ADA Tolerances Provisions

Q3.) What are the types of “manufacturing processes” that were anticipated where the advisory says “tolerances recognized by this provision include… “those that may be a necessary consequence of a particular manufacturing process”?

A3.)  This question is a bit easier to answer than the one above.  One example of a manufacturing process that would fall into this category is the manufacturing of fiberglass shower stalls.  Because the stiff shell is created on a form in one piece, it must taper from the back to the front to allow it to be removed from the form.  Therefore, the width at the back will be smaller than the width at the front.  To simplify the tolerance assessment, the 2010 Standards specify that the shower compartment be measured at the center points of opposing sides but the expectation is that the width at the back will not be significantly less than the width at the front.  Similarly, the surfaces of ceramic tiles that form the wall behind a grab bar will not be perfectly flat due the manufacturing processes that make them.  Therefore, the manufacturing tolerances and the construction tolerances must both be considered when measuring the clearances between a grab bar and a tile wall.