A window that will not close properly may be misaligned, swollen from moisture, blocked by debris, affected by loose hardware, or sitting in a distorted frame. Before forcing it shut, note whether it rubs at the same point, whether the frame is square, and whether the problem began after moisture, painting, or structural movement.
Clean tracks and check for obstructions
Grit, paint, insects, or displaced weatherstripping can block the last few millimeters of travel. Remove debris without bending the frame or cutting useful seals.
Look for rubbing or sash sag
If it contacts the top, bottom, or one side, compare gaps and tighten ordinary accessible hardware. A heavy sash or worn hinge may need system-specific adjustment.
Swelling or paint can reduce clearance
Damp wood and recent paint layers can make a previously functional window bind. Correct moisture and let paint cure before sanding structural material.
Frame distortion or cracking deserves evaluation
If several windows change at once, the frame is visibly distorted, or new cracks appear, do not adjust each sash just to hide the symptom. Building movement may need evaluation.