Deadbolt Installation in Larchmont: Grades, Throw, Strikes
A good deadbolt installation comes down to three things: an ANSI/BHMA Grade 1 or Grade 2 deadbolt, a bolt that throws a full inch into the door frame, and a strike plate held by screws long enough to reach the framing behind the jamb. Get those right and the lock is rarely the weak point. In the older houses of Larchmont and Mamaroneck, the weak point is usually the frame, so most of the real work happens there.
What the grades mean
Deadbolts sold in the United States are graded under standards from ANSI (the American National Standards Institute) and BHMA (the Builders Hardware Manufacturers Association). The grade is printed on the packaging, and if it is not, assume the lock was never graded.
- Grade 1 is the top grade. These locks are tested for the most open-and-close cycles and the strongest resistance to prying, impact and bolt pressure. They are built for commercial doors, and they are the right choice for a front door that takes a beating.
- Grade 2 is solid residential quality. For most house doors with a good frame, a Grade 2 deadbolt is enough.
- Grade 3 is the basic level. It is better than nothing, and it is what you find in many builder-grade packs at the big-box store.
Two things the grade does not tell you. It says nothing about how hard the cylinder is to pick or how well the key is controlled. That is the territory of high-security locks. And it says nothing about the door or frame the lock is screwed into. A Grade 1 deadbolt in a split jamb with short screws is a Grade 3 installation.
Bolt throw: the full inch
The bolt throw is how far the bolt extends out of the door edge when you lock it. Look for a one-inch throw. Most decent deadbolts have one, but a full-length bolt only helps if it has somewhere to go.
Here is the common failure. The bolt is an inch long, but the hole drilled into the jamb behind the strike plate is shallow, or it hits an old nail or a gap between the jamb and the stud. The bolt stops halfway. Many deadbolts only lock firmly in place, so the bolt cannot be pushed back in, when they are fully extended. A bolt that stops short can sometimes be pushed back with a blade, which defeats the point.
A quick check you can do yourself: open the door, turn the key or thumbturn, and see whether the bolt comes all the way out. Then close the door and lock it. If the key turns harder with the door closed, or the bolt will not go all the way, the hole in the jamb is too shallow or out of line.
The strike plate and the screws
When a door is kicked in, the lock usually holds. The wood around the strike gives way. The strike plate on many installed deadbolts is fastened with short screws, often around three-quarters of an inch, that only reach the thin jamb trim. One firm kick splits it.
The fix is simple and cheap in parts:
- Use long screws in the strike. Screws around three inches long pass through the jamb and the gap behind it into the wall framing. That changes what a kick has to break.
- Use a reinforced strike. A heavier strike plate, or a box strike that lines the hole the bolt goes into, spreads the force over more wood.
- Do the hinges too. On an out-swinging or weak door, the hinge side is the other half of the equation. One long screw in each hinge, into the framing, helps it resist the same kick.
Shim the jamb before you drive long screws in. Tightening a three-inch screw into a gap with no shim will pull the jamb toward the stud and bend the frame out of line, and then the bolt binds.
Older doors in Larchmont and Mamaroneck
Many houses in Larchmont, and plenty in Mamaroneck, are older Tudors and colonials. Their doors have a history, and a new deadbolt has to fit into it.
Mortise locks already in the door
A lot of older front doors still carry a mortise lock: a rectangular lock body set into a pocket in the edge of the door, often with the latch and a deadbolt in one case. Drilling a new round hole for a modern tubular deadbolt can cut into that pocket. Sometimes the right answer is to repair the mortise lock, sometimes to replace it with a new mortise lock that fits the same pocket, and sometimes to add a separate deadbolt above it where the wood is solid. Look at the door edge before anything else.
Old holes and patched wood
Older doors often carry the ghosts of earlier locks: filled holes, a strike recess that was moved, a patch where a rim lock used to sit. A deadbolt screwed into filler instead of solid wood will not hold. A wrap-around reinforcement plate or a careful wood repair comes first.
Frames that have moved
Houses settle. A door that was square decades ago may now rub at the top or sag at the latch side. A bolt that lines up with the strike on a dry day may miss it on a humid one. Fixing the hinges and the strike position is part of the installation, not an extra.
Salt air near the harbour
On the Mamaroneck waterfront and the streets near Harbor Island Park, salt air works on exterior cylinders. Choose a finish meant for exterior use, and lubricate the cylinder once in a while with a lubricant made for locks, not household oil, which collects grit. The Mamaroneck locksmith page has more on waterfront locks, and the Larchmont locksmith page covers the village side.
Single or double cylinder
A single-cylinder deadbolt has a key outside and a thumbturn inside. A double-cylinder deadbolt needs a key on both sides. People consider the double kind when there is glass near the lock, so a burglar cannot break a pane and reach the thumbturn.
The trade-off is getting out in a fire. A deadbolt that needs a key inside is a real danger if the key is not where you left it, in the dark, with smoke in the hall. Rules on keyed-inside locks vary, so ask your village building department before you fit one. Laminated glass or security film in the door panes deals with the reach-through problem without trapping anyone inside.
Keys, rekeying and the rest of the house
A new deadbolt comes with its own key. If you want it to match the other doors, ask for it to be keyed alike with the locks you already have, or have the whole house rekeyed to one new key at the same time. If you have just moved in, that second option is worth doing anyway, since you do not know how many keys to the old locks are out there. The choice between the two is laid out in our guide to rekeying versus replacing locks.
If a keypad or app is on your list, a smart deadbolt is also an option, with the same rules about throw, strike and screws. Older doors bring their own fitting questions, covered in the post on smart locks for older Tudor and colonial doors.
Doing it yourself or calling a locksmith
Swapping a deadbolt into existing holes of the same size is a reasonable weekend job. Standard deadbolts fit a 2-1/8 inch hole through the door face and a 1 inch hole in the edge, set back 2-3/8 or 2-3/4 inches from the edge. If your old lock used those sizes, a new one will usually drop in.
A new installation on an older door is where it gets harder: boring a clean hole through thick old wood without splitting the edge, working around an existing mortise pocket, deepening and aligning the strike, and shimming and screwing into a frame that has moved. Larchmont Locksmith NY installs, repairs and replaces deadbolts as part of our residential lock service, and two of our technicians live in Larchmont, next door to Mamaroneck.
Frequently asked questions
What grade of deadbolt should I buy?
Grade 1 for a front or back door that sees heavy use or faces the street. Grade 2 is fine for most other house doors with a good frame. Avoid Grade 3 on any exterior door you rely on.
Can I add a deadbolt to an old door that has a mortise lock?
Usually, yes, but not in every spot. The new hole must miss the mortise pocket and land in solid wood. On some doors, repairing or replacing the mortise lock itself is the better answer.
How long should the strike plate screws be?
Long enough to reach the wall framing behind the jamb, which usually means around three inches. Shim the gap first so the screws do not pull the frame out of line.
Is a knob lock alone enough on a front door?
No. The spring latch on a knob lock can often be slipped or forced, and it does not lock in place the way a deadbolt does. A knob lock should be paired with a deadbolt on every exterior door.
For a deadbolt installed properly on an older Larchmont or Mamaroneck door, call Larchmont Locksmith NY at (914) 255-6611.
