What was the waterproofing plan for the basement exterior?

"Should I be worried? Or is this type of mold common in new construction?"

Mold is not common in new construction. I'd be more than a little concerned at this.

I think the mold is cause for concern. The notion that it will be "wiped off" suggests a naivete about mold. Like Frank and Frank, my concern would be the exterior waterproofing of the foundation. I'll add two more: 1.) are the gutters and downspouts installed and directing storm water away from the foundation? and 2.) what type of insulation was used on the interior foundation walls?

No climate control I’m not surprised the basement is damp…

To be sure, climate control is critically important in a finished basement. The HVAC system needs to be operational when finishes are installed (it can be turned off when sanding drywall or any dusty work which would get in the air handler and duct work.)

If the mold were uniformly dispersed on the drywall, it would implicate the lack of climate control, but it may not be the root cause of the problem. The fact that mold appears to be limited to an area within two feet of the bottom of the wall suggests a foundation waterproofing issue to me. Getting the HVAC system operational may reduce the potential for mold growth (most basement HVAC systems don't adequately dehumidify,) but the root cause needs to be addressed to ensure the problem doesn't recur.

Once mold/mildew is established it's darn hard to get rid of. If the builder thinks otherwise, he's about to get a lesson.

Thank you all for responding! So the gutters and downspouts have not yet been installed. I'm told that will be happening soon. Final grading has also not taken place yet, although they have done the initial grading. I've attached a picture I took last summer before they backfilled the foundation with gravel and dirt. The black paint was a thick rubber like material that was sprayed on the exterior foundation walls and then the insulation was applied (see attached picture - sorry I don't know what products were actually used). The interior basement walls were insulated with R-13 faced fiberglass insulation. The builder did bring over a heavy duty dehumidifier yesterday and the basement felt less damp after just a few hours. This finished space with the visible mold sits next to our unfinished basement. About six weeks ago we did notice that the basement wall was wet (picture attached is the unfinished space that sits next to the finished room where we found the mold). When we brought it up at that time, the builder said it was just because we didn't have gutters and downspouts yet and not to be concerned. Obviously fast forward six weeks and now I see that we do need to be concerned. Does the drywall and insulation need to be removed in that room? Do we need to contact a mold remediation company? I appreciate your help!

Managing storm water at the surface is important. Proper grading coupled with gutters and downspouts will go along way to reducing the amount of water in proximity to the foundation. That said, you need to have a means of dealing with water that flows along the foundation wall and down to the footing level. Typically this involves installing a perforated drain pipe that discharges to daylight or to a sump pump. Backfill material should be selected to provide a capillary break and promote the flow of water to the drain pipe instead of the foundation wall. I can't tell if you have those from your photos; at least with my elderly eyes.

Thank you! I was looking at earlier picture that I took and there are drains on the interior and exterior of the foundation. Those were then covered with gravel. The space surrounding the foundation was backfilled with gravel and then dirt.

Though it meets Code, fiberglass alone is a poor choice for interior basement insulation. Unforgivable in a custom home.

Building Science Corp.

If it were my build, I'd remove that section and check what happened.

FWIW, I run a dehumidifier in the basement as soon as it's insulated and power is available.

"Though it meets Code, fiberglass alone is a poor choice for interior basement insulation."

Amen.

You can see holes in the piping in the upper portion of the top picture if you make the photo larger. It's not clear whether they used filter fabric over the piping before placing the gravel, but one can hope.