How to Fix a Broken Window Sash: Rope, Spring, and Balance Repair

A window sash that falls down when you open it, slams shut on its own, or won’t stay up at any position has a failed balance system.

A window sash that falls down when you open it, slams shut on its own, or won’t stay up at any position has a failed balance system. The repair is specific to how the window was built — and the three main balance types span roughly 100 years of residential window construction.

Identify your balance type first. Getting this right before you buy anything saves time and money.

Diagnosing Window Balance Type

Sash rope and counterweight (pre-1960 wood windows): Open the window partway and look at the side channels (the grooves the sash slides in). You should see a rope or chain attached to the side of the sash, running up and over a small pulley at the top of the channel. If the rope is frayed, missing, or there is just a dangling end with no tension, the rope has broken. These windows have hollow wall pockets on each side that contain heavy cast-iron weights.

Spiral balance (1970s through mid-1990s): Look at the sides of the sash channel. You will see a metal tube — usually white or bronze, about 1-2 inches in diameter — running vertically in a channel on each side of the frame. The bottom of each tube attaches to the sash via a plastic “shoe.” These use a coiled spring inside the tube that stretches and contracts to counterbalance the sash weight. If the spring is broken or the shoe has cracked, the sash falls.

Block-and-tackle balance (1990s to present): Common in newer vinyl and clad-wood windows. Look for a white plastic or metal cartridge visible inside the sash channel, usually with a cord running to the sash. The cartridge contains a series of pulleys (the “block”) and a coiled spring (the “tackle”). These are often manufacturer-specific and may require ordering a replacement from the window manufacturer.

If you are unsure which type you have, take a photo of the full window frame and a close-up of the sash channel and bring it to a window supply shop — they can identify it immediately.

Fix 1: Sash Rope Replacement

What you need:

• Replacement sash rope — #8 or #10 solid-braid cotton or poly rope (not twisted — it will stretch unevenly)
• Utility knife or scoring tool
• Pry bar and stiff putty knife
• Hammer
• 10-penny (10d) finish nails or screws

Steps:

1. Remove the interior stop bead. Score the paint line between the stop bead (the thin strip of wood that holds the lower sash in its channel) and the window casing. Use a utility knife and go back and forth several times. Then carefully pry the stop bead away from the casing — it is usually only nailed, not glued, and can be reused.

2. Swing out the lower sash. With the stop bead removed, tilt the bottom of the lower sash toward you and swing it out of the frame. The old rope (if still attached) will pull taut on the sides.

3. Disconnect the old rope. The rope is typically nailed or knotted into a channel or hole on the side of the sash. Remove the nail or cut the rope and remove the sash completely.

4. Access the weight pocket. On the lower portion of each side channel, there is a small access door (the pocket cover) — a section of the interior trim that is screwed or pried off to reveal the weight cavity. Remove it and reach in to pull out the cast-iron counterweight. The broken rope end will be tied to it.

5. Run the new rope. Tie a small nail or “mouse” (a washer or bolt) to a length of string, then feed the string over the pulley at the top of the channel and let it fall into the weight pocket. Tie the new sash rope to the string and pull it over the pulley. This is the trickiest part — old pulleys can be stiff and the pocket cavity has little room to work.

6. Tie to the counterweight. Pull the rope through the pocket until you have enough to tie securely to the counterweight’s eye hook. Use a bowline knot. Lower the weight back into the pocket.

7. Set the rope length. Hold the sash in the fully open (raised) position. The counterweight should hang about 2-3 inches from the bottom of the pocket — not touching the bottom. Cut the rope at the correct length and nail or tie it into the sash’s rope channel. A 10d finish nail driven through the rope and into the sash side is the traditional method.

8. Reinstall the sash and stop bead. Test the sash travel through its full range before nailing the stop bead back. Adjust the stop bead gap so the sash moves smoothly without wobbling.

9. Repeat on the other side. Even if only one rope broke, replace both — they age together, and the second will break within a season.

Fix 2: Spiral Balance Replacement

What you need:

• Replacement spiral balance — must match the length and tension code of your original
• Flathead screwdriver
• Drill (if screws are involved)

Identifying the replacement balance: The tension code is stamped or printed on the spiral balance tube — look for a number like “20,” “30,” or “40.” This indicates the spring tension, which corresponds to the sash weight. You also need the exact tube length. Measure the old balance or look up the window model. Swisco.com is a reliable source for spiral balances by size and tension code, and they have identification guides.

Steps:

1. Tilt the sash inward (if it is a tilt-in sash — pull the tilt latches on the top corners of the sash). If the sash does not tilt, remove the interior stop bead and swing the sash out as in the rope replacement procedure.

2. Unhook the balance top pin. The spiral balance has a metal pin or hook at the top that fits into a hole or bracket in the window frame. Use a flathead screwdriver to rotate the spring — the pin will drop out of its hole. Note the direction of rotation (clockwise on most brands to release tension).

3. Unclip the bottom shoe. At the bottom of each spiral balance is a plastic shoe that clips onto a pin or tab on the side of the sash. Squeeze or pry the shoe off.

4. Install the new balance. Hook the top pin of the new balance into the frame bracket. Pre-tension the spring by rotating the tube (usually clockwise) with a flathead screwdriver until the spring is taut — the number of rotations is specific to the balance tension and is printed on the package. Clip the shoe onto the sash pin.

5. Test and reinstall. With both balances installed, tilt or replace the sash and test it through its full travel range. The sash should hold position at any height without falling.

Fix 3: Block-and-Tackle Balance

Block-and-tackle balances are more varied in design than spiral balances and are often proprietary to the window manufacturer. Before attempting a repair, identify your window brand and model (often on a label on the frame near the hinges or on the sash itself) and contact the manufacturer or a window parts supplier.

The general replacement procedure:

1. Tilt the sash in or remove it per the manufacturer’s method.
2. The balance cartridge is typically screwed into the frame channel. Remove the screws.
3. Disconnect the balance cord from the sash attachment point.
4. Install the new cartridge, attach the cord, and reinstall the sash.

Because block-and-tackle balances vary so widely, the manufacturer’s documentation or a window parts supplier’s video walkthrough is the most reliable guide for your specific model.

Fixing a Painted-Shut Window

A window sash that has been painted shut is a different problem from a failed balance — the sash physically cannot move because layers of paint have glued it to the stop bead and parting bead.

What you need:

• Utility knife or paint zipper
• Wide putty knife (3-4”)
• Hammer
• Sash paint guard (to prevent repainting the sash shut)

Steps:

1. Score the paint line. Run a utility knife along the line where the sash meets the interior stop bead and along the exterior meeting rail. Make multiple passes, pressing firmly. Go all the way around the perimeter of the sash — top, sides, and bottom.

2. Break the bond. Insert a wide, stiff putty knife into the gap between the sash and the stop bead and tap it gently with a hammer. Work in small increments around the frame. The goal is to crack the paint film, not to pry the window open by force. Prying from one point cracks glass.

3. Score the exterior. Go outside and score the paint line between the sash and the exterior casing or sill with a utility knife. The exterior paint bond is often thicker than the interior.

4. Lift the sash. Once the paint is broken all the way around, the sash should lift with moderate effort. If it still doesn’t move, score again and work the putty knife around again.

5. Prevent recurrence. Before repainting, apply painter’s tape to the sash edges or use a sash guard tool. Paint the stop bead and the sash edges separately and allow both to dry fully before closing the window. Never close a freshly painted window.

Related Reading

• How to Fix a Sticking Window
• How to Replace a Window
• How to Fix a Foggy Window