Hello,
I am new to this group. I just bought a recently remodeled house,
and I have noticed that there are small sort of round dark spots on
some of the exterior walls. These spots are about 5 inches above the
floor, and they are randomly scattered. The spots are about 1 to 2
inches in diameter. It seems that they are the result of rusting
nails. I immediately considered water damage, and so I went outside
and inspected the exterior of the wall, and there is no apparent damage
at all. The part of the house that has this problem is an addition, on
a slab foundation. Based on what I can see, the guys who put this
place together cut every possible corner.
Has anyone out there ever dealt with this before? Is this an
indication of interior water damage. Or could the rust be from a one
time wetting event, such as painting?

thanks
flank

It might be the nails get cold in winter and condense, maybe there is no
insulation in the wall.

Flank wrote:
Hello,
I am new to this group. I just bought a recently remodeled house,
and I have noticed that there are small sort of round dark spots on
some of the exterior walls. These spots are about 5 inches above the
floor, and they are randomly scattered. The spots are about 1 to 2
inches in diameter. It seems that they are the result of rusting
nails. I immediately considered water damage, and so I went outside
and inspected the exterior of the wall, and there is no apparent damage
at all. The part of the house that has this problem is an addition, on
a slab foundation. Based on what I can see, the guys who put this
place together cut every possible corner.
Has anyone out there ever dealt with this before? Is this an
indication of interior water damage. Or could the rust be from a one
time wetting event, such as painting?

thanks
flank

Yeah, could be condensation. Could be moisture wicking from the
surrounding ground. Is there a sprinkler that sprays in the affected
areas? Or do the areas hold moisture?

It is an odd problem. One wall does have a sprinkler spraying nearby,
but the other two walls don't. And one of the walls is a shared wall
with the garage, and so it is not even an exterior wall. So, let's
consider the wicking moisture/condensation problem. Why would the rust
spread out to a circle of 2" diameter? Does that seem right? It seems
to me that the rust would stay isolated to the nail head, or it may
streak down the wall like nails in a fence. I don't understand why the
rust spot should spread. Any ideas?

flank

Hopkins wrote:
Flank wrote:
Hello,
I am new to this group. I just bought a recently remodeled house,
and I have noticed that there are small sort of round dark spots on
some of the exterior walls. These spots are about 5 inches above the
floor, and they are randomly scattered. The spots are about 1 to 2
inches in diameter. It seems that they are the result of rusting
nails. I immediately considered water damage, and so I went outside
and inspected the exterior of the wall, and there is no apparent damage
at all. The part of the house that has this problem is an addition, on
a slab foundation. Based on what I can see, the guys who put this
place together cut every possible corner.
Has anyone out there ever dealt with this before? Is this an
indication of interior water damage. Or could the rust be from a one
time wetting event, such as painting?

thanks
flank

Yeah, could be condensation. Could be moisture wicking from the
surrounding ground. Is there a sprinkler that sprays in the affected
areas? Or do the areas hold moisture?

Flank wrote:
Why would the rust spread out to a circle of 2" diameter? Does that seem right? It seems
to me that the rust would stay isolated to the nail head, or it may streak down the wall like
nails in a fence. I don't understand why the rust spot should spread. Any ideas?

I'm not sure I have a good response. Rust spots bigger than the nail
head aren't uncommon -- I've seen them in bathrooms with lousy
circulation. I could see relatively large spots if the moisture is a
repeat problem (ie, if there was a one-time moisture problem I'd
probably expect smaller rust spots).

For rust to run down, it seems there would need to be so much moisture
that it reaches or passes the saturation point (given that the moisture
is coming from the outside or the bottom). A fence gets rained on and
water runs down -- the water carries the rust down.

Is the room in question on a slab? If one of the trouble walls is not
even an exterior wall I'd look at the slab. Maybe someone with more
experience will comment, but that seems like a lot of wicking moisture.
I dunno.

The easy thing to do right now is to make sure the ground is sloped
properly to allow drainage, and to make sure the soil/mulch is not in
contact with the walls outside.