How to Fit a Door Chain and Spyhole Viewer

Fit a door chain and a wide-angle door viewer on a UK front door, with positions, fixings, security tips for vulnerable people and when to ask a joiner or locksmith.

A chain and a viewer let you see who is on the doorstep and speak to them without opening the door fully. For older residents, people living alone and anyone who gets unexpected callers, they are some of the cheapest and most useful security fittings available. Both are simple to install, though details like fixings and door thickness matter.

What each one does

Door chain. A short chain that lets the door open a few centimetres. It is not a lock and will not stop a determined intruder, but it prevents a casual push in.
Door viewer (spyhole). A small lens through the door that lets you see outside. Wide-angle ones show a broader view, and digital ones have a small screen.
Door restrictor. A stronger alternative to a chain, with a bar or arm that limits opening.

Use them together with a good lock. See how to replace a door lock cylinder for the lock itself.

Check the door

Before you buy, check:

Door material. Solid timber and composite doors are fine. Hollow or thin doors need care. For uPVC, check what is behind the surface.
Door thickness. Viewers are sold for a range of door thicknesses, commonly 35 to 55 mm. Measure the door.
Frame. The chain needs a solid frame to take force. Rotten or thin timber will fail.
Fire doors. In flats, do not cut holes in fire doors without specific fire-rated products; ask a competent person.

Fitting a door viewer

Choose the height. Typically about 1.5 metres from the floor, but adjust for the people who live there. Wheelchair users or shorter residents might prefer a lower height or an additional viewer.
Mark the position. Centre the viewer in the width of the door and avoid panels or glazing bars.
Drill the hole. Use the diameter specified for the viewer, usually 12 to 14 mm. Start with a small pilot hole from one side, then finish from the other to avoid splintering the face of the door.
Insert the viewer. Push the outer part through from outside and screw the inner part from inside until snug.
Check the view. Look through it from inside, and adjust the length if the lens is not flush.

Fitting a door chain

Mark the chain position. Typically fixed at about shoulder height, to the door and frame. Make sure there is clearance when the door opens fully.
Fix the track to the door. Use the screws provided, ideally long enough to bite into solid timber. For heavier-duty versions, use longer screws.
Fix the receiver or bolt to the frame. Align it with the chain when the door is closed, ensuring the chain is not under tension.
Test. Slide the chain, open the door to the limit, and close the door. Check that it can be released easily with the door closed.

Making it more secure

Use longer screws (at least 30 to 40 mm) into the frame, where possible, to resist forced entry.
Choose a heavy-duty chain or a restrictor with a robust fixing.
Do not rely on a chain as a lock. Keep the door locked as normal.
Consider a letterbox restrictor and a lock that meets modern standards. See how to fit a letterbox.

Safety and vulnerable residents

Make sure that people in the home can release the chain quickly in an emergency, including carers, family or emergency services if needed. For some people, an intercom or video doorbell may be more practical. If you or a relative are worried about doorstep callers, ask local services about advice and consider setting a rule never to let people in unannounced, even if they claim to be from a utility or council.

Common mistakes

Fixing into thin or rotten timber
Drilling too large a hole
Using a viewer designed for a different door thickness
Placing the chain too high or low to use easily
Relying on the chain as the main security

Costs and help

Both fittings are small jobs, which combine well with other tasks; see how to save money by batching handyman jobs. On Compito, you can send a request with your postcode, compare offers from ID-verified local providers, ask questions by message and pay online when you accept. If you are arranging help for a relative, mention access arrangements clearly in the request.

Frequently asked questions

Does a door chain make a door secure?

It adds a layer of caution at the door but does not stop a forced entry. A good lock is still essential.

Can I fit a viewer in a glass door?

Not usually. If the door has glazing, look at other options such as an intercom, video doorbell or a security film.

What height should a viewer be?

Around 1.5 metres is common, but fit it at a height that suits the people who will use it.

Find handyman providers near you

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