Thread: Dark spots on the foundation.

Hello,

Today I inspected a house built in 1997 with a concrete foundation.
My client decided to remove an insulation sheet and I noticed a dark coloration on the foundation.
I thought about glue or something...

Can anyone tell me what that is?

Thank you

Eli Smith

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Looks like mold

Moisture was likely trapped behind the insulation.
Could also be moisture seeping through the concrete wall, but not as likely.

Now, what do you recommend be done (if anything)?

Originally Posted by Rick Cantrell

Looks like mold

Moisture was likely trapped behind the insulation.
Could also be moisture seeping through the concrete wall, but not as likely.

Now, what do you recommend be done (if anything)?

Agree,
but investigation into the source of moisture seems appropriate, but that's work for someone else to do.

Originally Posted by Lon Henderson

Agree,
but investigation into the source of moisture seems appropriate, but that's work for someone else to do.

Looks like you found mould growing on the concrete.... Now it is time to figure out why it is growing on the wall and have that taken care of. One thing you can bet is that you will find the same thing in other areas...

Originally Posted by Rick Cantrell

Looks like mold

Moisture was likely trapped behind the insulation.
Could also be moisture seeping through the concrete wall, but not as likely.

Now, what do you recommend be done (if anything)?

Hey Rick,

thanks for the reply,

I was actually worried about it being mold... I have not seen much of these cases, but I will recommend the buyer to contact a professional company in order to disinfect the foundation and make sure the mold does not penetrate deep into the foundation. I don't want to take any chances since the foundation is in question.

Do you think I am going too hard on this case? Is this the kind of work the buyer can do himself, should I recommend him to wash it without calling a professional company?

Let me know what you think.

Originally Posted by Scott Patterson

Looks like you found mould growing on the concrete.... Now it is time to figure out why it is growing on the wall and have that taken care of. One thing you can bet is that you will find the same thing in other areas...

Hey there,

The source of moisture is already known, the french drain was changed last year, it was blocked because of iron ochre. Also, the water level in the sump was way too high during the inspection, which means water stays around the foundation constantly. I already recommended to lower the water in the sump by adjusting the pump and ask for the bill and guaranty concerning the french drain. Modifying the slopes will also be in my report.

Mold for sure, were there was an air space behind the wall covering, warm and cold air should not meet

Originally Posted by Eli Smith

Hey Rick,

thanks for the reply,

I was actually worried about it being mold... I have not seen much of these cases, but I will recommend the buyer to contact a professional company in order to disinfect the foundation and make sure the mold does not penetrate deep into the foundation. I don't want to take any chances since the foundation is in question.

Do you think I am going too hard on this case? Is this the kind of work the buyer can do himself, should I recommend him to wash it without calling a professional company?

Let me know what you think.

Once the source of moisture is eliminated, then clean up should be relatively easy. Mold won't penetrate the concrete past the surface or damage it. A basic disinfectant should clean it up. The insulation is likely a total loss.

Insufficient insulation and a poor insulator (polystyrene) and likely exposed concrete foundation above grade.

Originally Posted by Eli Smith

Hey Rick,
Is this the kind of work the buyer can do himself,

How could I know if the buyer has the experience and is capable of performing this work?
I don't, and most likely you don't know either.

Originally Posted by Eli Smith

should I recommend him to wash it without calling a professional company?

Don't recommend HOW to make a correction.
You may include links or quotes from the EPA site (or similar).

- - - Updated - - -

Originally Posted by Lon Henderson

Agree,
but investigation into the source of moisture seems appropriate, but that's work for someone else to do.

That is good advice.

There is no reason why not to tell the owner how to clean it because that information is on Canada Mortgage and Housing website.

Soap and water, or Trisodium Phosphate which can be used on concrete.

http://www.cmhc-schl.gc.ca/odpub/pdf/66170.pdf

Originally Posted by Raymond Wand

There is no reason why not to tell the owner how to clean it because that information is on Canada Mortgage and Housing website.

Soap and water, or Trisodium Phosphate which can be used on concrete.

http://www.cmhc-schl.gc.ca/odpub/pdf/66170.pdf

Originally Posted by Rick Cantrell

You may include links or quotes from the EPA site (or similar).

Quote some authority (with credit), or better to provide links to an authority.
Don't tell the owner how you think it should be done, unless you are well qualified or have time to explain in detail what to do.

Rick may be you can quote some 'credible' sources as to your stance. The CMHC site is straight forward and any inspector can quote it or repeat it to clients.

There is no reason as to not provide how to proceed or what 'options' may exist as to clean up.
Its called a standard of care. What are clients paying for?

Originally Posted by Raymond Wand

What are clients paying for?

Find defects
Report defects found
Recommend action to be taken
This is most often what type of contractor to contact
Only rarely should it be a how to.

Originally Posted by Eli Smith

Hey there,

The source of moisture is already known, the french drain was changed last year, it was blocked because of iron ochre. Also, the water level in the sump was way too high during the inspection, which means water stays around the foundation constantly. I already recommended to lower the water in the sump by adjusting the pump and ask for the bill and guaranty concerning the french drain. Modifying the slopes will also be in my report.

So if the foundation (and footing) in always wet, as I would also imagine to be wet on the inside too (under slab). I suspect water by way of capillary action is migrating up.

Unlike the rest of the structure, basements dry in. It is important that noting is done to prevent this in drying... right down to the type of paint or wall finish. It's hard to tell from the pictures, but it looks like a moisture barrier was applied on the concrete. If this barrier prevents the wall from drying in there could be problems.

So the first thing I would consider is lowering the water table. This is the most logical starting point, hopefully this make a noticeable difference. This can be done by lowering the pit or adding another pit(/pump)... or both. Unfortunately it is too late to add a capillary break between the footing and the foundation walls.

If you want to insulate that wall; I would recommend spray foam. It will not prevent the walls from drying in. If more is needed I would consider dehumidification or maybe air exchange, but there are situations were air exchange is not good.