No deadbolt, just a knob: your smart lock options

Plenty of American doors have exactly one hole drilled through them. The door from the garage into the kitchen. The back door on a 1960s ranch that was hung before deadbolts became standard practice. There is a knob or a lever at waist height and, above it, nothing but paint.

That door can still take a code instead of a key. What it cannot take is most of the hardware written up on smart lock sites, because nearly all of it is either a deadbolt or something that clamps onto one. So this is about what is left: what a keypad knob or lever actually secures, and how to tell in five minutes whether the thing in your cart will bolt on at all.

Why the door only got one hole

Builders drill what the door schedule tells them to drill, and for decades the schedule said one bore for anything that was not the front door. A bored knob or lever set needs a single 2-1/8 inch hole through the face and a 1 inch hole into the edge. A deadbolt means a second pair of holes, a second piece of hardware and a second strike chiseled into the jamb. Across forty openings, that adds up.

Garage-to-house doors get treated as interior doors even though they open onto a space with a large powered door in it. Older exterior doors often predate the habit of specifying a deadbolt at all, and some carry a plugged hole where a rim lock or a night latch used to sit. None of which says much about the door itself. A solid slab with one bore is still a solid slab.

What a keypad knob or lever actually secures

The bolt is the whole difference. A bored knob or lever throws a spring latch: a beveled tongue with about half an inch of projection, pushed out by a spring and shaped to retract when the door closes against the strike. A deadbolt throws a solid bolt roughly an inch deep that does not move under pressure. No amount of electronics on the outer trim changes which of the two is in your door edge.

A spring latch can be shimmed back if the bevel faces outward and the gap at the jamb is generous. It also puts every ounce of resistance to a shove into a strike plate held by two short screws in soft jamb trim. Swapping those for three inch screws that reach framing does more for the door than doubling the price of the lock.

Grading works differently too. BHMA rates bored locksets on their own scale, separately from deadbolts, so a well-made keypad lever can carry a respectable grade and still be a latch. Read how ANSI/BHMA grades are assigned before treating the numbers on two packages as one ladder.

None of which makes a keypad lever pointless. On a garage door, a basement door or a back door inside a fenced yard, what you want is a code instead of a key with a sensible barrier behind it. Worth knowing which of the two you bought, that is all.

What to measure before you buy anything

Take these off the door first. Each one takes a minute, and any of them on its own can rule a product out.

• Cross bore diameter. Measure the round hole through the door face. Current bored hardware wants 2-1/8 inches, while doors from the 1950s and earlier often have a smaller one, commonly 1-1/2 inches, which no modern keypad lever will fill.
• Backset. Measure from the edge of the door to the center of that bore. It will be close to 2-3/8 or 2-3/4 inches. Mechanical sets usually ship with an adjustable latch covering both. Electronic ones do not always.
• Edge bore and latch face. The hole in the door edge is normally 1 inch. Look at how the latch is finished: a rectangular faceplate with two screws, or a round drive-in collar with none. Replacements come both ways, and the shallow mortise left by a faceplate shows if you switch to a drive-in.
• Door thickness. Interior slabs are commonly 1-3/8 inches, exterior doors 1-3/4. Electronic levers carry batteries and a motor in the interior housing, so each model states a supported range, and a garage door built as an interior slab can sit below it.

Write the four numbers down. Manufacturers publish all of them, usually in a specifications tab a long way below the marketing copy.

What is actually sold for a single bore

Three kinds of hardware fit a knob bore. One popular kind does not, and that is the part people discover late.

Mechanical pushbutton sets

No batteries, no app, no schedule. A row of buttons drives a clutch inside the lever, there is one code, and changing it means opening the lock body and moving pins. They turn up on commercial side doors and pool gates, indifferent to cold and running for years on nothing.

Electronic keypad levers

Schlage, Kwikset and Yale all build bored keypad levers, and they behave like their deadbolt siblings: several user codes, a programming code, auto-lock after a set delay, a low battery warning, and usually four AA alkaline cells in the interior housing. Most run entirely offline with no app involved, which suits a garage door nobody needs to open from the office.

Connected levers

Fewer models, most of them Bluetooth only, with Wi-Fi arriving through a separate plug-in bridge where the maker sells one. Expect to pay more than for the equivalent deadbolt from the same brand.

The category that will not fit

Interior-only retrofits, the August and SwitchBot style devices, clamp over an existing deadbolt thumbturn and turn it with a motor. A door with no deadbolt has no thumbturn, so there is nothing for them to grip, and the same goes for every model advertised as keeping your existing key. If your door does have both bores already and you are only choosing between body styles, the comparison of deadbolts, levers and handlesets is the page you want instead.

Swapping the knob: handing, thickness and the garage caveat

A knob is symmetrical and does not care which way the door swings. A lever is not. Some electronic levers reverse in the field by loosening a screw and rotating the handle, others are sold as left-hand or right-hand items. Stand outside the door: hinges on your right and the door opening away from you makes it a right-hand door. Check that against the model before ordering.

The garage door deserves its own caution. In many jurisdictions the door between an attached garage and the dwelling has to be part of a rated assembly, sometimes with a self-closing device, and altering a labeled door can affect its listing. Ask your local building department what applies rather than taking a rule from a website. There is a practical trap alongside the code one: a self-closing door plus auto-lock leaves you standing in the garage with the door shut, so keep a code on that side. Past those points the swap is an ordinary bored-set job, the same sequence covered in the smart lock installation walkthrough.

Or cut a second bore and add a deadbolt

If this is a main entry you genuinely want secured, the honest answer is often to drill. A deadbolt above the existing latch gives the opening the inch of solid bolt it never had, and it opens the whole smart deadbolt market rather than the short shelf of bored electronic levers.

It is also permanent. The work is a self-centering jig, a 2-1/8 inch hole saw, a 1 inch bit for the edge and a sharp chisel for the strike mortise, and a bore drilled off center cannot be taken back. Read what is involved in adding a deadbolt bore to a door before deciding. Renters should stop here and read the lease, because this is precisely the alteration most leases have a clause about.

Doors that should not be drilled

• Hollow core slabs. There is a solid lock block behind the knob bore and usually nothing above it, so a deadbolt ends up screwed into cardboard honeycomb.
• Insulated steel and fiberglass doors. Many have a wood block only at latch height. Some makers sell a reinforcement kit for a second bore and others say the door will not take one, and their literature settles it rather than the hole saw.
• Fire-rated doors. The label on the hinge edge is part of what makes the assembly rated, and cutting into the slab can void it. Check locally before touching one.
• Doors with glass or a narrow stile near the lock. A 2-1/8 inch hole needs solid material either side of it, and a divided-light door frequently has none to spare.

Common questions

Can I put a smart lock on a door with no deadbolt?

Yes, provided you buy a bored lockset rather than a deadbolt or a retrofit. Keypad levers, and less commonly keypad knobs, are made for exactly that hole. What you cannot do is add app control without replacing the hardware, since every interior-only retrofit needs a thumbturn to grip.

Is a keypad knob secure enough for a front door?

Depends on what else is protecting the opening, and the manufacturers are fairly clear about the split: latch sets are sold as access control, deadbolts as the security element. On a main entry with nothing else on it, most people end up wanting the bolt. Behind a locked gate, or inside a locked garage, a lever on its own is a reasonable call.

Will a keypad lever fit a 1950s door?

Often, but measure the bore first. Tubular hardware standardized on 2-1/8 inches decades ago, and older doors turn up with smaller holes. Enlarging one is a hole saw and a jig away, which puts you back in drilling territory.

Do I need to change the strike plate as well?

A new lockset arrives with its own, and fitting it is worth the five minutes, since the old one may not match the new latch height or faceplate shape. Use the longest screws that reach framing rather than the short ones in the bag.

The short version

A door with one bore takes a bored lockset: a mechanical pushbutton lever, an electronic keypad lever, or one of the few connected levers. Retrofit units are out, since they need a deadbolt thumbturn to hold on to. Measure the cross bore, the backset, the edge bore and the door thickness first, and remember that a latch stays a latch however clever the keypad in front of it is. If the door is a main entry and you want real resistance there, cutting a second bore for a deadbolt is the better spend, and the one job on this page you cannot undo.