How to childproof casement windows: the crank is the lock, and a toddler can turn a crank

Why a casement is a different problem

A double-hung or horizontal slider moves in a track, which is why the whole category of window stops, wedges and track locks exists: block the track and the sash cannot travel. The CPSC's window safety guidance turns on keeping an opening to four inches or less, and on a sash window a stop in the track does that.

A casement has no track. It is a hinged door in a frame, driven by a geared operator and held by a scissor arm, and it swings outward through a full 90 degrees. Three consequences follow, and they are why generic advice fails on these windows.

The opening is the whole frame. When a casement is open, there is no half-open position in the way there is with a sash. The gap is the entire window, which on a bedroom casement is routinely 20 by 40 inches - large enough for a child to pass through without touching the sides.

The crank is a toy. A geared operator is designed so an adult can move a heavy sash with one hand, which also means a two-year-old can move it with two. Locks and latches on the frame are irrelevant if the handle is reachable, because the operator drives the sash open regardless.

It opens outward. A child leaning on a closed casement is leaning on glass in a frame, which is fine. A child leaning on a casement opened four inches is leaning on a pane that swings away from them.

The four fixes, strongest last

One: remove the crank handle. On most casements made in the last thirty years the handle is either a push-on fit with a small set screw, or a folding handle held by a single machine screw. Take it off, store it somewhere adults can find it in a fire, and the window becomes inoperable to a child. Free, instant, reversible, and not sufficient on its own for an upper-floor bedroom because an adult will leave it on one evening.

Two: a keyed sash lock or a limiting device on the frame. Many casement manufacturers sell a vent limiter or an opening restrictor for their own windows, which holds the sash at a few inches and releases with a lever an adult can reach. Buy the one made for your window brand if it exists; a universal part on a geared casement tends to foul the arm.

Three: a hard limit on the operator arm. A clamp or stop on the scissor arm stops the window travelling past a set point. It is effective and it is also the fix most likely to be defeated by the next person who wants the window fully open on a hot day, so treat it as a semi-permanent choice rather than a setting.

Four: a window guard across the opening. This is the only fix that does not depend on anyone remembering anything. A guard with bars spaced under four inches, screwed to the frame, with an emergency escape release, is what the CPSC has pointed at since the ASTM F2090 standard was developed for exactly this job. On a casement, check two things before ordering: that the guard mounts to the frame or the reveal rather than inside a sash channel, and that fitting it does not block the crank so completely that an adult cannot open the window at all in an emergency.

The screen is not a barrier

This is the single most important sentence on any window page on this site, and it applies with particular force to casements because a casement screen is on the inside. An insect screen is held by a light frame and a few clips; it is designed to stop a fly, and a toddler's weight pushes straight through it. The CPSC has said this for decades and families keep learning it the hard way.

A screen on the inside of an open casement looks reassuringly like a barrier, which makes it more dangerous than an outside screen, not less. If the window is open and a child is in the room, the only thing between them and the drop is the guard - or you.

The guards that state the standard

Two of these three state compliance with ASTM F2090-21 with an emergency escape release, which is the specification to insist on for any bedroom above the ground floor. The third is the no-drill option, and the reason it is third is printed in its own listing.

Egress: the rule you must not break

A bedroom casement is very often the room's emergency exit, and in most US jurisdictions a bedroom is required to have an escape opening. That is why ASTM F2090 covers window fall prevention devices with emergency escape release mechanisms rather than just bars: the guard has to stop a child and release for an adult without a key or a tool.

So the hierarchy is: never fit a guard with no release to a bedroom window; never screw a window shut permanently; and never rely on a fix that an adult has to undo under smoke. Check your local code, and if the window is the only exit from a child's bedroom, choose the F2090 guard rather than the pressure-fit bars no matter how much easier the second one is to fit. The guards are ranked on best window guards and locks, the difference between a guard and a stop is on window guards vs window stops, and the whole-room pass for sash windows is on how to childproof windows.

One last job in the same room, because it is the hazard people forget while they are looking at the window: the blind. A looped cord beside a window is a strangulation risk independent of the fall risk, and it is dealt with on blind cord safety.