Window Won't Stay Up and Keeps Sliding Down: How to Fix It

Quick Answer

A window that slides down on its own has a broken or worn-out balance mechanism. In modern vinyl and aluminum windows, this is usually a coiled spring balance or a block-and-tackle balance. In older wood windows, it's a sash weight connected by a cord or chain. Replacing the balance is a DIY-friendly repair that costs $10 to $30 per window in parts.

Why Windows Slide Down

Every single-hung and double-hung window has a counterbalance system — a mechanism that offsets the weight of the glass sash so it stays where you put it. When you slide a window up and let go, the balance holds it in position. When that balance fails, gravity takes over and the sash slides down.

The type of balance depends on the age and style of your window.

Older wood windows (pre-1960s) typically use sash weights — heavy iron or lead weights hidden inside the wall cavity on either side of the window. They're connected to the sash by cotton cords that run over pulleys at the top of the frame. When the cord breaks (they all break eventually), the weight drops into the wall cavity and the sash loses its support.

Modern vinyl and aluminum windows use one of several spring-based balance systems:

Block-and-tackle balances — a spring-loaded pulley system inside a metal or plastic housing, attached to the sash with a clip or hook
Coil spring balances — a coiled spring in a tube, usually mounted in the window jamb
Spiral/tube balances — a spring-loaded rod inside a tube that twists and rotates to provide tension

All of these wear out over time. Springs lose tension, cords fray and snap, and the window starts slipping.

Fixing Modern Windows (Spring Balances)

Fixing Older Windows (Sash Weights)

Old sash-weight windows are mechanically simple but the repair requires access to the weight cavity inside the wall.

On the interior side of the window frame, there's usually a narrow panel called an access panel or pocket cover on each side, held by one or two screws or small nails. Remove this panel to reveal the sash weight inside the wall cavity.

You'll likely find the weight sitting at the bottom of the cavity with a broken cotton cord still attached. The repair is straightforward: tie new sash cord to the weight, run it over the pulley at the top of the frame, and attach it to the sash. Use proper sash cord (a braided cotton cord designed for this purpose) rather than nylon rope, which stretches and doesn't grip the pulley well.

Some people replace sash cords with sash chains, which last much longer and don't break the way cotton cord does. This is the upgrade I'd recommend if you're already in there doing the work.

Quick Temporary Fixes

If the window needs to stay open now and you'll deal with the proper repair later:

A window stick or prop. A length of wooden dowel or a paint stir stick cut to the right height and placed in the track holds the window open. Low-tech but effective.
Window wedges. Rubber or plastic friction wedges sold at hardware stores press into the track and hold the sash by friction.
A small screw. Drive a short screw partway into the window track at the height where you want the window to stay open. The sash rests on the screw head. Not elegant, but it works in a pinch.

These are stopgaps, not solutions. A window that won't stay up is also a window that won't lock properly, which is both a security concern and an issue during storms.

When the Problem Isn't the Balance

Occasionally, a window slides down not because the balance is broken but because the sash has swollen (from moisture absorption in wood windows) and the increased friction overwhelmed the balance. In humid climates, this can coincide with doors sticking in summer — same cause, different manifestation.

Dirty or painted window tracks can also create enough friction to prevent the balance from holding. Clean the tracks thoroughly and apply a dry silicone lubricant (not WD-40 or oil-based lubricants, which attract dirt).

If the window frame itself is out of square from house settling, the sash may bind in some positions and be loose in others. A level on the window frame will tell you if this is the case.

Cost and Whether It's Worth It

Replacement balances cost $10 to $30 each, and most windows have two. The repair takes 20 to 45 minutes per window once you've done your first one. Having a professional do it typically costs $75 to $150 per window.

Given that a new window costs $300 to $1,000 or more installed, repairing the balance is almost always worth it — unless the window has other problems like fogged glass (a broken seal analogy), rotted frames, or severe air leakage. A window with a working balance but otherwise good condition has plenty of life left.