How do I strengthen a wooden front door and its frame?

Almost all the security marketing points at the lock, and almost all the weakness is in what surrounds it. A timber frame is typically a 25mm lining nailed to a rough opening with a void behind, and the striking plate is often held by two 25mm screws into that lining. Fixing that is unglamorous, cheap and permanent.

Safety

What you'll need

• Hinge bolts (dog bolts), two per door
• A door frame reinforcing bar, sized to your frame
• Letterplate cowl or internal restrictor (optional)
• 100mm screws and frame fixings
• Drill, chisel, bradawl

Step by step

1. Test the frame before buying anything.Press firmly on the frame beside the lock. If it flexes, the lining is not fixed back to the masonry there. That flex is the single biggest weakness on most timber doorsets and no lock upgrade compensates for it.
2. Refix the frame into the structure.Drill through the lining beside the lock keep and beside each hinge, into the masonry behind, and fix with long frame fixings. Pack the void behind with hardwood packers before tightening so the frame is not pulled out of square.
3. Replace the striking plate screws with long ones.The plate the latch and deadbolt shoot into is usually held by short screws into the lining alone. Replace with 75-100mm screws that reach solid timber or the packed masonry behind. This one change costs pence.
4. Fit a frame reinforcing bar over the lock area.A London bar sits on the frame face over the keep; a Birmingham bar is let into the rebate. Either spreads load along the frame instead of concentrating it at two screw holes. Fix it with the long screws supplied, into masonry where you can.
5. Fit hinge bolts on the hinge side.A hinge bolt is a fixed steel peg in the door edge that engages a socket in the frame as the door closes. It means the hinge side is held even if the hinges themselves are attacked, and it costs a few pounds a pair.
6. Position the hinge bolts between the hinges.Roughly a third and two-thirds up the hinge stile, clear of the hinges. Drill the door edge, tap the bolt in, then rub chalk on its tip, close the door onto the frame and drill the socket where the chalk marks.
7. Deal with the letterplate.Fit a cowl or an internal restrictor plate. It stops anything being reached or hooked through, and it also cuts the draught. Never leave keys, handbags or car keys anywhere near the door.
8. Look at any glass beside the lock.A glazed panel within arm's reach of the inside handle changes the picture completely. Laminated glass or a well-fitted security film is the answer there, along with a key-operated rather than thumbturn lock — balanced against escape in a fire.
9. Check the door closes and locks without force afterwards.Everything here tightens tolerances. If the door now binds, adjust the keep positions rather than forcing it; a door that is hard to lock ends up not being locked.

Tips

• Do the long screws in the striking plate first. It is five minutes' work and it is the highest-value single change on a timber door.
• Hardwood packers behind the frame matter — tightening a frame fixing into a void just pulls the lining out of shape.
• If the door is a fire door on a flat entrance, check with the building manager before drilling anything. Certification is easily invalidated.

Common mistakes

• Upgrading the lock and leaving the keep alone — The bolt is only ever as strong as what it shoots into. A five-lever deadlock throwing into a plate held by two 25mm screws in a thin lining is limited by the plate, not the lock.
• Fitting a reinforcing bar with the screws in the box — Supplied screws are often short enough to stay in the lining. Use fixings long enough to reach the masonry or the structural frame behind it.

If it doesn't work

Questions people ask