How to Fix a Window That Falls Closed (or Won't Stay Up): Replacing Sash Balances (2026)
A double-hung window that falls closed has a broken or failed sash balance — the spring or cord mechanism that counterweights the sash. This guide covers identifying your balance type, replacing spiral balances, and adjusting tension.
Window falls closed: (1) Modern vinyl and aluminum windows use spiral balances (a metal spiral rod inside a channel on each side of the window). A broken spiral or a balance that has lost tension causes the window to fall. (2) Try adjusting tension first: with the window closed, use a flathead screwdriver to wind the spiral clockwise 2–3 full turns in each spiral balance (the spiral is visible at the top of each side channel). Test the window. (3) If adjusting does not help: replace the spiral balances. They are available at window supply stores by balance length and balance weight stamp (a letter+number code stamped on the balance). (4) Older homes with wood windows may have sash cords and cast-iron sash weights — replacing these requires removing the parting bead and accessing the weight pocket in the wall.
Frequently Asked Questions
How do I know what type of balance my window has?
Window balance identification: (1) Spiral balances (tube balances) — a cylindrical aluminum tube on each side of the sash, 10–30 inches long. A metal spiral rod inside the tube stores spring energy. The most common type on vinyl windows manufactured after 1980. (2) Block and tackle balances — a flat channel on each side of the window with a cord, pulley, and spring block inside. Used on many vinyl windows made from 1990 to present. The external channel looks like a flat plastic strip. (3) Sash cords and weights — a braided rope running over a pulley at the top of the window jamb, attached to a cast-iron weight inside the wall cavity. Found in wood windows pre-1960. The rope frays and breaks after 50+ years. (4) Constant force (coil) balances — a flat steel ribbon coiled inside a housing at the top of the window. Used by some manufacturers for heavy sashes. To identify: look at the side of the window sash where it contacts the window frame — the type and profile of the balance mechanism there tells you which system you have.
How do I replace a spiral balance on a vinyl window?
Spiral balance replacement: (1) With the window open about 4–6 inches, find the tilt latches (buttons or levers at the top corners of the sash). Pull both toward the center simultaneously and tilt the sash inward toward you. This tilts the sash out of the window frame without removing it completely. (2) The spiral balance is the tube attached to the shoe (a plastic slider that runs in the channel). The top of the balance rod has a pin that fits into a hole at the top of the channel. The bottom of the spiral attaches to the shoe via a hook. (3) Twist the spiral clockwise to relieve tension, unhook the bottom from the shoe, then pull the top pin out of the channel. Remove the balance. (4) Measure the balance length and find the weight stamp on the balance body (a letter + number, e.g., 'B' + '14' or '2510'). Order an exact replacement — the weight code determines the spring tension needed for your sash weight. (5) Insert the new balance top pin, hook the bottom into the shoe, and wind the spiral counterclockwise 3–4 turns to pre-tension before re-tilting the sash in.
How do I replace a sash cord on an old wood window?
Sash cord replacement (old wood windows): (1) The sash cord runs from the sash side groove, over a pulley at the top of the window frame, down the wall to a cast-iron sash weight hidden in a pocket in the wall. (2) Remove the lower sash: pry off the stop bead (narrow wood strip on the interior face of the window jamb — it is nailed and can be pried without breaking with care). Slide the sash sideways and tip it out. The knotted cord end pops out of the groove in the sash side. (3) Access the sash weight pocket: there is a small removable panel at the lower end of the window jamb channel. Remove the panel and retrieve the sash weight from the wall pocket. (4) Remove the old cord. Thread a new sash cord (waxed cotton or nylon, same gauge) over the pulley — use a metal chain or thin wire as a threading leader if needed. (5) Tie the cord to the sash weight (slip knot with a stopper knot). Pull the cord until the weight is 3–4 inches from the pulley. Knot the cord end into the sash groove. Replace the pocket panel, re-hang the sash, and reinstall the stop bead.
My window will stay open at one height but falls from any higher position. Why?
Partial tension loss: this means the balance still has some spring energy but not enough to support the full sash weight at the top of travel. Causes: (1) Spiral balance has partially unwound — the coil lost some tension but is not fully broken. Solution: add more clockwise tension turns to the spiral (try 2–3 more turns than what is currently set). (2) One balance is working, the other is failed or low-tension — the window stays open when slightly open because the working balance can handle the load at that geometry, but falls from higher angles where the mechanical advantage changes. Check both balances. (3) Block-and-tackle balance with a stretched spring block — the spring inside the block has fatigue-stretched and provides less force. Replace the balance block. (4) Sash weight imbalance — on cord-and-weight windows, if one weight was lost or incorrectly replaced with a lighter weight, the cord side with less weight allows that side to fall. Both weights must match the sash load.
Can I use a prop stick or window support bar instead of fixing the balance?
Prop sticks and window support bars: (1) A window support bar (accordion-style metal prop) is a legitimate temporary fix and works well for windows where the balance repair is complex or the window is scheduled for replacement. They cost $5–$15 at hardware stores. (2) For safety: if the window prop fails or is kicked out, the sash can fall rapidly — avoid this in locations where children could put their arms or heads in the opening. (3) Proper balance repair is the correct long-term solution. Spiral balance replacement costs $10–$25 per window and takes 15–30 minutes. (4) Do not use a wood stick propped against the frame — sticks slip and the window can slam shut on fingers or damage the frame. Use a purpose-made adjustable prop that locks in position. (5) If the window is being replaced within 1–2 years: a support bar is a reasonable stopgap. If the window is structurally sound and you intend to keep it: replace the balance.
Window falls closed: (1) Modern vinyl and aluminum windows use spiral balances (a metal spiral rod inside a channel on each side of the window). A broken spiral or a balance that has lost tension causes the window to fall.
Try adding clockwise tension turns first — many failed spiral balances just need re-winding.
What you need
- Flathead screwdriver (for spiral balance tension adjustment)
- Replacement spiral balances (match length and weight code)
- Utility knife or pry bar (for removing window stop bead, wood windows only)
- New sash cord (for old wood windows with cord-and-weight system)
Step 1: Identify the balance type
Look at the side channel: cylindrical tube = spiral balance. Flat strip = block-and-tackle. Rope visible = sash cord and weight.
Step 2: Adjust spiral balance tension
With the window closed, insert a flathead screwdriver into the spiral rod slot. Turn clockwise 2–3 full turns on each side. Test the window — it should now stay up under its own weight.
Step 3: Replace broken spiral balances
Tilt the sash inward at the tilt latches. Disconnect the old balance (twist to unload, unhook from shoe, pull top pin). Note the weight code. Install replacement with 3–4 turns of pre-tension.
Step 4: Replace sash cord (old wood windows)
Remove the stop bead and lower sash. Access the weight pocket. Thread new cord over the pulley, attach to the sash weight, knot into the sash groove.
Related guides
- How to Fix a Window That Won’t Stay Open — spiral balance tension and casement operator repair
- How to Seal Drafty Windows — air sealing around window frames
- How to Replace a Broken Window Pane — glass replacement for single-pane windows
- Identify the balance type
Most double-hung windows use one of three balance types. Spiral balance: a metal rod with a coil spring inside a tube, visible on the side jamb when the sash is tilted in — the rod has a plastic tip that hooks into the sash pivot. Channel balance (block and tackle): a flat ribbon or cord mechanism inside a metal channel on the jamb — the sash clips onto a shoe that slides in the channel. Weight and cord (older wood windows): a cast iron weight hanging inside the wall cavity, connected to the sash by a cord over a pulley. Identifying the type determines the replacement procedure.
- Replace a spiral balance
Tilt the sash in by pressing the tilt latches inward and pulling the top of the sash toward you. The spiral balance rod tip unhooks from the pivot shoe on the sash. Note the balance stamp code (a letter-number combination like 'S320' printed on the tube) — this specifies the length and spring tension needed. Order a replacement with the same code (or measure the tube length and sash weight to match). Install by pressing the tip into the pivot shoe and rotating the rod clockwise to load the spring tension per the replacement instructions.
- Replace a channel balance shoe
For channel balance (block-and-tackle) windows: the sash is connected to a plastic shoe that rides in a metal channel. The shoe can crack or the clip that connects the sash to the shoe can break. Tilt the sash in, unclip the sash from the shoe, and slide the shoe out of the channel. Match the replacement shoe to the channel width (typically 3/4 inch or 1 inch). Snap the new shoe into the channel, connect the sash clip, and tilt the sash back into position.
- Repair a weight and cord balance
For older wood windows with cast iron weights: if the cord has broken, the weight hangs free in the wall cavity and the sash falls. Access the weight pocket by removing the access panel on the lower jamb (a small rectangular piece of wood held by two screws). Reach in and retrieve the weight. Thread new sash cord over the pulley at the top of the jamb and tie it to the weight. The other end attaches to the sash through a groove in the sash side rail — knot the cord in the hole and pull it taut so the weight hangs at mid-pocket when the sash is fully open.
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