Deadbolt Installation
Two identical deadbolts, one fitted well and one fitted badly, are not the same product.
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A deadbolt differs from a latch in one respect that decides everything else: it has no spring. It goes where it is put and stays there, and it seats in a pocket rather than riding up a ramped keeper. That is the whole reason a latch can be persuaded to move and a properly seated bolt cannot.
Nearly all of the security you are buying is settled by things the packaging never discusses. How far the bolt actually travels once it is fitted, what it lands in at the far end, and whether the strike is screwed to the thin lining of the frame or into the structural timber standing behind it. The lock on the shelf is only half of what arrives at the door.
What decides how well it will hold
- How far the bolt really throws. A bolt catalogued at an inch that only travels two thirds of that once installed, because the bore is shallow or the strike sits proud, has given away most of its advantage. This is measured on the door, not read off the box.
- What the bolt lands in. A thin pressed plate over a shallow chisel pocket is a very different endpoint from a box strike with a steel cup that surrounds the bolt on every side and spreads the load into the frame.
- Screw length, again. Screws long enough to pass through the jamb and bite into the framing behind it change the failure point of the entire door. It is the smallest item on any locksmith's invoice and the one that does the most work.
- How the door is built. Solid and engineered slabs carry the load across the full thickness. A hollow core door is a thin skin over a light internal frame, and the bolt is only ever as strong as the small block of timber around the bore.
- Single or double cylinder. A double cylinder needs a key on the inside as well, which stops an arm reaching through broken glass and also stops you leaving quickly in the dark. That trade-off is a real decision, it is not always permitted, and it should never be made casually.
Have this ready
- The thickness of the door, and whether it is solid or hollow, if you happen to know.
- Whether a bore for a deadbolt already exists, or the door is undrilled.
- Whether there is glass within arm's reach of where the inside thumbturn would sit.
- Whether you want it keyed to match the existing handle set or any other door in the house.
- Whether the door is a fire door or a shared entrance, because that restricts what may be fitted.
If the door already has a deadbolt and you simply want a different one on it, in another finish, another grade or another key, that is a change rather than an installation. see lock change.
Common questions
How many deadbolts does one door need?
One, fitted properly, on each exterior door. A second bolt above the first is uncommon on a house and usually buys less than spending the same effort on the strike, the screws and the frame around the bolt you already have. Doubling the hardware does not double a weak jamb.
Should I fit a double-cylinder deadbolt?
Only with your eyes open. It removes the reach-through risk on a glazed door, and it also means nobody gets out without finding a key, which is a genuine hazard in smoke or in the dark. Local rules restrict it in some situations, and laminated glazing often answers the original worry without the trade-off.
Can a deadbolt be added to a door that has never had one?
Usually. The face is bored for the cylinder and the edge for the bolt, using a jig so the two bores meet squarely, then the strike is cut into the jamb to match. Metal and fibreglass doors can be bored too, though they take longer and their internal construction decides how much support the bolt ends up with.
Will a new deadbolt work with my current key?
Frequently, by rekeying the new cylinder to the key you already use, provided the keyway is compatible. It is worth asking for, because carrying one key is the difference between locking every door every time and locking only the one whose key you can be bothered to find.
Related locksmith services
Describe the lock or key problem
A short description of what happened gets the right tools out for the job.
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