Zoning laws and building codes have long recognized the inherent risk of constructing structures in close proximity. For example, the 2006 International Residential Code (IRC) requires the exterior walls on houses built within five feet of the lot-line that separates adjacent dwellings to have a one-hour fire-resistance rating. There are many ways to meet these requirements, but one of the most affordable is to use fire-resistance-rated gypsum sheathing as a component part of a system that provides the one-hour rating.