On Mon, 25 May 2020 17:42:22 +0100, in uk.d-i-y Caecilius wrote:

One of my internal doors slowly swings fully open unless it's latched
closed. None of the other identical doors do this so I think it's
something to do with how it's hung, but I can't find any obvious
problems. It's a solid hardwood door (so pretty heavy) hung on two
brass hinges.

A spirit level shows that the door frame on the hinge side is
vertical, and the hinge side of the door is vertical as well. A plumb
bob made from a nut&bolt on a piece of string shows that the two
hinges are in line vertically.

Any ideas on what could be causing this?

It does not take much mis-alignment of the hinges from true vertical to cause this, and it's difficult to prove mis-alignment with plum-bobs due to the door and frame getting in the way of the bob.

However, for this to happen the hinge axis must be leaning from the vertical towards the opened edge. You may also notice that the bottom far corner of the door gets closer to the floor as it swings open, a sure sign the hinges aren't quite vertical (assuming the floor is horizontal!).

I have just fixed the same problem of a self-opening door in my Victorian house where the frame must have shifted a bit over the years causing misalignment.

Let the door swing to its open position. To fix it the top hinge axis needs to be moved away from the door, to slightly lift the far edge. Alternatively the bottom hinge can be moved the other way (or both moved a bit).

This will require you to drill out and plug the existing screw holes with 6mm dowel plugs. Also, moving the hinge positions will likely require the door-stopping to be taken off and re-nailed afterwards.

The way I did mine was to confirm the far edge of the door drops as it swings open, then anticipating that the hinges were to loosened/removed, I clamped a couple of my largest tri-squares to the door edge to stop it leaning over.

Next I knocked 4 wedges tightly under the door, 2 each side, to take its weight (this was a heavy solid wooden door), then loosened the bottom hinge screws and completely removed those from the top hinge. Also prised the hinge blade free from its rebate - taking care the door didn't start to lean over!

I then carefully knocked the wedges further in, lifting the edge of the door till the edges were vertical and the top horizontal. Next I drilled out the screw-holes and glued in 6mm dowel plugs.

I had to widen the hinge rebate by about 3mm because the hinge blade will be moved a bit further over.

Then its a matter of accurately centring new holes for the screws. I did this by finding one of those wood drill bits with a sharp pointy end that is close to the hole diameter in the hinge blade. Carefully tap this drill through the hinge hole to make a small starter hole. Then flip back the hinge and finish drilling the screw holes, ideally with a proper screw-sink bit.

When satisfied with the door swing, re-fit the door-stopping (and touch-up paintwork!)

It might also be necessary to pack out the hinges if the door isn't square in the frame.

Phil