We just finished our bedroom about three months ago. Now on the wall and around the ceiling I'm noticing the paint is bubbling and in some spots I see a few small cracks. This was an area where the roof originally leaked and this whole area had to be re-plastered. So, it has a history but to the best of our knowledge it was fixed.

The cause of this is either one of two things: 1) Because we didn't prime the mudded areas underneath the paint or 2) We still have a leak.

Which brings me to my question:

What's the best way to determine if this is being caused by water damage behind the plaster and paint? My thought was to put dry sponge in the addict above the wall to see if it gets wet during the next rain.

Any other thoughts?

 

Is there any staining where the bubbles are? When water leaks thru walls/ceilings it tends to leave a brown stain. Have you tried popping the bubbles to see if there is any water in them? Does the wall feel solid?

It probably doesn't make a difference but do you have plaster or drywall?

I don't think shoving a sponge down an addict's throat will help you much probably not needed in the attic either

 

Given that you had a moisture problem in the past, I would proceed with the idea it's likely moisture again.

Do you know where exactly the leak was before so that you can verify nothing is coming in there now?