Discovered damp, what do I do next?

[MrAlyakhin]

We decided to paint the front bedroom today as it was looking a mess. Pulling some furniture away from the walls and it's clear we have some damp patches on the two external walls.

Our house is built on a slope so on the external wall where the damp is most extensive and obvious it's effectively the first floor. The less obvious damp patch is on the adjacent wall. But the base of that wall is above the patio. Part of the room is above the heated garage, the wall that's damp is above the non heated part of the garage. I've just realised the humidity in the whole room is very high. I'll put the dehumidifier in. The patches are all 2/3 feet from the floor. The paint there is peeling and flaking off.

The house was built in 1970. It has a cavity and stone cladding. Not sure if it has cavity wall insulation or not.

I'll get the gutters cleared but what do we do next?

Do you rent or do you own? Because there are different options available to you.

I own, so have to sort it.

Are the damp patches under window areas? We had this and turned out we needed to repair the external window ledges as they had cracks and chunks out of the concrete ledges which caused water to trickle down when it rained. The fact it’s on first floor not ground floor makes me think it could be worth investigating this, but only of course if it is under window areas!

Not under the window. That part of the room is fine. But it's also where the radiator is too? so maybe less likely to be obviously damp.