Glass for a door canopy: choosing, replacing, looking after

A door canopy is iron and glass, and the glass counts as much as the iron. It is the glass that lets light into the hall, the glass that gives the piece its texture seen from the pavement, and the glass that one day breaks under a branch or a hailstone.

This guide covers the subject: the types of glass suited to a canopy, their indicative budgets, the method for replacing a broken pane on an existing piece, and the upkeep that avoids nasty surprises.

What the glazing has to do

Three things, in this order. Let the light through: that is the whole point of a glazed canopy, which shelters the threshold without darkening the entrance, unlike a solid canopy in sheet metal or tiles. Survive outdoors: snow, hail, branch strikes, temperature swings. Not injure anyone if it breaks: the glazing is over people’s heads, and that is the criterion that really separates the types of glass.

A fourth criterion, appearance, matters more than people expect: perfectly smooth clear glass shows the underside of the frame, the dust and the rain marks. The textured glasses of period canopies are not a decorative whim: they diffuse the light and hide the dirt between cleans.

The types of glass for a canopy

Textured cathedral glass is the historic glazing of the door canopy: translucent, animated by an irregular texture that diffuses light and blurs the direct view. It is the truest to the 1900 spirit, the glass found on Belle Époque fans and the canopies of the period, whose vocabulary our page on the Art Nouveau door canopy sets out.

Patterned glass is its industrial cousin: a regular motif (stipple, diamonds, drops) rolled into the surface. Less irregular than cathedral glass, it does a comparable job for a slightly lower budget.

Wired glass traps a wire mesh that holds the pieces if it breaks. Very common on period canopies and workshop roof lights, it keeps a definite retro charm. Be aware that it breaks more easily than modern glass: today it is chosen for appearance, in a like-for-like restoration, rather than for safety.

Laminated safety glass bonds two sheets of glass to a plastic interlayer. If it breaks, the pieces stay attached to the interlayer instead of falling: that is the principle that makes it essential over a doorway. It is the glazing we fit as standard on our new canopies, in 44.2 make-up.

Toughened glass is heat-treated to be markedly more resistant to impact and bending. When it does break it fragments into small, blunt pieces — but those pieces fall. On its own it suits vertical glazing; overhead above a doorway it is combined with lamination rather than used alone.

Frosted or sandblasted glass plays the card of privacy and milky light. Watch the maintenance overhead: the frosted face catches dirt, so it goes on the inside.

Polycarbonate: why we advise against it

Polycarbonate has its arguments: it is light, hard to break and cheap. On a utilitarian shelter it holds its own. On a wrought iron canopy, honesty requires saying it: it yellows. UV dulls the material year after year, even with a surface treatment, and the yellowish veil that settles in is irreversible. It also scratches at the least firm clean, and its plastic note under rain has nothing to do with the sound of glass.

The paradox is economic: you save a few tens of euros per square metre on a piece worth several thousand, and you end up replacing the dulled polycarbonate with glass a few years later. Better to fit the right glazing from the start.

Replacing a broken pane on an existing canopy

A broken canopy pane is neither a disaster nor a reason to replace the piece: glazing can be changed, including on a century-old canopy. The method, in order:

1. Make safe and remove. Take the pieces out working from the top, in heavy gloves and goggles, with the threshold sheeted. If the glass is laminated, it comes out in one piece.
2. Identify how it is bedded. Two cases: the glass sits in a rebate (the L-shaped groove in the section) and is held by a bead of putty, the technique of period canopies; or it is clamped by glazing beads, screwed strips that come off and go back on, a more recent and more convenient technique.
3. Take the measurements. Measure the rebate edge to edge, at several points, because old frames are never perfectly regular, then take off a few millimetres of clearance each side: the glass must never touch the metal, which expands differently.
4. Order the glass. From a glazier, cut to size: same type, same thickness as the existing, with a card template for the curved panes of a fan. It is the moment to move to laminated if the pane overhangs the doorway.
5. Refit. Rebate cleaned and repainted if bare metal is exposed, a bed of putty or a new seal, glass set on packers, then a finishing bead or the beads screwed back. Water must be able to escape: putty that blocks the drainage of the rebate is preparing corrosion.

Glass and safety over a doorway

The principle takes one sentence: above a place where someone may be standing, the glazing must stay in place when it breaks. That is exactly what laminated glass does, its interlayer keeping the pieces together, and what neither plain glass nor toughened glass alone will do. For a new canopy above a front door the question hardly arises: laminated, textured if you like the look. The precise requirements depend on the configuration and the use of the building, and they are checked at the study stage with your ironworker or glazier — in the United Kingdom that means the relevant part of the Building Regulations for glazing in overhead positions.

Looking after the glazing

Glass asks for little: soapy water, a squeegee, a rinse, once or twice a year. Three points of vigilance all the same. The seals and putty, to inspect at every clean: a cracked bead lets water sit against the metal. Moss along the bottom edge, to be removed before it holds moisture. And heavy snow, to be brought down with a brush from the ground after a big fall, without climbing on the piece.

Is your project bigger than the glazing? Our canopies are supplied with the glass included, laminated or period-look depending on the model: ask for a free study — a photograph and dimensions are enough.