How do I fix a casement window that has dropped?

A dropped casement shows as a handle that no longer lines up, a diagonal gap, or a window that fouls the frame as it closes. What is causing it depends entirely on what the window is made of.

What you'll need

• A screwdriver
• Glazing packers
• A bead lifter
• Replacement stays or hinges
• PTFE lubricant

Step by step

1. Measure the drop.Close the window and look at the gap at the top and bottom of the opening edge. A wedge shape tells you how much it has dropped and in which direction.
2. On uPVC, look at the stays.There are no hinges — the sash hangs on two friction stays. Worn arms, elongated screw holes or a bent stay all let the sash sag at the outer corner.
3. Check the glass packing.The sealed unit is what makes a uPVC sash rigid. If the packers have slipped, the sash frame racks into a parallelogram and drops. This is the most common cause and the most overlooked.
4. Toe and heel the glass to correct it.Take the beads out, lift the sash square, and pack under the bottom corner on the hinge side and the top corner on the opening side. That is what the glass is doing structurally.
5. Do it with the window closed and square.Close and lock the sash, then adjust the packers so the glass holds it in that position. Packing an open, sagging sash locks the sag in.
6. Replace the stays if they are the fault.Both of them, measured along the track. Fresh stays often restore the alignment on their own.
7. On timber, check the hinge screws.The top hinge takes all the load. Loose or stripped screws let the sash drop, and a long screw into the frame's structure usually cures it.
8. On timber, check the corner joints.A mortice and tenon that has opened lets the sash rack. Cramp it square, glue the joint, and consider a repair plate or a dowel through the joint.
9. Check the frame is not the problem.A frame distorted by a settling lintel or by over-tight fixings will never let a square sash close properly. Check the frame for square before adjusting the sash.
10. Reset the keeps last.Once the sash sits square, the handle and cams will be close to the right position. Small movements at the keeps finish it off.

Tips

• Toe and heel packing is the technique that professional installers use and almost no homeowner knows about. It is what makes a uPVC sash rigid and it corrects most sagging.
• If the handle used to line up and now does not, the sash has moved. Do not adjust the keeps to chase it — find why it moved.
• On a timber casement, a repair plate across the corner joint on the inside face is unsightly but honest and lasts.

Common mistakes

• Adjusting the keeps to compensate for a dropped sash — It gets the window closing again but leaves the sash racked. The seal compresses unevenly, the stays carry a twisted load, and the sash carries on dropping until the keeps run out of adjustment.
• Packing a uPVC sash while it is open and sagging — The packers set the shape the sash will hold. Packed in the sagged position, the sash is locked out of square permanently and the whole exercise has to be redone.

If it doesn't work

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