Rendering and damp proof course

RedPen

We've got mould growing on the inside of many of our internal (north facing) walls of our house, upstairs and downstairs, behind furniture.

The house was build in 1979

Chalet bungalow (upstairs with slanted ceilings and cupboards in the eaves)

The slopping roof is tiled and the dorma bathroom was redone about 12 years ago with a slopping roof.

2 air bricks on SE wall - OK

No cavity wall insulation (I'm not sure there is a cavity)

Property is rendered

No leaking guttering

Double glazing installed 12 years ago, no trickle vents

We've lived here 5 years

No survey was done

The walls are made of these large blocks that look a bit like breeze block but are really heavy and a darker grey. They are really tough to break or screw into.

I've taken some of pictures of where I think my damp proof course is. That ridged line?

One picture of part of my external wall showing that the rendering seems to go down to the ground (earth), which I don't think it should.

What do you think?

I don't think the damp proof course should have been rendered over.

I don't think the rendering should have been applied all the way to the ground.

Perhaps over the decades the earth has been allowed to "grow" up the rendering and should have been periodically removed?

What do we do next?

stuart45

You've probably got dense concrete blocks on the exterior skin. The NHBC don't recommend render below DPC, but allow it if necessary provided a stronger mix is used with sulphate resisting cement and a waterproof additive.
It was probably rendered for cosmetic reasons to cover the blocks.