# water stains on drywall. advice?



## thekingofboggle (Apr 2, 2012)

Hello I just noticed these stains on the wall. They are on the second floor of an exterior wall in a 1950's semi bungalow. Is this a sign of moisture behind the wall? should I cut open the section of drywall to see what is causing the staining? 

The stained wall is perpendicular to a knee wall. I had a look inside the space behind the knee wall and noticed the nails holding up the plywood in the ceiling of that space looked strange. Do the nails in the plywood look that way because of moisture? is this related to the staining?

any advice is appreciated,
thanks


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## Maintenance 6 (Feb 26, 2008)

Looks like it took on moisture at one time or another. If the drywall is solid, then I'd coat it with a stain blocker and repaint. The stains don't look like it was a significant water event. Try to get an idea of what may have caused it to begin with and correct that. Regular drywall is not at all moisture friendly. You don't get too many chances before you need to replace it. If it isn't dried out quickly, it will turn into mold food as well.


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## Gary in WA (Mar 11, 2009)

Check other areas for excessive moisture as shown. Why is the ply sheathing nailed to the bottom of the rafters? Or ceiling joists?

Gary


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## joecaption (Nov 30, 2011)

Looks like poor ventalation to me that's causing moisture to form and causing the nails to rust. No one here is going to know what the "nails look odd" is going to mean.
Is is it rust on the nails?


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## thekingofboggle (Apr 2, 2012)

*a look behind the wall*

So I finally got around to cutting a section of drywall out to get a better look at what is going on. It looks like the water marks line up with where the drywall was nailed up. Does this mean that nails were becoming cold from the outside and then making moisture condense when it got to the warm air inside? if so, is there something I can do about this? maybe coat the nails in something?


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## joecaption (Nov 30, 2011)

It may be a big help if you would take the time to go back and edit your profile and add where it is you live.

Were all going to be interest to find out why it looks like there's plywood behind the drywall. A shear wall if your in CA?

Any roof needs soffit vents, some form of roof vent (a ridge vent in most cases works best) and a clear way for air to make it from the soffit to the ridge vent to draw hot moist air out.
If not all that moist air is traped behind that knee wall.


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## Maintenance 6 (Feb 26, 2008)

Looks like spray foam to me. I would have coated the area with stain blocker and waited it out to see if it reoccurred. Especially since it was a very limited area.


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## thekingofboggle (Apr 2, 2012)

my apologies for not filling out my location. I'm in Alberta, Canada. It's looks like mdf in behind the drywall. I'm not sure why it is there.

the plywood is nailed to the ceiling joists on the other side of the knee wall. it's a sort of attic space. there is some plumbing that goes through this space so I am guessing the plywood is a way of sort of making it a finished space.


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