Window Sash

The window sash is the operable frame that contains the glass and moves to open and close the window. In a standard double-hung window, there are two sashes: the upper sash (which slides down from the top) and the lower sash (which slides up from the bottom). The sash is distinct from the window frame (also called the jamb box), which is fixed to the wall.

Sash vs. Frame

Understanding the difference between sash and frame is important for repair estimates:

• Window frame — fixed structural element: head (top), sill (bottom), and two jambs (sides). Does not move.
• Window sash — moves. Contains the glass. Can be replaced without replacing the frame.

Common Sash Problems

• Stuck sash — painted shut, warped wood, or failed balance springs prevent operation
• Broken sash cord or balance — sash won’t stay up in the open position
• Failed IGU seal — the glass within the sash has fogged; the sash itself may be fine
• Rotted wood sash — common in older homes; requires sash replacement or epoxy repair

Sash Replacement vs. Full Window Replacement

If the frame is sound, replacing only the sash kit (a pre-assembled sash with new IGU and hardware) is significantly cheaper than full-frame window replacement. Many window manufacturers sell sash kits for their specific window lines. A professional installer can swap out both sashes in under an hour.