My wall started leaking sand ....

[JP_]

All was quiet, and then suddenly, a hole appeared and sandy stuff started pouring out.

What should I do? Winter is coming .....

1930s solid walls with painted pebble dash...

 

[Doggit]

Waters got in to the cracks, and softened the mortar behind it. You'll need to dig the hole out to get rid of the soft mortar, fill it with some sand and cement, and then repaint the surface and seal the cracks.

 

[chappers]

the way that's bubbled up, looks more like efflorescence behind the paint, hack the paint off around the area and see

 

[^woody^]

Barbed wire and guard towers in the meantime.

 

[JP_]

what do you mean, just keep an eye on things?

 

[Nige F]

It might be a hole for a pipe that's been filled and a few pebbles poked in - it has that appearance- so maybe a weak mortar mix was used, and rain has got into it. Possibly