What is a window balance?
A spring or block-and-tackle mechanism inside a double-hung window frame that counterweights the sash so it stays in place when raised without external support.
Double-hung windows rely on a balance mechanism to lift and hold the upper or lower sash at any height without strain or the need for propping. This mechanism works by applying an upward force that offsets the sash weight, allowing smooth operation and secure positioning.
There are two main types. Spring balances use a tightly coiled spring that stores and releases energy as the sash moves, maintaining constant tension throughout the window's range of motion. Block-and-tackle balances (also called pulley or rope systems) use weights, cords, and pulleys mounted inside the frame to counterweight the sash. Modern windows typically use spring balances, while older homes in Connecticut often have the traditional cord-and-weight system.
Over time, balances fail for predictable reasons. Spring balances lose tension as the spring fatigues or corrosion builds up inside the tube. Cord-and-weight systems fail when rope frays or snaps from friction and age, or when cast-iron sash weights crack. Worn balances cause sashes to drop unexpectedly, resist opening, or require hand support to stay raised. Left unrepaired, a failing balance can damage the frame, crack glazing, or create a safety hazard.
Replacing or repairing window balances is one of the most common reasons homeowners call window repair specialists. The cost and complexity depend on whether you have spring or weight-and-pulley balances and whether the frame itself is intact.