How do I make patio and French doors secure?

Patio and French doors are wide, out of sight at the back of the house, and often the only opening in the house with two moving leaves and a lot of glass. None of that makes them insecure by itself — but they are the doors most often left on a first-floor-style single lock point, and the passive leaf on French doors is very commonly not shot home at all.

Safety

What you'll need

• Sash jammers or surface-mounted locks, two to four
• Anti-lift blocks or track packing for sliders (optional)
• Drill and self-tapping screws for uPVC or aluminium
• A helper for the glazing check (optional)

Step by step

1. On French doors, find and use the shoot bolts.The passive leaf is held by bolts that throw into the head and the cill. On many doors these are never fully engaged, so the pair is held by the lock alone. Lift, throw both bolts fully home, then lock the active leaf.
2. Check the shoot bolts actually engage something solid.Open the passive leaf and look at the holes they enter. A shallow hole in a plastic cill packer is not the same as a bolt entering a steel keep. If there is no proper keep, that is the first thing to fix.
3. Add sash jammers where the leaves meet.A simple pivoting arm screwed to the frame that swings across and blocks the leaf. Fitted top and bottom on the passive leaf, they add two independent restraints for very little money and no specialist skill.
4. Fit them into the reinforced part of the profile.Most uPVC frames carry a steel or aluminium insert. Screwing into plastic alone gives almost nothing. Feel for the insert with a small pilot hole or a magnet, and use the screws supplied for that thickness.
5. On a sliding door, check it cannot be lifted.With the door locked, try to lift the moving leaf upwards in its track. If there is enough vertical play to raise it clear, fit anti-lift blocks in the head track or adjust the rollers so the clearance is minimal. This is the classic sliding-door weakness.
6. Add a secondary lock to a slider.A track blocker, a keyed patio bolt through both frames, or a bar. It gives a second point away from the handle so the whole door is not relying on one latch.
7. Look at the glazing beads.On older units the beads are outside. Internally beaded units are far better; if yours are external, security glazing tape or a laminated pane is the practical answer rather than trying to change the door.
8. Consider laminated glass in the pane nearest the handle.Laminated glass holds together and takes real, noisy, sustained effort to get through, which is the opposite of what an opportunist wants. A glazier can usually replace a single unit within an existing frame.
9. Keep the keys accessible but not visible.Everyone in the house needs to know where the key is, in the dark, in a fire. Nowhere on the door, nowhere visible through the glass, and always the same place.
10. Clear the approach.Bins, a ladder, garden furniture or a wheelie bin left near a patio door are climbing aids and cover. Moving them is free.

Tips

• Test the whole thing at night from outside with the lights on inside. You will see immediately whether the doors look locked and whether valuables are on display.
• Sash jammers are visible from outside, which is part of their value — they are a clear sign that this door will take time.
• If the doors do not lock without a hard shove, fix the alignment. A door that fights back is a door that gets left on the latch.

Common mistakes

• Locking the handle but leaving the passive leaf bolts half thrown — The two leaves then rely on the lock between them alone, and the passive leaf can move. Fully engaging the shoot bolts is free and it is the single most important step on French doors.
• Screwing security hardware into unreinforced uPVC — Plastic alone holds a screw with very little force. The fixing has to bite into the steel reinforcement inside the profile to be worth anything.

If it doesn't work

Questions people ask