I am having a new home built. 2x6 walls. The builders have placed the walls over the floor edge 1". That meaning the 2x6 board overhangs about 1/2" as does the OSB 1/2". Is this a good method of placing exterior walls? Doesn't this changed to squareness and the roof trusses? Why are they placing the walls out over the floor? They are also putting 1" styrofoam over the floor rim board to even out the wall. Please help.