The basics
What a deadbolt does that a knob lock cannot
The name describes it. The bolt does not spring back.
Spring latch versus dead bolt
The lock in most doorknobs uses a spring latch. It has a slanted face so the door can close on its own, and the spring pushes it back out once it passes the strike. That convenience is also its weakness. A spring latch can be pushed back by anything that reaches it, and it usually extends only a short distance into the frame.
A deadbolt has no spring and no slant. The bolt moves only when a key or thumb turn moves it, and once it is extended it cannot be pushed back from the edge of the door. A good residential deadbolt throws its bolt about an inch into the frame, far enough to reach past the door stop and into the jamb behind it.
That does not mean every deadbolt is strong. A deadbolt is one part of a system that includes the door, the frame, the strike plate and the screws that hold it all together. Most forced entries through a locked deadbolt do not break the lock at all. They split the wood of the frame around the strike. That is why installation matters as much as the hardware you choose.
Types
Single cylinder, double cylinder, rim and keyless deadbolts
Deadbolts come in several forms. The right one depends on the door, what surrounds it, who lives in the home, and how the household leaves in an emergency.
Single cylinder deadbolts have a key on the outside and a thumb turn on the inside. They are the most common residential deadbolt, and for good reason. Anyone inside can leave quickly without searching for a key, which matters in a fire or any other emergency.
Double cylinder deadbolts require a key on both sides. People choose them for doors with glass panels close to the lock, reasoning that a burglar who breaks the glass cannot reach in and turn a thumb turn. The trade off is serious. In an emergency, anyone inside needs the key to get out. Many fire safety authorities discourage double cylinder locks on doors used for escape, and some local building codes restrict them. If you are considering one, check with your local code office first, and if you install one, keep the key near the door where every member of the household can find it in the dark. Often a better answer for a door with glass is security film on the glass or a different door.
Rim deadbolts, sometimes called surface mounted or vertical deadbolts, mount on the inside face of the door and lock into a matching keeper on the frame. They are common on older apartment doors and on doors too thin or too damaged for a standard bored deadbolt. A well installed rim lock with a sturdy keeper can be very strong.
Keyless and keypad deadbolts replace the exterior key with a code. Mechanical versions use buttons and no electronics. Electronic versions use batteries and can connect to phones. We cover these on our keypad lock and smart lock pages.
Grades and what they mean
Many deadbolts carry a grade from a standards program run by the builders hardware industry. The grades, commonly listed as 1, 2 and 3, reflect testing for things like how many cycles the lock survives and how much force it withstands. Grade 1 is the most demanding and is common in commercial buildings. Grade 2 is typical of good residential hardware. Grade 3 meets the basic standard. A grade tells you about the lock, not about the door or the frame, so a Grade 1 deadbolt in a weak frame is still limited by the frame.
What we check
Before we install a deadbolt
- Door material and condition. Solid wood, steel, fiberglass and hollow core doors all behave differently. A hollow core interior style door used as an exterior door will not hold a deadbolt well no matter what lock goes on it.
- Existing holes. A replacement deadbolt usually fits the existing bore, but old hardware may have left oversized or misaligned holes. Reinforcement plates or wrap around plates can restore strength around a damaged bore.
- Backset. The distance from the door edge to the center of the lock bore is typically one of two common sizes. Most deadbolts adjust between them. We confirm before drilling or ordering.
- Relationship to the knob. The deadbolt and the knob or lever need enough space between them so neither interferes with the other and so hands do not get pinched.
- Frame and jamb. We look for cracks, previous repairs, loose trim and gaps between the jamb and the wall framing. The strike is only as strong as the wood it is screwed into.
- Door alignment. A door that sags or rubs will push the bolt against the strike. We correct hinge problems before the deadbolt goes in.
- Glass near the lock. Glass within reach of the thumb turn changes the conversation about which deadbolt and which other measures make sense.
How it works
What happens during a deadbolt installation
For a replacement, we remove the old deadbolt, inspect the bore, the edge hole and the strike, and correct anything that is worn or out of line. For a new installation on a door without a deadbolt, we mark the door, bore the face for the lock body and the edge for the bolt, and cut the mortise for the faceplate so it sits flush.
The frame side is where the real work happens. We drill the bolt hole into the jamb deep enough for the bolt to extend fully. A bolt that hits wood before it is fully thrown is not locked the way it should be, and some deadbolts will not even stay locked in that position. Then we install the strike plate, and where the frame allows, a reinforced strike with long screws that pass through the jamb and anchor into the wall framing behind it. Short screws that hold only the thin jamb are the most common weakness in residential doors.
The deadbolt goes in next. We check that the bolt throws and retracts smoothly with the key and with the thumb turn, with the door open and with it closed. We confirm the bolt reaches its full extension into the frame. If the household wants the new deadbolt to match an existing key, we key it to match during the same visit.
Finally, we test everything with the door closed firmly and closed gently, and we show the household how the lock works. If the key or the thumb turn needs any force at all, we adjust until it does not.
Looking after a deadbolt once it is in
A deadbolt needs very little attention, but the little it needs makes a difference over the years. Once or twice a year, lock and unlock it with the door open and watch the bolt. It should move its full distance smoothly and stop firmly at each end. If it hesitates or grinds with the door open, the lock itself needs cleaning or repair. If it moves smoothly with the door open but drags with the door closed, the strike or the door has shifted.
For lubrication, use a dry lubricant made for locks, such as graphite or a dry lock spray, and use it sparingly. Oily sprays attract dust and grit, and over time they turn into a paste inside the cylinder that makes the key harder to turn rather than easier. A small puff into the keyway and a few turns of the key is enough.
Check the screws. The screws holding the interior thumb turn and the strike plate can loosen over time, especially on a door that gets slammed. A loose interior plate lets the lock body shift and puts strain on the tailpiece that connects the cylinder to the bolt. Tighten them gently, since overtightening can bind the mechanism.
Finally, pay attention to the key. A key that has worn smooth at the tips of its cuts can start failing in a lock that is still perfectly fine. Have a new key cut to the lock's original code or to the lock itself rather than copying the worn key, so the wear does not carry forward into every copy.
The frame
Why the strike plate matters more than the lock
The weakest point in most locked doors is a few inches of pine.
A standard strike plate is a small piece of metal held by two short screws that go into the door jamb. The jamb is often a thin board, and behind it is a gap and then the wall framing. When someone kicks a locked door, the bolt pushes against the strike, the short screws pull out of the thin jamb, and the wood splits along the grain. The deadbolt itself is often undamaged.
A reinforced strike changes that. It is larger, often heavier, and it uses long screws that pass through the jamb, cross the gap and bite into the framing behind. The force of a kick is then spread across more wood and anchored in the structure of the house rather than in trim. On many homes this single change does more for security than upgrading the lock.
The hinge side matters too. If the hinges are held by short screws, the door can fail at the hinges instead. Replacing at least one screw in each hinge with a longer one that reaches the framing is a simple improvement. Our door frame security guide covers the full set of frame improvements.
Keying
Matching the new deadbolt to the keys you already use
A new deadbolt comes with its own keys. Most households do not want another key on the ring. There are a few ways to handle that. We can key the new deadbolt to match the existing knob lock or other doors, so one key works everywhere. We can key the whole house to a new key at the same time, which also removes any old keys from circulation. Or, if the household wants separate keys for different doors, we can leave the deadbolt on its own key.
Keying alike depends on the locks sharing a compatible keyway. Many residential brands use common keyways, but not all do. If the existing locks and the new deadbolt use different keyways, we can often choose a deadbolt that matches or change the cylinder. We sort that out before the installation so nobody ends up with a mismatched set.
If the reason for the new deadbolt is that keys have gone missing or the home has changed hands, keying everything to a new key at the same visit makes sense. Our page on lock rekeying explains how that works on the existing hardware.
Choosing
Deadbolt options compared
| Door situation | What usually fits |
|---|---|
| Solid front door, no glass near the lock | A single cylinder deadbolt with a reinforced strike and long screws |
| Door with glass close to the thumb turn | A single cylinder deadbolt plus glass film or door changes, or a double cylinder only after checking local rules and planning emergency exit |
| Older thin door or damaged bore | A rim deadbolt on the inside face, or a reinforcement plate around a bored deadbolt |
| Side door used by many people | A keypad deadbolt so nobody needs to carry a key |
| Rental or apartment door | A deadbolt keyed to the owner's system, with the landlord's approval |
| Garage entry door into the house | A deadbolt with the same care as the front door, since it is often the most exposed entry |
Avoid these
Deadbolt mistakes that weaken a door
- Leaving the bolt short of full extension. A shallow bolt hole in the frame stops the bolt early. The lock feels locked but the bolt barely reaches past the door stop.
- Using only the short screws from the box. The screws that come with many deadbolts are short. Long screws into the framing are where the strength comes from.
- Ignoring a sagging door. If the bolt drags against the strike, people stop using the deadbolt because it is a nuisance. An unused deadbolt protects nothing.
- Choosing a double cylinder without an exit plan. A door that needs a key to leave can trap people in an emergency. Think carefully and check local rules.
- Installing a strong lock on a weak door. A hollow door or a rotted frame limits any lock. Fix the door or frame first.
- Forgetting the garage entry door. Many homes put a good deadbolt on the front door and a basic knob lock on the door from the garage into the house.
Local factors
Deadbolts on Delaware homes
Old row homes, new developments and everything in between.
In older Wilmington row homes, in Elsmere and in parts of New Castle and Dover, we often find thick original wood doors with several generations of holes from previous locks, frames that have shifted, and jambs that have been repaired more than once. These doors can take a strong deadbolt, but they almost always need preparation first.
Newer developments in Middletown, Townsend, Smyrna and around Camden usually have pre-hung doors with standard bores and thin jambs. The lock goes in easily. The weakness is the thin jamb and short screws, which is why reinforced strikes are so often the most useful upgrade in newer homes.
Humidity matters across the state. Wood doors swell in summer, so a deadbolt that throws easily in March can bind in July. We leave the strike opening with enough clearance to handle seasonal movement while still holding the bolt firmly.
Questions
Frequently asked
Can you add a deadbolt to a door that has never had one?
Yes, on most solid exterior doors. We bore the door face and edge, cut the faceplate mortise, drill the bolt hole in the frame and install a strike with long screws. Hollow core doors and badly damaged doors may need attention first, and we will tell you if the door itself is the weak link.
Should I choose a single or double cylinder deadbolt?
For most doors, a single cylinder deadbolt with a thumb turn inside is the safer choice because everyone can leave quickly in an emergency. Double cylinder locks need a key to get out, and some local codes restrict them. If glass near the lock worries you, there are other ways to address it.
Can the new deadbolt use my existing house key?
Usually, if the new deadbolt shares a compatible keyway with your other locks. We can key it to match during the installation, or key the whole house to a new key if old keys are a concern.
What is a reinforced strike plate?
It is a heavier strike that uses long screws to anchor through the door jamb into the wall framing behind it. That spreads the force of a kick into the structure of the house instead of the thin jamb, and it is often the most effective single upgrade for an exterior door.
My deadbolt is hard to lock. Do I need a new one?
Not always. A deadbolt that is hard to throw is often fine inside but dragging on a misaligned strike or hitting a shallow hole in the frame. Adjusting the strike or the door usually fixes it. If the lock is worn internally, repair or replacement is the answer.
What does a deadbolt grade tell me?
Industry grades describe how the lock performed in standardized durability and strength testing, with Grade 1 the most demanding. The grade describes the lock only. The door, frame and strike installation decide how well the whole entry resists force.
Can you install a deadbolt on a metal or fiberglass door?
Yes. Steel and fiberglass doors are bored differently from wood, and some have internal reinforcement where the lock goes. We use the right tools for the material and make sure the lock is fastened securely.
Do rim deadbolts work as well as bored deadbolts?
A good rim deadbolt with a sturdy keeper, properly anchored, can be very strong. It is often the best choice for older thin doors, for doors with damaged bores, and for apartment doors where a surface lock is the norm.
Need a deadbolt installed right?
Call and we will fit the lock, anchor the strike and make sure the bolt throws all the way.