A pair of WSJ articles imply that some McMansions were built fast but poorly during the housing boom.

Cracked Houses: What the Boom Built (subscription)

"... hundreds of thousands of people from California to Georgia say their almost-new homes need costly repairs because of construction defects. The furious pace of home building from the late 1990s through the first half of the 2000s contributed to a surge in defects, experts say. It caused shortages of both skilled construction workers and quality materials. Many municipalities also fell behind inspecting and certifying new homes."

Blue Oaks Estates, in Rancho Murieta

"... was built on clay soil that expands in the rainy season and contracts in the scorching summers, ... This is damaging the homes' foundations and subtly twisting the frames, causing homes to slowly pull apart--as evidenced by cracking floors, walls and ceilings, separating gutters, and jammed windows and doors."

The article notes that other Rancho Murieta homes, "built later with different types of foundations" are holding up better, but that spooked lenders are requiring a "$7,000 engineering study" before refinancing in that area. In my experience, geotechnical reports and structural engineering fees pay for themselves. Even if there is no clay, ground that seems pristine may have been a dumping area decades ago. If so, builders have to remove the loose fill and carefully replace it with controlled fill, or extend foundations deep into original soil, or both. Home builders don't always want to pay for such reports, but because they didn't build for clayey soil, the Blue Oaks builders repurchased 50 homes, installing drainage systems, and underpinning foundations before running out of money.

Chinese Drywall: Pinpointing the Problems (subscription)

"The U.S. Consumer Product Safety Commission in recent months has received more than 550 reports from people in 19 states and the District of Columbia involving odors, health symptoms and corrosion problems they blame on imported Chinese drywall. The complaints involve "rotten egg" smells and corrosion of wiring and other metals in the homes."

...

"Homeowners who believe they have Chinese-made drywall have complained of itchy eyes and skin, runny noses, nosebleeds, headaches and asthma attacks, among other things."

There seems to be too much sulfur in the Chinese wallboard (drywall is a US brand name, that, like kleenex, has become generic in the building trades), which slipped into the market during the housing boom, but no one is sure why just yet. The EPA has even found high concentrations of strontium in the Chinese products.

Along with aging infrastructure, Americans will have to be wary of shoddy construction and suspect materials in the years to come.