Strike plate reinforcement

Strike plate reinforcement is a low-cost modification to a hinged door that increases its resistance to being forced open, by transferring load from the door frame's thin jamb into the structural stud behind it.

On a typical residential door, the deadbolt itself is rarely what fails under a kick. The bolt is steel and the bolt housing is steel. What fails is the softwood jamb around the hole the bolt enters. Most factory strike plates are thin stamped steel held by two screws roughly 19 mm (¾ in) long. Those screws bite only into the jamb, which is commonly a 19 mm board nailed to a stud with an air gap behind it. A forced door therefore splits the jamb along the grain, and the whole plate leaves with a piece of timber attached.

Upgrading the lock does not address this. A higher-grade deadbolt fitted into the same jamb fails in the same place.

• Box strike or heavy-duty strike plate, preferably a "high security" pattern with four screw holes and a formed box behind the bolt hole
• Four 75 mm (3 in) wood screws
• Drill, bit for pilot holes, chisel, tape measure
• Optional: a jamb reinforcement kit — a steel channel, typically 900–1200 mm long, that spans the lock area and distributes load over several studs

1. Remove the existing strike plate and check the bolt's travel. The bolt should throw fully into the hole without contact. If it rubs, correct the alignment first, since a bolt that is not fully thrown is not doing its job whatever the plate is made of.
2. Deepen the mortise if the new plate is thicker, so it seats flush. A proud plate holds the door off its stop and prevents full closure.
3. Enlarge the bolt pocket behind the plate if the new strike has a box. The box stops the bolt from chewing sideways into the timber.
4. Drill pilot holes angled very slightly toward the centre of the wall so the long screws bite the stud rather than skimming past it. Softwood splits if pilot holes are skipped.
5. Drive the 75 mm screws. They should meet firm resistance as they enter the stud. A screw that spins freely at depth has missed and should be backed out and re-angled.
6. Repeat for the latch strike, and use at least one long screw in each hinge leaf. Hinges fail the same way and for the same reason.

• This modification concerns forced entry only. It does nothing about a door being opened with a key, a bypassed cylinder, or an unlocked window.
• On a steel frame, long screws are irrelevant — the load path is already structural.
• Doors hung with a large gap between door edge and jamb remain vulnerable to being spread regardless of the strike, because the bolt has less engagement to begin with. Measure the bolt's actual engagement depth before assuming the door is secure.
• A hollow-core interior door fitted with an excellent lock is still a hollow-core door.

• Door hardware grading (ANSI/BHMA)
• Deadbolt

Practitioner note: alignment problems caused by seasonal frame movement are common in dry, high-diurnal-range climates, and are usually corrected by repositioning the strike rather than replacing hardware — a point made by a locksmith in Fort Collins, Colorado, where frames move noticeably between seasons.