While studying the gunflint industry at Brandon in Suffolk, England, many
years ago, I noted that the walls of several old structures were faced with
spent cores discarded by the flintknappers of yore, making for a very
uniform and attractive pattern.  Other structures were faced with irregular
flint nodules unsuitable for knapping, with the cortex removed from the
protruding portion to provide a flat surface overall. Considering the tons
of waste cores and unusable flint nodules that accumulated in Brandon over
the years, it is only natural that they were used as building material.
Flint nodules seem to have been used quite extensively for building in the
chalk country of southeastern England.