Porch walls issues! Damp? Efflorescence?

[Djomidlands]

Hi all, my porch wall had slowly got into the below state, a year after painting the walls with contract Matt paint. Scrapped off the worst of it today. Wall doesn’t appear wet. I’m thinking of using some plaster repair on it and paint with some masonry paint I have in the garage. Any thoughts on whether this is okay?

Also, any thoughts on why the floor looks the way it does? The floor appears to be tiled, but has hundreds of these tiny holes in it.

Photos of the tiles beneath the Matt which is currently down. Porch built early 70s.

Thanks

 

[Koolpc]

Penetrating damp.

Pics of outside.

Is it single brick or cavity?

 

[Djomidlands]

Penetrating damp.

Pics of outside.

Is it single brick or cavity?

Think there’s a cavity. The worst is on this corner (opposite of wall). Thanks

 

[JohnD]

Please stand back and take a wider pic of the whole wall, top to bottom, inside and out, including the roof, gutter, downpipe, drain and paving.

A tip:
Include something to show scale in your photos.

How is it ventilated and heated?

Is there an internal door?