Sash Weights, Cords & Pulleys

Traditional box sash windows use counterweights to balance the weight of moving sashes. A cord runs over a pulley and connects the sash to a weight concealed inside the case.

Understanding the details

Broken cords, seized pulleys, missing weights or alterations to glazing can upset the balance. Safe access to weight pockets requires an understanding of the construction.

What to look for

A sash that drops or will not stay open should be assessed before continued use; heavy sashes can cause injury.

How the balance works

A cord passes over a pulley at the head of the case and connects each moving sash to a concealed weight. Correct balancing reduces the effort needed to raise and lower the sash.

Common failures

Frayed cords, seized pulley wheels, obstructed weight pockets and changed glazing weight can cause difficult operation. A sash that suddenly falls should be treated as unsafe until inspected.

What a survey records

Check the movement of both sashes, visible cord condition, pulley action and signs of earlier alterations. Opening weight pockets and handling heavy sashes should be undertaken with appropriate care.

Related archive guides

Continue with our window anatomy guide, technical glossary and research resources. This educational material is general guidance, not a substitute for a property-specific conservation assessment.