Fit a Deadbolt Properly

Before you start

• Take the six measurements on the measurements page and check them against the manufacturer specification sheet for the exact model, not the listing bullets.
• Decide single cylinder or double cylinder before ordering, and read the escape routes page first if you are considering double.
• If you rent, this job changes the door permanently and needs the landlord’s agreement in writing.
• Check whether the door is fire-rated. Boring a rated door can void the rating it was certified with.

The job

1. Dry-fit everything before committingAssemble the lock loosely in the existing holes and see whether it sits square, covers the old marks and closes without fouling the frame. This is the last moment where a wrong purchase costs nothing but a trip to the post office.
2. Fit the bolt assembly and check the throwWith the bolt assembly in the door edge and the door open, throw the bolt fully and measure how far it projects. That projection is what has to land inside the frame. If the bolt only throws part of its travel, something is binding and no amount of tightening the outside plate will fix it.
3. Mark the strike from the bolt, with the door closedClose the door and mark where the bolt actually meets the frame by extending it against the jamb — lipstick, chalk or a pencil in the bolt hole all work. Marking the strike from a tape measure assumes the door hangs square in its frame, and most do not.
4. Cut the strike pocket deep enoughThe pocket in the frame has to accept the whole bolt, not the tip of it. A shallow pocket is the most common reason a deadbolt does not fully engage, and it is invisible once the plate is on. Chisel or drill until the bolt drops in freely with the door closed.
5. Anchor the strike into framingUse screws long enough to pass through the jamb board into the framing behind it, exactly as on the strike plate page. Fitting a new deadbolt with the short screws that came in the packet wastes most of what you just paid for.
6. Cycle it fifty times and then check alignment againThrow and retract the bolt with the door closed, repeatedly. It should move with one finger and no lifting of the door. Any resistance now becomes a jammed bolt in six months, when the door has moved with the season.
7. Set up the access sideIf the lock has codes, set them now: a code each for the people who need one, and none of them the year the house was built. If it has an app, secure that account properly, because a connected lock is a door with a login attached to it.

Stop and call somebody if

• The door needs a new bore and it is metal-skinned, fiberglass or a patio slab. Boring those goes wrong quickly and a locksmith is genuinely cheaper.
• The frame has no solid timber where the strike needs to go.
• The door is fire-rated, or you cannot establish that it is not.
• The bolt will not throw fully even with the assembly correctly seated. Something structural is off and drilling more will not find it.

What goes wrong

• Marking the strike position by measurement rather than from the bolt itself.
• Leaving the packet screws in the strike plate after taking the trouble to fit a good lock.
• Choosing a double-cylinder lock for a glazed door without thinking through what it means for getting out.

Where this applies

• The Front Door — The jamb, not the lock: on most homes the strike plate is held by screws that stop inside a thin board nailed to the framing behind it.
• The Back Door — Privacy: a back door is usually the only approach to the house where somebody can work unobserved for as long as they like.
• The Garage Side Door — Specification: the side door is almost always the cheapest door on the property, with the cheapest lock, and on an attached garage it opens into the house.

Hardware this job may need

• Deadbolts & Keypad Locks — controlling who has a key, and what happens when the battery dies
• Door Reinforcement Locks & Bars — buying time at the door, without blocking the way out

Sources

• Builders Hardware Manufacturers Association — standards for builders hardware
• National Fire Protection Association — home fire safety and escape planning
• International Code Council — model building codes and adoption