How do I fit a door chain or viewer safely?

Both are ten-minute jobs, and both are routinely fitted in a way that looks right and holds almost nothing.

Safety

What you'll need

• Drill, and a flat wood bit matching the viewer's barrel
• Bradawl, screwdriver and a pencil
• Longer screws than the ones supplied

Step by step

1. Understand what a chain does and does not do.It lets you open the door a few inches to speak to someone. It will not resist a determined push, and it is only as strong as what the plate is screwed into.
2. Consider a restrictor instead.A door limiter or restrictor bar is substantially stronger than a chain and fitted the same way. If security rather than convenience is the point, it is the better choice.
3. Position the chain about a third up the door.Roughly waist height. Too high and it is awkward; too low and it is easy to force. Keep it clear of the lock and the hinge side.
4. Find the solid timber in the frame.The visible lining is often thin, with a gap behind it before the structural frame. Screws into the lining alone pull out immediately. Probe with a bradawl to find where the solid timber is.
5. Use longer screws than supplied.Supplied screws are typically far too short. Use the longest that will reach solid timber without going through anything — this is the difference between a working chain and a decorative one.
6. Pack behind the plate if there is a void.A hardwood packer filling the gap between the lining and the frame lets the screws bear properly. Without it, the fixing crushes the lining under load.
7. Fit the door plate and the frame plate in the right order.Slide plate on the frame, chain anchor on the door, with the door closed so the alignment is right. Mark through the holes rather than measuring.
8. Check the chain length.It should let the door open just enough to speak and pass a small item, and no more. A long chain gives someone room to get a foot in.
9. Set the viewer at the right height.Eye height of the shortest adult who uses the door, usually 1.4 to 1.5 metres. Fitted for the tallest person, it is useless to everyone else.
10. Drill the viewer hole square.A flat wood bit matching the barrel diameter, held perpendicular to the door face. Angled slightly, the two halves will not meet and the lens will not focus.
11. Drill from both sides to avoid breakout.Go part way from outside until the point breaks through, then finish from inside. Drilling straight through tears the face on the far side.
12. Check the door thickness against the viewer.Viewers come in ranges. Too thick a door and the halves will not screw together; too thin and it stands proud.
13. Choose a wide-angle viewer.A 180 degree lens shows the whole doorstep. A narrow one shows only what is directly in front, which is exactly where someone standing aside will not be.
14. Consider a digital viewer or doorbell camera.For anyone who cannot easily reach a viewer, a screen-based viewer or a video doorbell answers the same need without the height problem.
15. Test both properly.Push firmly against the chained door to check the fixings hold, and look through the viewer at someone standing at the edge of the step.

Tips

• The screws supplied are almost always too short. Longer screws into solid frame timber are the whole job.
• Set the viewer for the shortest person in the house, not the tallest.
• A restrictor bar is far stronger than a chain and fits the same way.

Common mistakes

• Screwing the chain plate into the door lining — The lining is thin board with a void behind it. The screws pull straight out under pressure, so the chain gives reassurance without providing any resistance.
• Drilling the viewer hole straight through in one pass — The bit tears out the face on the far side, leaving a ragged hole the escutcheon may not cover. Drill from both sides instead.

If it doesn't work

Questions people ask