Asked Questions
Do interior transoms need tempered glass?
Only if the bottom edge of the glass is within 500mm of the floor, which is rare for transoms mounted above doors. Most interior transoms are 7+ feet above the floor and can use standard annealed glass. We default to tempered anyway for safety.
Can you install a transom above an existing door without rebuilding the wall?
Yes, in most cases. If there's drywall above the door header, we cut an opening, frame it with matching trim, and install the glass. The existing header usually provides enough structural support.
Will a glass transom reduce sound privacy between rooms?
Standard single-pane glass transmits more sound than drywall. For home offices or bedrooms where sound privacy matters, use laminated glass — it cuts noise transmission by 30-50% compared to regular glass.
What glass pattern is best for interior transoms?
Reeded glass is the most popular choice in 2026 Toronto renovations. It lets 80% of light through while fully obscuring detail. Frosted is second. Clear works for hallways where privacy isn't needed.
Can a transom window be operable for ventilation?
Yes. Awning-style transom windows hinge at the top and tilt outward, allowing air circulation between rooms. These are more common above exterior doors but work for interior applications too.
Want to add transoms to your home? We'll come measure the doors, show you glass samples, and handle the full install — cut, frame, glass, trim, paint. Book a consultation and let's bring some light into those dark hallways.