Dallas Harris, a homebuilder in Wrightsville Beach, N.C., decided to "rethink the intellectual way to build a house." By surveying homeowners preferences on various wall assemblies and finishes, he found that exposed aggregate exterior panels (or "pebble walls") with gypsum wallboard on the interior, were preferred over stucco and wood siding. John R. Andrews, a Wilmington, N.C., consulting engineer was called to do the structural engineering design work. The resulting wall system incorporates reinforced concrete, rigid insulation and gypsum wallboard, supported by pressure-treated lumber nailing strips. The design can withstand 110 mph winds, and exceeds an insulation factor of R 16. Panels are constructed on-site and then tilted up and welded to the foundation and to each other, requiring no skilled carpenter labor, very little time, and virtually no lumber. Even with interior walls and roof trusses constructed with dimensional lumber, the homes use approximately 50% less lumber than traditional frame constructions. Harris' average construction time was six weeks per house.