Renovating our 1920's bungalow. 9" Solid brick walls.
We had injected DPC. Re-rendered/plastered inside. Internal walls not too bad though some bricks were loose/wobbly and had to be reset.
External walls need repointing where damp was worst.
In places, the entire depth of the mortar (3.5") is basically soil. Elsewhere, it is a bit more sandy.
I'm systematically removing the soil, brick or 2 at a time, and forcing fresh mortar (5:1:1) into the joints, resetting bricks where need be.
My question is, is there some natural process that could cause this in a damp wall over several decades, up to a few feet above ground ?
There are, unsurprisingly, woodlice and other insects in the flaky joints. Could these insects (masonry bees?) replace sand with soil ?
Or, horror of horrors, would anyone in the past have used soil in place of sand to build ? If so, I would have thought the place would be a pile of bricks by now.
Any insight (or sympathy?) would be appreciated.
Bear in mind, it's 1920's built in Lincolnshire.