What could cause this rusty nail

[Ken Rowe]

A person called me today and asked what could have caused this. The nail was driven into an upper bedroom, exterior wall to hang a picture. Less than a week later they pulled it out and found this.

The house was built in 2006. Unfinished by a builder who went bankrupt. They bought the home and finished it and moved in two weeks ago. Since they've moved in their young son has had respiratory problems.

I'm thinking Chinese drywall (very rare here in MN) or wet insulation in the wall.

I didn't inspect the home but may be looking at it tomorrow.

[JB Thompson]

Well my first thought too was chinese drywall. Either a moisture issue in drywall or insulation... or some chemical reaction issue.

Take a rake when you go tomorrow and pull back the insulation in the attic.

[chris mcintyre]

I'm thinking Chinese drywall (very rare here in MN) or wet insulation in the wall.



My vote is for wet insulation, if the nail was for hanging a picture the rusted part is about what I would expect to see penetrated through the drywall (if I could see through the wall :)).

[Nick Ostrowski]

I have no experience with any Chinese drywall issues but I guess you can't totally rule it out unless you can see the manufacturer stamping on the other side of the drywall. Otherwise, I'd lean towards unseen moisture in the wall cavity.

[Scott Patterson]

Mu vote is for a wet wall. The end of the nail was hopefully in a stud. Also with problematic drywall the entire nail would be effected. Also with the problematic drywall you do not usually see rust as a condition of it.

[H.G. Watson, Sr.]

Bet they're running AC, nail to hold a pic likely pointing up in the room.

Outside wall warm, cool inside, nail cold. Condensation at dew point, runs down, then wicks, untreated/coated nail tip coated with gyp board and drywall mud, water, little air, reacts. What type metal contact (if any) was "hung" on this barely penetrating nail on the room side?

Been a hot humid week with the house closed up? First time actually running system lower temps full-time with house closed up since just finished?

Might want to clean the coil and sanitize the condensation pan and line. Might also want to have the ducts

Use brass/coated picture hanging hardware.

Suppose if using such a nail in such a way might have grabbed a nail out of a catch all can and was already rusty on the tip.

[Ken Rowe]

He called me back a little while ago. Apparently he cut a hole in the drywall and found the insulation is saturated. Today was an extremely hot and humid day, 95 degrees with a dewpoint of 78. However, we've also gotten about 5 inches of rain in the past 3 or 4 days and the nail had been under a window.

No, the nail wasn't in a stud, but did penetrate the vapor barrier. He said the studs were dry.

He was going to give his father ( a contractor) a call and let me know if he wants me to take a look at it.

[Scott Patterson]

He called me back a little while ago. Apparently he cut a hole in the drywall and found the insulation is saturated. Today was an extremely hot and humid day, 95 degrees with a dewpoint of 78. However, we've also gotten about 5 inches of rain in the past 3 or 4 days and the nail had been under a window.

No, the nail wasn't in a stud, but did penetrate the vapor barrier. He said the studs were dry.

He was going to give his father ( a contractor) a call and let me know if he wants me to take a look at it.

Time to open the walls up, find the leaks, dry it up, replace the insulation and drywall! They have a mold farm growing in them there walls!

I just had another thought.....

Do they have a wind barrier (plastic or Mylar sheeting) on the drywall side of the studs? I know this is popular and common up north but it also locks everything inside and can make the stud cavity like a rain forest!

[Ken Rowe]

Just got back from looking at it.

The cavity he had opened is on the main floor, under a walk in closet's window. The cavity in question goes from the floor to the bottom of the window, 20" or so. The construction is 1/2" drywall, plastic barrier, 6" fiberglass batt insulation, fiberboard sheeting, Tyvek house wrap, and Hardi plank siding. The plastic barrier is wet on the insulation side as is that side of the insulation. The fiberboard shows no staining and the insulation is not wet on the fiberboard side.

There is an HVAC duct on the floor directly below this area, blowing on the suspect area of wall. They've been keeping the main floor at about 70 degrees, however the upstairs was about 80 degrees. Temperatures this past week have been in the 90's with 70+ dewpoints. It does not have zoned heating. The HVAC distribution does not have dampers to regulate the basement, main floor, or upper level independently. Instead the dampers control East and West sides of the home. The home is approximately 4500 square feet.

The Hardy plank siding has no flashing or caulking at the butt joints, just open to the Tyvek. The window have a 5" Hardy plank trim all the way around. No drip caps at all. No flashing on the interior corners of the siding.

To me it looks like a serious condensation problem, but can't discount the improperly installed siding. I referred him to a moisture specialist.

His father, a building contractor, performed the inspection.

[Ken Rowe]

Do they have a wind barrier (plastic or Mylar sheeting) on the drywall side of the studs? I know this is popular and common up north but it also locks everything inside and can make the stud cavity like a rain forest!

Generally condensation does not form on the wind barrier once the drywall has been installed. However, with no drywall and a source of conditioned air the interior will get wet. Never have an open a/c duct in an unfinished basement that has the plastic barrier. In this case it looks as if the condensation formed even though the drywall was in place. Something that shouldn't happen and I've never seen before.

[Scott Patterson]

Generally condensation does not form on the wind barrier once the drywall has been installed. However, with no drywall and a source of conditioned air the interior will get wet. Never have an open a/c duct in an unfinished basement that has the plastic barrier. In this case it looks as if the condensation formed even though the drywall was in place. Something that shouldn't happen and I've never seen before.

I have seen many homes in the South that were built back in the 1980's when for some unknown reason the NAHB was pushing their members to put in a wind barrier (plastic sheeting) over the studs and insulation. It turned the walls into an H2O producing machine!

The outside summer heat warmed the brick/siding and the wall cavity then the nice cool interior cooled the plastic and POOF we have condensation forming between the plastic and the insulation. The problem is accented when faced batt insulation is used. With unfaced it was not that bad but it still was a problem.

[Ken Rowe]

I have seen many homes in the South that were built back in the 1980's when for some unknown reason the NAHB was pushing their members to put in a wind barrier (plastic sheeting) over the studs and insulation. It turned the walls into an H2O producing machine!

The outside summer heat warmed the brick/siding and the wall cavity then the nice cool interior cooled the plastic and POOF we have condensation forming between the plastic and the insulation. The problem is accented when faced batt insulation is used. With unfaced it was not that bad but it still was a problem.

It's required here with the Energy Code. This was unfaced insulation. Here you can't use faced with a wind barrier. But as I've said, I've never seen an issue with condensation when the drywall is installed. This year has been very wet, hot and humid though.

They also had an air exchanger in the home, set to the "summer" setting.

[Scott Patterson]

It's required here with the Energy Code. This was unfaced insulation. Here you can't use faced with a wind barrier. But as I've said, I've never seen an issue with condensation when the drywall is installed. This year has been very wet, hot and humid though.

They also had an air exchanger in the home, set to the "summer" setting.

There are several things I do not care for in the energy codes. Wrapping the house in plastic is one of them. Oh well what is one suppose to do but abide by the one size fits all energy code... :)