Patching and Plastering - Re-occuring bubbling on bathroom wall

I have a bathroom wall (plaster) that had odd bubbling. A little on the ceiling and one wall (by toilet), no water stains but similar to a half moon shape, one area more condensed (no obvious pattern). I had a professional come in and repaired it, his thoughts were it wasn't water damage (i.e. roof leaking, stink pipe etc.) A note though, there was a lot at the stink pipe location. Well a year or so later, it's occuring again.

I've done a little investigating and wanted others thoughts as well. The ceiling fan only vents into the attic and not through the roof, it was also obstructed by a roll of left over insulation ... could this cause a moisture issue, enough to create the plaster to bubble ... then why only in the one wall? :confused:

The stink pipe doesn't appear to be leaking at the roof, so i'm stumped and wanted some advise before a second repair is performed. I can post images if you think it would be helpful.

Any Advice is much appreciated.

Welcome to the forums!

Pics are always nice - use a free site like Image hosting, free photo sharing & video sharing at Photobucket (http://www.photobucket.com)

The exhaust fan is always suspect because if the moist air from showers isn't removed, it will lay on the walls/ceiling with the potential for problems. Removing the obstruction should help a lot although it is best to finish piping it to the exterior [either roof or gable] What type of paint do you have on the walls/ceiling?

I used a interior latex paint, i also primed prior to painting. I'll post a picture tomorrow; if you have time ... please take a look.

Many friends i describe this to keep assuming the roof/stink pipe is leaking but i would think i would see more water stains or obvious signs other then the plaster bubbling.

Again, i'll put up a few pics and tell me what you think

Thanks again for your time.

Here are a few images

This is center wall after i peeled away some paint

http://i46.photobucket.com/albums/f110/paka8919/Bathroomwall4-09012.jpg


Here's one top at ceiling

http://i46.photobucket.com/albums/f110/paka8919/Bathroomwall4-09006.jpg


Here's the top one again after paint removed, the plaster is very crumbly/loose

http://i46.photobucket.com/albums/f110/paka8919/Bathroomwall4-09013.jpg

I did go in the attic and there's no signs of water entering from above :confused:

The wall was completely repaired roughly 1 1/2 years ago from a similar situation :wall:

Looks like water damage. Is there a cast iron drain pipe coming down from the second floor? May be a leaking fitting. If one story, the rain water is running down along the pipe to the wall. On a dry day spray water on the roof at the pipe, with someone in the attic with a light. The exhaust from the fan could be condensing on the colder pipe, then running down to the wall. Be safe, GBR

I couldn't tell if you used latex flat or latex enamel - enamel is always better for bath rms because it will repell moisture. That said, it does look like the mositure is coming from behind:eek:

What is above this room. Attic? does the roof line come down on top of the wall. Its definitley water damage but not enough to do significant damage. If it was you would be able to poke your finger through the wall.

There is an attic above, i went up there to inspect for any water entering by the stink pipe. I didn't see any obvious signs of water leaks. The pipe goes into the attic the makes a 90 degree turn for about 4 feet the up and out the roof.

The roof line doesn't meet at the top of the wall, there is complete access above the bathroom, just the typical roll insulation in between the beams

The wall areas that are bubbling are not "mushy" still hard but if you probe into it like i did in the images it crumbles, feels like very fine salt, almost flour like. To answer the question, NO i can't poke my finger through it.

What about rain water entering the pipe, collecting where the 90 degree turn is & causing the pipe to sweat at times? Is that possible?

I had that thought also, but i didn't think enough moisture could build from the pipe sweating. Although it seems to take a period of time before the wall is showing these signs.

What does it take to put a cap on it?

Great answer ... pennies. I'll do that.