Why is the layout of Notre Dame out
of square?

I tend to think it was cumulative error, perhaps
exacerbated by building around older buildings that had not been fully
demolished when the foundations were set out. That would have made the
traditional methods of sight lines, tight string and pythagoras, difficult to

A second problem for us was inadequate and inconsistent
source data. There are hand drawn plans and a very low resolution horizontal
slice through Andrew Tallon’s point cloud. We tried to get higher resolution
point cloud data but it’s a high profile government project, so a bunch of BIM
enthusiasts didn’t carry much clout.

Revit despises small angular deviations. In any case it
makes dimensions difficult and you face the prospect of custom making the
arches and vaults for every single bay.

The compromise we made was to make almost everything
orthogonal with repetitive bay sizes, but to make the north aisles of the nave
wide than the south, and the…

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