It is in showers, behind walls, and deep in linen closets. It is black and slimy, white and fuzzy, or green and spongy. It is making homeowners struggle to breathe and costing them millions in repairs and healthcare bills, they say.

Mold is driving Americans crazy, and they want their home builders to pay.

What is more clear is that these lawsuits are long, unpredictable and exorbitantly expensive for both sides. For America’s largest home builders, they are adding to their growing legal costs and weighing on their profits as they cope with a stagnant housing market.

“The mold litigation isn’t going away,” said Tom Curran, a partner at law firm Duane Morris.

Many lawsuits pursue damages for more than the total value of the home, and in high-profile litigation involving a number of homes, plaintiff lawyers are looking for hundreds of millions of dollars from home builders.

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