How do I replace a door latch?

A latch is a consumable. The spring inside fatigues after a decade of use, and when it goes the handle stops returning and the door stops holding — which people usually blame on the handle.

What you'll need

• A replacement latch of the same backset
• A screwdriver
• A tape measure
• A sharp chisel, if the mortice needs easing

Step by step

1. Confirm the latch is the fault.Take the handles off and work the latch with a screwdriver in the spindle hole. If it is sluggish or does not spring back with the handles removed, it is the latch and not the ironmongery.
2. Remove the handles and spindle.Undo the rose or backplate screws, pull both handles off and slide the square spindle out.
3. Remove the forend screws.The two screws through the plate on the door edge. Then pull the latch out by the faceplate — a screwdriver behind the plate levers it if it is tight.
4. Measure the backset.From the door edge to the centre of the spindle hole. UK tubular latches are almost always 57mm or 76mm; mortice sash locks come in 64mm and 76mm cases.
5. Measure the case as well.Length and depth of the body. A longer case needs a deeper mortice; a taller one needs the mortice extending, which is far more work than swapping like for like.
6. Check the follower size.The square hole the spindle passes through is 8mm on almost all UK domestic ironmongery, but check before buying so the existing handles still fit.
7. Match the forend shape.Square or radiused. A radiused plate in a square recess leaves two visible gaps; a square plate in a radiused recess will not sit down at all.
8. Fit the new latch.Slide it in, check the latch bolt's sloped face points towards the closing direction, and screw the forend down. Test with the spindle before refitting the handles.
9. Check the strike alignment.A new latch may project a fraction differently. Close the door slowly and watch the bolt meet the strike plate; ease the plate or the mortice behind it if it catches.
10. Deal with catches separately.On a door with no latch — a wardrobe, a cupboard, a knob-only door — the holding is done by a roller, ball or magnetic catch, all of which adjust rather than being replaced.

Tips

• Photograph the latch before you buy. The forend shape and the case markings are far easier to match from a picture than from memory.
• A roller catch that will not hold usually just needs its adjusting screw turning out a quarter turn, or the strike plate packing forward with card.
• Buy a latch with an adjustable backset if you are not certain — they cover 57mm and 76mm in one body.

Common mistakes

• Buying a latch by length rather than backset — The backset determines where the handle sits relative to the door edge. Get it wrong and the spindle hole in the door no longer lines up with the latch, which means either a new hole through the door or starting again.
• Fitting the latch bolt the wrong way round — The sloped face has to point the way the door closes so the bolt rides over the strike. Fitted backwards the door simply will not shut, and the latch has to come out again.

If it doesn't work

Questions people ask