Weird Spot on Dry wall

Hi All,

I'm very new this forum and a relatively new DIY though I've done minor home repairs since HS. (had a deadbeat dad, so gotta learn everything by myself). So pardon my ignorance.

At our house, we got these weird markings on the wall that shown through the matte paint. I can't imagine what it is but probably water that's seeped from the exterior brick wall. It's been a couple years and the markings have not increased in size, changed shaped or color. So I guess whatever has been causing it has stopped for that length of time. I'm pretty sure this is not mold/mildew as we live on the second floor and there's been no flood.

One of these markings on wall is by an electric outlet. I took out the outlet plate/cover to check the exposed drywall, and it seems to be in good shape without any obvious discoloration or brittleness. I took the outlet out itself. The outlet and the wires look fine to me. So I presume the other parts of the wall where I cannot see the cross-section is possibly of the same condition.

I know ideally I should to take apart the wall find out what the hell is going behind it. It's happend to my neighbors and they have taken their wall apart, but could not find any source of leak from the interior or exterior of the building. I rather not go through the headache of doing so and end up not finding out the cause. I probably will in the future when I finish school and get enough money saved.

My question is: Can I paint over this so that I dont' have to keep staring at this? It's quite an eye sore. I really don't want to cut out or take apart the wall (not sure how I would go about doing this anyhow).

Would appreciate any expert opinion on this.

 

Those were caused by water getting in somehow.
Could be anything from an ice dam on the roof, plugged up gutters, roof leak, someone did not allow enough overhang on the shingles ECT.

 

Appears it could be water from condensation forming on a nail that missed the stud edge, the outlet one is easy; moisture in the air going around it in a heating season; pp.10, Fig.4; http://www.buildingscience.com/docum...researchreport

Gary

 

If the water source has been stopped, you can coat the stains with a solvent based primer and then paint them. Failure to use an oil base or pigmented shellac primer will result in the stains bleeding back thru any latex coating.

 

From the rings it indicates it has occurred many times, thus painting over it will only last until the next condensation or leak event. All of the above advice is good, I go with condensation and even though it is only showing up on exposed metal surfaces, it is on the major side.

Now, condensation would happen when those nails are cold and exposed to warm moist air. A summer event would be air conditioning running and outside humid air leaking in through the brick and wall. A winter condition would be cold air or a poorly insulated area cooling those areas enough to form condensation from warm inside air leaking into the walls. The winter condition usually occurs on the interior of the exterior (colder) wall.

Do you run a humidifier in the winter?
Do you run ac during the summer?

Bud

 

I would also use some paintable caulk to seal around the box the receptacle is in before painting. No need to buy a caulk gun for what you need. One of the squeeze tubes will be more than enough.

 

Hi guys! Thanks for the input. Everyone is agreement that it is moisture.

Acknowledgement

JoeCap, appreciate you supporting my guess and thanks for the brainstorming ideas for possible sources of the water.

Gary, thanks for the input. Not surprisingly I had not considered the real possibility of humid air getting through wall and condensing on exposed/misplaced nails. thanks for sharing the research report. Surprised to see how much water drywall can absorb air gets leaked.

Nashkat, Good point on the caulk. I'll will have to check if there's a significant gap between the receptacle and sheetrock edge. It's possible that gap is much larger here that outlets of other rooms.

Bud90, your explanation is very sound. In the past (2003-2005), we did run the A/C often in the summer since it gets hot and humid. Since then we have dramatically cut down on the A/C to conserve energy (and money). However this building is very poorly insulated because in the winter we expend vast amounts of energy to keep it decently warm. However, the air is very dry and we make no attempts to humidify it in the winter. (bloody noses every now and then). So, i feel only summer a/c contributes more than winter to the spots origin.

Marks, thanks for the invaluable advice. That probably saved me a second or third paint job in the future. I have some questions....see below.

Plan:
For the time being, I got to move into this room to make space for my cousin spending the next year with us. I was going to use latex primer before painting it, but given the advice about solvent based paint then I'll use that as a stop-gap measure until I can move back to my old room as well as have time to open up the wall. Commentary: (jeez, that idea gives me the shivers...that'll take me weeks to learn by myself how to take sheetrock out and put back to together...I'm afraid it would be above my level??). Wish I had a friend who's dad knows this kinda stuff and teach me. If I do pursue this during my next summer school vacation and find out this was all due to strictly a few stupid misplaced nails, I'm going to be pissed. (maybe even enough to drop out of school to go in this business.) I could go on an rant about how people should take pride in their work...not be lazy or take shortcuts...pete's sake...people live in these places they create. Sorry...that's me.

Questions:
Anyways, For my understanding, can someone explain to me why dry water stains will bleed through latex primer or why it won't bleed through something like Kilz? I'm mean these stains are dry. What is it about latex itself that makes it a poor choice? does latex attract more water? Is there a science-y explanation to this? the Lowe's guy can't seem to explain it.

Marks, you seem to be an expert at this. had I used latex primer, how soon does the water stain bleed through the new coat of latex primer and paint? Is that length time dependent on certain factors? If so, which factors? Others folks, please feel free to chime in.

Another question for everyone, are these water stains that look like this typical
or unusual? Is the appearance by the outlet typical of moisture/condensation being trapped inside?

Sorry to ask so many questions...but a kid like me is naturally curious!

 

Nashkat, again thanks for the advice. What I means to say earlier was, "I'll make sure to caulk the box edges".

So for everyone whos replied on the thread, if you don't mind chiming in on the questions I asked, it would be great.

For anyone reading/visiting the thread and have knowledge to share in regards to the questions I asked or have opinions on my wall issue, Please feel free to share on the thread.

zepher

 

The apparent nail are not really the problem, just the part of the problem you can see. The problem is condensation is occurring inside your walls and they need more insulation and air sealing.

I notice stained natural trim at the bottom of the wall. During air leakage testing we see a leakage from behind that trim, because it never gets painted into place. If you filled those wall cavities up with water, it would pour out all over the place. Air is just another fluid and air sealing is a detailed task, like pulling trim and caulking below the drywall. So, not just the electrical boxes, but that will help.

Not a painter, but have followed that advice for many years and seen results when it was not. The stains bleed through in a matter of days.

Bud

 

How soon the stain the bleeds thru latex coatings depends on the severity of the stain and the quality/type of latex coating. I've seen stains bleed thru before the paint/primer dries or wait for a week or so. I suspect your stains would bleed thru latex primer within a day or so. There are latex primers including Kilz2 that claim they seal water stains but it's been my experience that they just slow down the bleeding process. I normally use an oil base primer but will use pigmented shellac [zinnser's BIN] if the stain looks like it could be problematic or if I need it to dry faster.

Solvent based coatings have molecules [?] that are closer together than their latex counterpart. This allows them to seal better than latex. Oil base seals better than latex and pigmented shellac seals better than oil. Obviously I'm a painter not a physicist but you get the general picture.

 

Go in the basement (unfinished)/crawlspace and seal wiring/plumbing holes below that wall, in attic also- if accessible; Energy-Efficient Building Design

More work, lol; Home Energy Magazine :: Black Stains in Houses: Soot, Dust, or Ghosts?

Home Energy Magazine - Retrofit :: Air Sealing in Occupied Homes

Why;http://www.wag-aic.org/1999/WAG_99_baker.pdf

I'll help; http://www.finehomebuilding.com/PDF/Free/021105092.pdf

Gary