Sash Window Add-On Weights

Why Sash Weights Matter in Double-Hung Windows

Double-hung sash windows rely on only a few key components to function properly — and one of the most important is the counterweight.

⚖️ The Role of Sash Weights

Each moveable sash (pane of glass) in a double-hung window is connected to a hidden weight inside the window frame. A sash cord runs over a pulley at the top of the frame, connecting the sash to this weight. The counterweight balances the sash, allowing it to move smoothly and stay in place when opened.

🔧 Why Rebalancing Is Essential

Anyone in the window restoration trade knows that rebalancing is an essential part of servicing sash windows. Most often, problems with sticky, stiff, or dropping windows are due to incorrect weight distribution.

Over time, windows may be reglazed with heavier glass — for example, replacing old 2mm glass with 3mm glass — adding extra weight to the sash. If the counterweights haven’t been adjusted, the window can become unbalanced and potentially dangerous.

Incorrectly balanced windows:

• Are difficult or awkward to open
• Can slam shut unexpectedly
• May cause damage to the frame or sash if dropped

🧱 Add-On Weights – A Simple Solution

Most rebalancing jobs require adding weight, not removing it. That's where add-on weights come in — small supplementary weights that fine-tune the balance of your sash.

Unlike most add-on weights on the market (which are square), our weights are round and domed. Why? Because original sash weights are round, and inserting square weights can cause friction issues inside the sash box.

Our smart design allows the add-on weights to fit seamlessly onto existing round weights, ensuring smooth movement and easy installation. Available in:

• ½ pound (approx. 225g)
• 1 pound (approx. 450g)

🛠️ How to Rebalance Your Double-Hung Sash Window

1. Remove the sash window
2. Access the weights: Open the pocket cover inside the sash box. Untie the sash cord, pull it through the pulley, and remove the existing weights.
3. Top sash: Weigh the sash (bathroom scales work). Add 1 pound (approx. 0.46kg) to the total, then divide by 2. That’s the weight needed on each side.
4. Bottom sash: Weigh the sash and divide the total by 2. That’s the weight required on each side.
5. Thread the new sash cord: Use a small string with a weight to guide the new cord through the pulley. Tie the sash weight securely to the end of the cord with a knot to prevent slippage.
6. Reinstall the sash: Carefully replace the sash in the frame. You may need an extra set of hands to hold the sash while you pin the cords into place using galvanized nails.

Whether you're restoring a heritage window or upgrading modern timber joinery, our round add-on sash weights make rebalancing faster, safer, and smoother.