Window Sash Won't Stay Up: Balances, Springs, and When It Is a Safety Problem

A sash that will not stay up is not being stubborn. It is telling you its counterweight has quit. Every double-hung and single-hung window has a hidden system doing the heavy lifting for you — a balance, a spring, or, in an older Los Angeles house, a cast-iron weight on a cord inside the wall. When that system works, a heavy sash full of glass feels almost weightless and stays exactly where you leave it. When it fails, the sash slides shut on its own, creeps down a few inches at a time, or drops like a guillotine the second you let go. The good news is that in most cases the window itself is fine. The part that failed is small, specific, and replaceable.

First, identify which system your window uses

You cannot order the right part until you know what is inside the frame, and there are four common systems. Open the window partway and look at the side channels and the top corners of the sash before you touch anything else.

• Channel balances. The most common system in modern windows. A metal channel sits in each side jamb, with a spring and a cord or pulley arrangement inside it. It connects to the sash through a small clip or shoe at the bottom corner. When the cord snaps or the spring tires, that side stops carrying its share.
• Spiral balances. A tube in the side jamb with a spiral rod inside that twists as the sash moves. Common on older aluminum and some vinyl windows. The rod end and its color-coded bushing tell you the strength. A spiral balance can sometimes be re-tensioned, but a fatigued or corroded one needs replacement.
• Constant-force and block-and-tackle springs. Coiled spring systems used in many newer vinyl windows. They are quiet and compact, and when the coil cracks or the housing breaks, the whole cartridge on that side is replaced.
• Weight and pulley. The original system in pre-war and historic homes: a rope or chain over a pulley, tied to a cast-iron weight hidden in a pocket inside the wall. When the cord rots and snaps, the weight drops to the bottom of the pocket and the sash has no help at all.

On our window and door service and repair calls, identifying the system and reading the stamp on the old balance — most channel balances are stamped with a length and strength code — is the step that separates a one-visit repair from a return trip with the wrong parts.

What the symptoms are telling you

A sash that drops straight down the moment you release it has usually lost both sides, or lost its connection to the balances entirely — a snapped cord, a broken shoe, or a balance that has pulled free of its clip. A sash that stays up but tilts, binds on one side, or creeps down slowly has usually lost one side only: the good balance is carrying double duty and will not last long doing it. A sash that is hard to raise but stays up once it is there points the other way — a balance that is too strong, a spiral balance wound too tight, or simple friction from swollen paint, dirt in the tracks, or a sash that is racked in the frame.

Do not ignore the slow creep. It feels minor, but it means one side is already gone, and every cycle puts the full weight of the glass on a part rated for half of it. The second failure, when it comes, is the sudden one.

When a nuisance becomes a safety problem

This is the part people underestimate. A double-hung sash is a heavy sheet of glass in a frame, held up only by those two small mechanisms. When it falls, it falls fast, and it lands on whatever is in the way — fingers on the sill, a child's hands, a pet. A sash that drops without warning is not an inconvenience to live with until spring. It is a hazard in a room people use every day, and it should be treated that way: keep it closed and locked, or secured, until it is repaired.

It is also a security and weather problem. A sash that will not stay up often will not sit square in the frame either, which means the lock may not fully engage and the weatherstripping may not compress. You can end up with a window that looks closed, is not locked, and leaks air and water at the meeting rail. If the falling sash has cracked the glass, twisted the frame, or pulled the side jamb loose, the repair has grown beyond balances — stop there and have the whole unit looked at.

What a proper repair actually involves

Balances are replaced in matched pairs, never one at a time, because a new balance next to a tired one just repeats the one-sided problem. The replacement has to match the original in length, strength, and end fittings — too weak and the sash still falls, too strong and it will jump up on its own and fight you on the way down, which is its own kind of failure. The shoes, clips, and pivot bars at the sash corners get inspected at the same time, because a worn pivot shoe is often what let the balance disconnect in the first place.

For a weight-and-pulley window, the repair means opening the access panel in the weight pocket, fishing out the dropped weight, and re-cording — ideally with chain or a quality sash cord rated for the job — on both sides. On a historic home that work is worth doing properly, because the original system, once restored, will outlast most modern replacements.

One warning about doing this yourself: a loaded channel balance is a spring under tension, and a sash with a disconnected balance can drop while you are working on it. If you prop a sash temporarily, prop it to work safely for a short time — never as the fix. A book or a stick in the frame is not a repair, and it will eventually be knocked loose at the worst moment.

Repair the balances, or replace the window?

If the frame is sound, the glass is clear, and the sash moves smoothly once it is supported, new balances are the whole job — there is no reason to replace a good window over a wear part. Replacement starts to make sense when the balances are only one item on a longer list: rotted or cracked frames, failed insulated glass, sashes that are warped or racked, or hardware and parts that are obsolete and no longer made for that window. The honest test is simple. Fix the counterweight system and ask what is left. If the answer is a solid window, you are done. If the answer is three more problems, price the window.

If your sash is dropping, creeping, or tilting, do not keep propping it and hoping. Send us a photo of the window, the side channel if you can see the balance, and any stamp numbers on the metal channel. We will identify the system, tell you plainly whether it is a balance repair or something bigger, and give you an exact quote.