The reasoning behind the decision to install the insecticide and fungicide impregnated pressure-treated lumber hinged on the fact that the modern 6 x 6 lumber would last much longer than period materials.  Additionally, if untreated lumber had been used termites would have almost certainly infected the sleepers.  These termites would have then potentially spread into the surviving, and irreplacable, Madison-era framing.  So while it would have been more authentic to use a period material for recreating the framing of the ca. 1797 cellar floor, in the long term it could have possibly resulted in the loss of original Madison-era material.  Finally, because the sleepers will never be visible, using a modern material in this instance does not negatively impact the visitors’ experience of the space.