Secondary Glazing for Patio Doors and French Doors: Options, Safety and Access

Patio doors and French doors are often the coldest and noisiest part of a room. They are large, they are frequently single-glazed in older homes, and the meeting stiles between the leaves let draughts straight in. Many people assume secondary glazing only works on windows, but secondary glazing for patio doors and French doors is entirely possible, as long as it is designed around one thing: you still need to walk through the door.

The Main Options

1. Horizontal sliding secondary doors

The most common solution for wide openings. Two or more panels slide past each other on a low-profile track, so you can open one side to step through. This is the natural choice behind sliding patio doors, and it works well behind French doors where there is enough reveal depth. Read more in our guide to horizontal sliding secondary glazing.

2. Hinged secondary doors

A pair of hinged inner leaves that mirror the French doors outside. They open into the room, so you need clear floor space for the swing. Hinged units give the widest clear opening and look the most like a traditional inner door. See our hinged secondary glazing guide.

3. Fixed side panels with an opening centre

Where French doors have fixed side lights, those can take fixed secondary panes, with sliding or hinged panels only across the doorway itself. This keeps costs down and gives the slimmest sightlines on the parts you do not open.

4. Lift-out panels for doors you rarely use

If the doors only open in summer, lift-out secondary glazing can be fitted for the colder months and stored away when the weather turns.

Safety Glass Is a Must

Glazing in and around doors is a critical location under Building Regulations. Any glass in a door, or within 300mm of a door and below 1500mm from the floor, should be safety glass that breaks safely, either toughened or laminated. For secondary glazing on patio and French doors, we use toughened or laminated glass as standard. Laminated acoustic glass meets the safety requirement and reduces noise at the same time. See our guide to secondary glazing and building regulations for more.

Thresholds and Trip Hazards

The bottom track of a sliding unit needs careful design. We use low-profile tracks, often recessed or ramped, so the step through stays safe. Hinged units can avoid a bottom track entirely, which is one reason they suit doors used every day.

Noise and Heat Benefits

A doorway has a large glass area, so the improvement is noticeable. A sealed secondary door with a good air gap cuts draughts around the meeting stiles, reduces heat loss through the glass, and can greatly reduce noise from a garden that backs onto a road or railway. For the noise side, see our acoustic secondary glazing page.

What It Costs

Because doorways are large and need safety glass and heavier hardware, they cost more than a typical window. As a guide, expect roughly £1,200–£3,000 per doorway depending on width, opening style and glass. Our cost guide shows current London prices for standard windows.

Things to Check Before You Order

• Reveal depth: Is there room inside the frame for the new unit, or will it need to be face-fixed to the wall?
• Handles: Will the outer door handles clash with the inner unit? We check this at survey.
• Swing space: For hinged inner doors, is there clear floor space for them to open?
• Daily use: Doors used every day suit hinged or sliding units; lift-out panels only suit doors used occasionally.
• Escape routes: If the door is a means of escape, the inner unit must open easily without a key.

For an overview of every opening style, see our types of secondary glazing page. To get a design for your doors, book a free survey.

Frequently Asked Questions

Can you put secondary glazing on French doors?

Yes. Hinged inner leaves or a horizontal sliding unit can be fitted behind French doors so you can still open them and step through.

Can secondary glazing be fitted to sliding patio doors?

Yes. A matching horizontal sliding secondary unit is usually the best solution, with a low-profile track to keep the threshold safe.

Does secondary glazing for doors need safety glass?

Yes. Glass in and next to doors is a critical location and should be toughened or laminated safety glass.