uPVC Window Dropped? Why It Catches the Frame and How It's Fixed

A uPVC window that has dropped is one where the opening sash has sagged on its hinges, so the bottom corner on the handle side sits lower than it should. You notice it as a window that catches on the frame, needs lifting to close, won't lock without a shove, or lets in a draught along one edge. The cause is nearly always the friction hinges, sometimes the glazing packers, and occasionally a bent or broken stay. In most cases the frame and glass are fine and the fix is a hardware repair, not a new window.

How to tell a window has dropped

Open the window and look at the gap between the sash and the frame when it is nearly closed. On a window that hangs properly, the gap is even all the way round. On a dropped window, the gap is wider at the top on the handle side and tight or closed at the bottom. You may see a scuff mark on the frame where the sash has been rubbing, or a worn patch on the bottom edge of the sash itself.

Another sign is the handle. If the window used to lock with a light turn and now needs pressure, or you have to lift the sash before the handle will go down, the locking points on the sash edge are no longer meeting the keeps on the frame where they should.

• Sash catches the frame on the handle side when closing
• Uneven gap between sash and frame, wider at the top
• Handle stiff to lock, or only locks if you lift the window
• Draught or whistling along one edge
• Window swings shut or won't stay open

Why uPVC windows drop

Most uPVC casement windows hang on friction hinges, the flat metal arms hidden in the top and bottom of the frame when the window is shut. They carry the full weight of the sash and glass every time it opens. Over years of use, the rivets and pivots wear, the arms bend slightly, or the screws loosen in the frame. A sealed unit is heavy, so even a small amount of wear lets the sash sag.

The second cause is the glazing packers, the small plastic blocks that sit under and around the sealed unit inside the sash. They hold the glass in position and keep the sash square. If a packer has slipped or was set badly when the glass was last changed, the sash can twist out of shape and drop at one corner even with good hinges.

Less often, a restrictor stay or a child safety catch has bent, which stops the window opening and closing on its normal path. Leaning on an open window, or having it caught by the wind, are common ways hinges and stays get damaged.

What you can safely check yourself

Start by opening the window fully and looking at the hinges at the top and bottom. Check the screws that fix the hinge to the frame and to the sash. If any are loose, tightening them with the right screwdriver can sometimes take out a small drop. Don't overtighten into uPVC, as the screw can strip its hole.

Look for obvious damage: a bent arm, a cracked rivet, or a hinge that grinds or clicks as the window moves. Clean any grit out of the hinge track with a dry brush, and apply a little light lubricant to the pivots, then open and close the window a few times. Never lubricate a friction hinge heavily, because it relies on some friction to hold the window open.

Do not try to force a dropped window shut or to bend a hinge back into shape. On upstairs windows, keep your weight inside the room and don't lean out to reach the hinges. If the sash feels loose or wobbles when open, stop using it until it's checked, because a failing hinge can let go.

Can a dropped window be adjusted?

Some friction hinges have a small amount of adjustment, and re-setting the glazing packers can square up a twisted sash. That is a job of removing the beads, lifting the sealed unit slightly and repositioning the packers so the sash corners are supported properly. It needs care, because a sealed unit that is knocked or levered badly can crack.

When the hinges themselves are worn, adjustment won't last. Replacing the friction hinges is the reliable fix: the old hinges are unscrewed, new hinges of the correct size and type are fitted, and the sash is rehung and checked so it closes evenly and locks with a light turn. The window frame, glass and handle stay as they are.

When to call a glazier

Call when tightening loose screws hasn't helped, when a hinge is visibly bent or cracked, when the sash moves when you push it up, or when the window won't lock at all. Leaving a dropped window can also wear out the locking mechanism, because every forced turn of the handle puts strain on its gearbox.

Mark replaces worn friction hinges and resets sashes on uPVC windows. Send a photo of the window open, showing the hinge, and he can usually tell what's needed. Our hinges and handles page explains the hinge repair, and for other window faults see uPVC window repairs.

Call Mark on 07535 916982 or request a callback.