How to Fit a Door Security Chain

Installing a security chain on your front or entrance door is a simple way to strengthen home security and add extra peace of mind.

Follow our guide below to learn the correct way to fit a door chain safely and effectively.

What is a Door Chain?

A door chain is a security device that attaches a chain between a bracket on the door frame and a catch on the door. It lets you open the door slightly to see or speak to visitors while preventing unwanted entry.

Door chains are usually used alongside other security measures, such as a peephole or camera, so you can safely check who is outside before fully opening the door.

While a door chain can resist moderate force, extreme pressure may break the chain or fittings. For this reason, it should always be used with a high-quality lock, such as a 5-lever mortice lock, and never as the sole security measure.

When buying a door chain, choose a strong, corrosion-resistant model. Products tested to TS003 standards or Police Approved carry extra assurance of quality and durability.

Good quality Chubb door chain

Different Types of Door Chains

There are three main types of door chains: standard chains, lockable chains, and chain restrictors. Each type offers different levels of security and is suited to specific situations, with its own benefits and limitations.

Door Chain Restrictor

A door chain restrictor is ideal for UPVC and composite doors, though it can be fitted to any door with an internal handle. Unlike traditional chains, it doesn’t require drilling into the door itself.

One end of the chain attaches to the door frame, while the other end slips over the handle, limiting how far the door can open.

Door chain restrictors are easy to install, effective, and simple to use, making them especially suitable for the elderly or less mobile.

Door restrictor door chain

Standard Door Chain

The standard door chain is the most common type. When installed correctly, it provides reliable additional security and can withstand moderate force.

These chains are inexpensive, easy to use, and relatively simple to install. However, poorly fitted or low-quality chains may fail, so choose a sturdy, well-made product for best results.

Standard door chain

Lockable Door Chain

A lockable door chain offers enhanced security compared to a standard chain. It features a locking mechanism on the bracket, preventing the chain from being removed without unlocking it.

This makes it highly secure and childproof, stopping children from opening the door by sliding the chain. Some models can even be unlocked from the outside by authorised users.

Lockable chains provide stronger protection than standard chains, but in an emergency, they may slightly delay exit from the property.

Locking security door chain

Parts of a Security Door Chain

Door chains are simple devices, but understanding each part ensures correct installation. The main components of a standard security chain are:

• Keep: Attaches the chain to the door.
• Bracket: Secures the chain to the door frame.
• Chain: Connects the keep to the bracket, allowing limited door movement.

The parts of a standard door security chain

Fitting a Door Chain to UPVC or Composite Doors

Yes, door chains can be fitted to most UPVC and composite doors, but the ease and strength of the fix depends on the door’s core material and the screws used.

Composite doors usually have a timber core, making them straightforward to secure firmly once you locate the timber sections. UPVC doors often have a steel-reinforced core, which requires drilling pilot holes and using self-tapping screws for a strong, lasting fix.

Mark all fixing points carefully, drill pilot holes, then attach the chain securely. If this seems complicated, a door chain restrictor is a simpler alternative that avoids drilling into the door itself.

UPVC door frame cross section showing steel core in red

Tips Before Installing a Door Chain

Before fitting a security chain, keep a few key points in mind to ensure a strong, safe and effective installation.

Letter Box Considerations

If your door has a letter box, it is usually cut into the centre cross rail, which weakens that section slightly.

Installing a door chain directly in line with the letter box may reduce its strength. For a more secure fix, position the chain above the letter box where the door material is stronger.

Storing the Chain

Ensure the chain bracket is installed so the chain can hang neatly in its slot when not in use. This keeps it out of the way, preventing it from getting caught between the door and frame and avoiding potential damage.

Most brackets include a built-in storage section (often marked “A”) or a similar feature for keeping the chain safely stowed when not in use.

Common Security Chain Dimensions

Most door chains follow standard dimensions. Ensure you have at least 34mm of door frame visible on the closing side to fit the chain bracket properly.

If your frame is thin or covered by architrave, you may need to cut a small section to mount the bracket. Use a multi-tool with the correct blade or carefully use a hand saw.

Measure the bracket height, mark it on the architrave opposite the keep, cut out the section, smooth with sandpaper, repaint if needed, and then attach the chain bracket securely.

Tools Needed for Installing a Door Chain

To fit a door security chain properly, you will need the following:

• Door chain kit of your choice
• Pen or pencil for marking
• Small spirit level
• Drill or driver
• Pilot drill bits (around 1mm, HSS recommended)
• Self-tapping security screws (required for UPVC doors with steel cores)

How to Fit a Door Security Chain

In this guide, we’ll demonstrate the simple step needed for fitting a standard door security chain on a timber external door.

Regardless of your door type, the process is pretty much the same.

Step 1 – Locate the Strongest Part of the Door

Start by identifying the strongest part of your door. Typically, this is the horizontal lock rail in the centre, designed for mortice locks.

If your door lacks a lock rail, use the vertical uprights (door jambs) instead, they provide a solid, secure fixing point for the chain.

Step 2 – Position the Chain Bracket on the Door Frame

Decide where the main chain keep will go on the door frame. The bracket can be mounted horizontally or vertically, depending on available space.

Place the bracket opposite the top half of the lock rail to avoid the weakened centre near the letterbox. Mark the screw holes for drilling.

Step 3 – Drill and Fix the Chain Bracket

Drill pilot holes for the chain bracket using screws at least 25mm (1 inch) long. Short screws can fail if the door is forced.

For help with pilot holes and countersinking, see our project on Pilot Holes and Countersinking.

Secure the bracket with a screwdriver into the pilot holes. If using a battery screwdriver, take care not to scratch the door reveal. Slightly angling the screws can improve grip, especially on doors where previous screws were too short.

Hang the chain in the bracket slot to keep it out of the way for the next step.

Step 4 – Position the Security Door Chain Keep

Place the security chain keep on the door’s lock rail, directly opposite the chain bracket you installed earlier. Use a spirit level if needed to ensure both fittings line up evenly.

Hook the chain into the bracket and hold the keep in place on the door. Slide the keep slightly towards the centre of the door until the chain is tight but can still be lifted out of the keep when the door is closed.

When set correctly, the chain should allow the door to open slightly (around an inch) so you can speak to a visitor, while still preventing anyone from reaching inside to remove the chain.

As a general guide, the front edge of the keep is usually positioned about 50mm from the edge of the door. Moving the keep closer to the edge will allow the door to open wider when the chain is engaged.

Step 5 – Mark the Keep Fixing Points on the Door

Once you have positioned the keep so the chain works smoothly and the door only opens a small, safe gap, mark its final location.

Hold the keep in place and mark the screw holes with a pencil or pen. Before marking, check that the keep is level using a small spirit level, such as a boat level, to ensure a neat and accurate installation.

Step 6 – Drill Pilot Holes and Fix the Keep to the Door

After checking the keep is level and marking the fixing points, move it aside and drill small pilot holes using a drill/driver.

Position the keep back over the holes and secure it to the door with screws. If the screws supplied with the door chain kit are too short or weak, replace them with stronger, correctly sized screws for a firm and secure fit.

Step 7 – Test the Security Door Chain

Once the keep is fully fixed, place the chain into the slot and carefully open the door.

Ask someone to stand outside and try to remove the chain while the door is slightly open. If the chain and keep have been positioned correctly, it should not be possible to release the chain from outside.

Your door chain is now installed and ready to provide an extra layer of home security, good job!

Fitting a security door chain is a simple but effective way to improve the safety of any entrance door in your home. It allows you to open the door slightly to speak with visitors while still keeping a secure barrier in place, giving you time to react if someone attempts to force entry.