Pull on your sterile gloves, adjust your respirator, and take cover behind your legal counsel. It's time to do battle with the building industry's equivalent of the black plague... By Matthew Power

Certain design choices provide an almost guaranteed chance of moisture problems over time. Avoid these common but risky designs.

Death valley: Building side-by-side townhouses that share a valley funnels water to where it can do the most harm.

Splashdown: Combining mismatched eaves above a window can result in water cascading over window flashing. Pay careful attention to where eaves and valleys dump precipitation, otherwise, mold may gain a long-term foothold.

Bass ackwards: Even experienced subcontractors often install housewrap, step flashing, and membranes from the top down (instead of the bottom up, as is proper) so that they actually catch water and trap it behind exterior finishes. Check their work.

Airlock: Only one side of any exterior wall should include an airtight vapor barrier. By using polyethylene on interior walls, for example, and taping foam exterior panels, any moisture caught in the wall cavity stays put--and gives mold a warm, cozy place to grow and raise a family.

Fast, but foolish: Wet spray cellulose insulation typically goes in at about 25 percent moisture content. Subs must not cover cavities with drywall until the moisture level of the insulation has dried to 15 percent. Depending on relative humidity and temperature, this can take anywhere from 2 to 30 days. Back to MOLD