Symptoms
- Small gap at the top or bottom when latched
- Window feels like it hits something before fully seating
- Drafts even when locked
- Lock won't fully engage
Likely causes
- CommonDebris or paint buildup in the trackDirt or old paint can stop the sash from traveling its full distance.
- PossibleBent or warped sashImpact damage or age can bow the frame slightly.
- PossibleMisaligned or worn balanceA balance under too much or too little tension can hold the sash slightly open.
- PossibleForeign object in the frameToys, insects, or hardware fragments can lodge in the channel.
- Less commonSettling of the house shifting the frameOlder homes can rack the window opening out of square.
What to do
- Clean the full length of both side tracks with a brush and vacuum.
- Close the window slowly while watching both sides for where it catches.
- Check the lock cam and strike plate line up; loosen and reposition the strike plate screws if they don't.
- Look at the sash edges for visible warping or a bent metal frame on vinyl or aluminum windows.
- Test the balance tension by lifting the sash partway; if it feels unusually stiff or loose, that side likely needs adjustment or replacement.
- For wood windows, sand down a swollen edge slightly if it's binding against the frame.
- Recheck the fit after each adjustment before assuming a part needs replacing.
Tools and parts
- Vacuum
- Screwdriver
- Sandpaper
- Flashlight
Window strike plateSearch: “window sash lock strike plate”
When to call a pro
Call a window professional if the frame itself looks out of square or the sash is visibly warped, since that may mean the window needs replacing.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.