Blue mould with furry bits on my DD’s room

[Krazynights34]

I’ve just discovered this. All over the lower part of the external wall. We just moved in two weeks ago.
She has respiratory issues.
I’m freaking out.
Do any of you have any ideas what I can do?

To add, we had some damp caused by a large climbing plant anchored to wall by previous owners with pins and resultant mortar loss. Plant dug out, pins gone and remortared and it dried out pretty fast

I’m so grateful to you all! I was so scared. This child is prone to lung infections.
She’s fast asleep in our bed.
Her bedroom is going to become a hallway as soon as we can get building started (if we get planning permission of course).
We saw the house numerous times over summer with an architect (well two) and there were no signs of damp. The day we got the keys I could see slight damp spots on that wall.
I had the big spender Dfil look at it the day we moved in and he said it could be various things but wasn’t serious (he ran a company of a type that means he knows a lot about construction).
I’m so mad at them right now - but with myself more so

@Krazynights34

There’s nothing on the other side of the wall. We’ve had crazy heavy rain yesterday. I’m going to check the gutters tomorrow

There must be something. Do you mean it is an external corner, with the garden outside both walls? If so, probably guttering, as a downpipe will not be on the exact corner, or possibly roof.

Photos will help a lot.

How old is the building? A relatively modern one wil have cavity walls.

Is the floor concrete, or wood?

Wallpaper looks old enough to have used starch based paste - hence fluffy mould - though fluffy mould would take a little while to grow - at least a week.
As pp have said you wouldn't get rising damp running up the corner like that.

Check the plaster behind the damp - if its firm, not crumbling, then the stain is relatively new - if its crumbling then the plaster will have to come off anyway - not a huge job once you have found the source of the water. Also if its been there a while I'd expect the skirting to have swollen/softened and it doesn't look like that.

As pp have said it does look like its flowing down - does gutter/external pipe leak against the wall when its raining heavy?

Is this an end corner of the house - if so then it could be associated with failed pointing letting water in when the rain is heavy enough.

oh and does the room smell mouldy/damp -

I've a similar issue and it previously was in two walls of my home.A garage extension had been built on and the dpc was breached in both corners. Another suggestion is that the wall ties are dirty/covered in rubble of some sort.
One wall was knocked down as part of some other work, one bedroom wall still causes issues and I need to get a new dpc installed. I'm using a dehumidifier in the room and just observing it for a while. I decorated the room recently and there's definite evidence of a tide mark of salts on the wall. Mentioning damp in a house seems to have builders rubbing their hands in glee but I will need to get it fixed.