It's called split face block, a type of concrete used for exterior walls.
More than a dozen homeowners dealing with split face block problems contacted by ABC 7 for this report refused to talk on camera because they say talking about this hot button issue might hurt their home values.
"It's embarrassing, you know, you spent all this money on a home and look at it, look what's happening," said one homeowner.
It's the topic so taboo for Chicago homeowners that many won't talk about it. One West Side resident wanted to remain anonymous.
"We weren't sure exactly where the water was coming from," he said. "You start seeing the drywall starting to peel, you know, it's disappointing .. You'd actually see the nails and the two by fours, you wouldn't need a stud finder, you'd see them right through the drywall.
Home inspectors say the problem is split face block, a concrete building material used all over Chicago in brand new homes built during the latest building boom.
"I'm very scared," said home inspector William Decker.
Decker has been dealing with the problem for years.
"For the last four or five years, the major problem we saw was water coming in, and mold, and stained walls," said Decker.
But now, he says, during his inspections he's seeing a much bigger, more dangerous problem.
"This material is really not suitable for use in Chicago," said Decker. "It's too absorbent."
The block sucks up water like a sponge. The water spreads, soaking the beams holding up the roof. Then they rot.
"I've seen some that you can put your finger through them they're so soft, the weight of the roof just breaks them off," said Decker. "Come this winter, especially with the snow loads we're used to in Chicago, I'm very concerned."
"You couldn't have convinced me five to seven years ago that I would be seeing the stuff that I am now seeing," said Kurt Mitenbuler, another home inspector.
Mitenbuler says moisture problems caused by split face block can cause building supports to fail.
"I honestly think that in some of the worst buildings, we could see failures of the floor platform where you actually had a pancake failure, where it's just like boom boom boom boom. You know the floors just collapse, the top floor goes, you know? In other words, catastrophic failure," said Mitenbuler.
The Chicago Department of Buildings says "when properly constructed and maintained, split face block does not cause a safety threat to the structure or occupants of the buildings."
For companies like Seal Chicago, trying to fix split face block is big business.
"The most common call is that they've got water on the interior walls or the ceiling," said Tim Gimza, Seal Chicago.
Now, homeowners are having their exterior walls sealed hoping to stop the water from soaking in.
"There are hundreds and hundreds, maybe thousands of buildings built with this and it's either an issue now or it will be soon," said Gimza.
A spokesman for the Chicago Department of Buildings also says they have had no reports of damage to roofs due to poorly constructed walls.
A building trade association recommends that contractors make sure to install split face block properly to avoid water issues. Sealing the split face block can help prevent moisture from getting in, but some sealants have to be reapplied every five years.
Ultimately, inspectors say the only real way to completely fix the problems with split face block is to tear it out and replace it, but it could be expensive, at a cost of tens or hundreds of thousands of dollars.
