Fannie Mae wants to get a better idea of how many of its properties may contain defective drywall. The government-sponsored enterprise advised all networked brokers, listing agents and asset managers to review all inventory. "Thoroughly document any evidence of potentially defective drywall," the note from the GSE states. Fannie Mae also requires relevant personnel to take a training course for identifying defective drywall. Everyone who works with Fannie at this level must complete the course by Oct. 31. The GSE owned 135,000 properties at the end of the second quarter. "All properties that may have defective drywall will no longer be listed until further review of the property can be made," according to Fannie's note. The new method for identifying defective drywall is in line with current guidance from the Consumer Product Safety Commission. Fannie Mae does not name a specific producer or country of origin for the defective drywall. However certain shipments of drywall from China proved to be highly corrosive to building materials. Domestic drywall also faces scrutiny. Residents of properties with defective drywall complain of corroded pipes, for example, as well as respiratory ailments from exposure to the products. Write to Jacob Gaffney. Follow him on Twitter @jacobgaffney.