Damp on exterior wall - what is the cause?

[Pamela1]

Hello

This is my first post on this forum and I am hoping somebody would be able to give me some advice.

I painted the exterior courtyard wall (to the back of my house) approximately 5 years ago with masonry paint but small bubbles appear between the paint and the wall.

I am sure this is to do with damp but do not know what the source is. Could it be water penetrating the wall (see the slates on the top of the wall) and I need to get the render between the slates rendered again? Or could it be rising damp?

I have tried to post some photos but it says the maximum allowed is 100 KiB but mine are all below this size so I presume this restriction is because I'm a new member?

Thank you for any advice.

[stoneyboy]

Pamela1,
Yes it's very likely to be damp and you need to find the source.
If the wall is a retaining wall the damp will be penetrating through the wall.
If you've just painted one side of the wall the damp may be coming from the unpainted side.
If the bubbles are in the lower 1 metre of the wall its rising damp possibly due to there being no DPC.
If the slates on top of the wall are sound you could try treating the top of the wall the a silicone liquid.
end