When a door stops latching: checks to make first

The single most useful test

Open the door. With it standing open, turn the key or the thumbturn and watch the bolt.

• The bolt throws smoothly and fully. The lock is fine. The problem is alignment, and everything below applies.
• The bolt sticks, grinds or will not extend fully. Now you have a hardware problem, and it is worth reading the repair and replacement page.

That one test resolves the majority of calls. People replace working locks because nobody suggested opening the door first.

Check 2: look at the gap along the top

Close the door and look at the line where it meets the frame across the top edge. It should be roughly even. If it tapers — wider at the handle side than the hinge side, or the reverse — the door has dropped or racked in its opening. A dropped door puts the latch below the strike pocket, which is precisely why it needs lifting before it will catch.

Check 3: find the witness marks

Look at the strike plate, the metal plate on the frame. There will be shiny scrape marks where the latch has been hitting it. Where those marks sit tells you which way the door has moved:

• Marks below the hole — the door has dropped.
• Marks above the hole — the door has risen, or the frame has settled.
• Marks around the edge of the hole — the door is not closing far enough, often because of weatherstripping or a build-up of paint.

This is the same diagnosis a locksmith makes in the first thirty seconds, and you can make it yourself for nothing.

Check 4: the hinge screws

Open the door and look at the top hinge, the one carrying the most weight. Try tightening its screws with a screwdriver. If any of them spin without biting, the screw has lost its grip in old timber, which is one of the most common reasons a door drops.

The fix is often a longer screw — three inches, driven through the jamb into the framing behind. That single change lifts a good number of doors back into alignment. Where the hole is chewed out entirely it needs plugging first.

Check 5: the season

If the door was fine in February and started sticking in July, you have a humidity problem rather than a hardware problem. Timber doors in the District can move noticeably between a dry winter and a humid August, and older solid-wood doors move more than modern ones.

Resist the urge to plane the edge in August. Come November it will have shrunk back and you will have a permanently loose door with a gap. Adjusting the strike gives you room without removing material.

Check 6: the key itself

If the symptom is at the key rather than the door — going in reluctantly, needing to be jiggled, or turning only in one position — look at the key before the lock.

• Is it a copy? A copy of a copy loses depth at each generation, and eventually it stops lifting the pins properly.
• Does another key for the same lock behave better? That answers it outright.
• Are the edges of the cuts rounded compared with a newer key?

A fresh key cut from the original, or from the lock's code, ends a surprising number of “the lock is failing” complaints. Where the cylinder genuinely is stiff, it may only need cleaning and repinning, which happens as part of rekeying.

What is worth calling about

If checks 1 to 6 point at alignment and you are comfortable with a screwdriver, much of it is a straightforward afternoon. Call when the bolt itself is failing, when the frame is damaged, when a key has broken off, or when you have adjusted the strike twice and it has moved again — that last one usually means something structural rather than something fixable at the door.