mold question

[Jmeng1026]

I was asked to inspect the structural components of a basement that flooded several years ago. The house has sat vacant for the last few years and now someone's trying to restore it.

While I was there I noticed along the bottom of the foundation wall there was a black line and the concrete had a whiter color to it below the line.

I was told the water flooded the basement up to the top of the concrete so the water was supposedly much higher than the black line.

Is the black line and whiter color concrete mold?

 

[XR250]

Why wouldn't the mold go all the way down to the slab? Could just be discolored from stuff floating near the top of the water. I suppose they could have it tested if it seems like an issue or try to remove it.

 

[ANE91]

That line looks like it could be a stillwater mark, which is what you’d use to establish the height of flooding. Time to start questioning what you’ve been told. How long did the basement stay flooded? How’d the water get out?

Re: mold, how can you render an opinion about mold without lab-testing a specimen? Ask an industrial hygienist. Structural engineers don’t know jack about mold. We can tell you if a structure is deteriorated. Decay producing fungi can affect the mechanical properties of wood, and there are specific instances in the case history of biogenic attacks on concrete.

 

[Jmeng1026]

Supposedly the water got up to the wood sill plate and studs and was coming out of the windows because the house was vacant and a neighbor saw the water coming out. Sounds like it was flooded for a month or so.

I was told the incoming water line broke and filled the basement.

I have advised the owner to contact someone who has experience with mold and knows what they are doing.

 

[gte447f]

What you see in the photo is not mold, and it is not a water mark from standing water. I am not sure of the exact cause, but I have seen similar conditions. In fact, the concrete curb upon which the wood framed walls are constructed in my own residential garage looks similar. The concrete curb around the perimeter of my garage has progressively turned white over the years (15 years). The floor slab is still a more gray color typical of concrete. The white concrete is not chalky or dusty and does not seem to be noticeably softened (cannot be easily scratched with a nail). My theory is that the white color change is being driven by some sort of environmental exposure factor, maybe either elevated moisture from the soil subgrade or maybe carbonation from CO2 in the air.

In the case of the OP's photo, the fact that the white color is limited to the bottom of the wall could lend itself to an explanation related to soil moisture. Another possible explanation might be a pour joint between two different batches of concrete used in the wall, one being more susceptible to whatever is causing the white color than the other. Just a theory.

 

[LittleInch]

If it was mold it looks like it isn't live anymore, but ultimately why do you care for a structural assessment?