Read your paper on tolerances. and am disappointed to find much tighter tolerances in Ballast’s report commissioned by the Access Board. Can you point me in the direction of further info on the subject? Specifically tolerances for pavement. Also any idea why the ballast report talks about access aisles and loading zones, but not the parking spaces? Or why it would have different tolerances for “running” and “cross” slopes in pavement? That doesn’t seem practical in a parking area, unless it was adjacent to a curb.

— Pete D.

ANSWER: As an architect I find Ballast’s report to be totally unrealistic.  He definitely is not the industry standard.

For further info here is actually ONE court case with stated allowable tolerances: Kirola V The City and County of San Francisco.

I cannot specifically comment on the ‘why’s and ‘wherefore’s of the Ballast report, but again, based upon my experience and professional opinion, his ideas of tolerances are not justifiable on a consistent basis.  The industry, architects doing construction observation and acceptance of work, allow for greater tolerances than Ballast.  This to me would equate to what the industry accepts.  Most of Ballast’s work on flat work appears to me to be geared toward road work with heavy machinery in large spaces which allows for tighter construction.  It is also usually constructed with a much more skilled set of labor than work performed on private sites.

I think you keyed into one of the most glaring issues with Ballast’s work.  He does indeed have a different tolerance for cross slope and running slope.  Since it is the same process of construction the tolerances should be the same in my professional opinion.  This to me represents a desired outcome not what can be actually accomplished in the field.  I have no idea if that is true, but what my thought on the subject is.

I hope this helps!

– Brad