What are Block and Tackle Window Balances and How Do They Work?

Block and tackle window balances are a type of counterbalance system used in single and double-hung windows to make opening and closing the sash easier. These balances are one of the most widely used systems in residential windows today. Understanding how they work can help you make informed decisions when buying new windows or replacing balances.

What is a Block and Tackle Window Balance?

A block and tackle window balance, also known as a channel balance, is a device located in the window jamb that includes a combination of two or more pulleys, a cord, and a spring contained within a “U” frame channel. The “U” frame is a long square container with one open side. Some block and tackle systems also have “wings” which are small plastic attachments at the end of the “U” frame.

Block and tackle balances are selected based on the length of the metal channel and a stamp that indicates the weight range the balance is designed to support. They can be used in modern wood, aluminum, vinyl, and composite frame windows, but the specific style depends on the type of sash they will be operating.

How Do Block and Tackle Balances Work?

Block and tackle balance systems use an extension spring force to counterbalance the weight of the window sash. The pulley and cord system control the tension in the spring as the sash moves up and down in the frame.

In a tilt-sash window, a clip is attached to the end of the cord that runs through the locking terminal. This clip connects to a pivot shoe, which allows the window to move up and down and tilt-in for easy cleaning. Non-tilt windows have a hook at the end of the cord that slips into a slot near the center of the window jamb, stretching the cord as the window moves.

Benefits and Drawbacks of Block and Tackle Balances

One of the main benefits of block and tackle balances is their ability to provide a smooth, effortless operation for the window sash. They are also relatively easy to repair or replace if parts fail. However, these balances have many moving parts that can wear out over time, and the cord and springs may need to be replaced periodically.

If you notice the sash becoming heavier to lift or close, it may be a sign that something is wrong with the balance. Continuing to use the window in this condition can make the problem worse. In most cases, removing the sash and identifying the issue should be relatively straightforward.

To replace a block and tackle balance, you’ll need to remove the sash and the balance itself. If you can identify and source the original parts, the replacement process should be simple. Follow the manufacturer’s instructions carefully to ensure proper installation and operation of the new balance.