The first reference to the Clemens' marble floor and its cost came from a May 30, 1875 letter from Edward Tuckerman Potter to Sam Clemens:

"I do not remember that anything was said about the price of the marble floor. I find such a floor as I would recommend would cost about nine hundred dollars---or two fifty per foot. I think it would be more economical in the end and will go immediately on with it unless I hear from you to the contrary (within a week, say)."

Restoration work on the entry hall marble floor began in February 2003 and was completed in May 2003. As an architecturally significant component of the house, we took a restoration approach to the floor: Repairing and cleaning what was there, unless not repairable, in which case we matched the old material in composition, design, and color. A treatment plan based on these principles ensured contractors would properly restore the floor.

To test the project, quality control panels were restored and reinstalled first, appearing exactly as we wanted the entire floor. We used this section as a baseline to compare all of the work as it progressed.

Mechanics repaired the marble tiles off site at their shop. Repairs included patching stone, filling voids in stone tiles and gluing cracked stone tiles.

To protect the material for the long-term, the team needed to identify the conditions of the tiles and underlying causes of the deterioration. Deflection of the floor (the downward bend of a floor due to the weight of the floor itself and the loading and unloading of visitors) was identified as a likely cause of some of the problems with the floor. The original setting bed of cement on which the tiles were fastened, installed during the Clemens' tenure, proved inefficient under the family's daily use and later could not withstand the more than 60,000 visitors per year that would walk through the house. A condition assessment by stone conservators identified deterioration, dirt, and damage for each piece of stone and specified how each should be repaired.

• An Unusual Sub-floor:



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Not surprisingly, this old floor threw us a curve. After the contractor removed the tiles and the old setting bed, the sub-floor we found did not consist of a more or less even and uniform layer of boards over joists creating a more or less even surface. Rather there were exposed joists with a course of bricks in between each. These bricks are supported by tongue and groove boards, which are in turn supported by rails or cleats. This sub-floor made for an uneven surface with varying depths for the substrate (i.e., setting bed); in some areas deep and others shallow.

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A contributing factor for the cracked and loose tiles is the deflection on the floor. One-half of the front hallway had too much deflection. To fix that, we installed a steel beam (which runs the length of the room), to support the floor joists.

• Stone and Design Type:
  

  o	A herringbone marble tile floor composed of white rectangular marble units accentuated by smaller red and green triangular marble tiles.
  o	The white marble tile is a very fine-grained milky white stone with little or no other clouds or inclusions of color. This stone appears to be similar in appearance to "Statuary White" marble quarried in Vermont.

There are two different types of marbles used for the triangular accent tiles. The reddish stone is similar to a "Rouge Royal" stone from Belgium. The dark green triangular stones are "Verde Antique," which can found in Vermont quarries.

Modern Installation Method: To compensate for the uneven brick sub-floor and varying depths for the substrate the contractors installed on top of the substrate a crack suppression material. This material will prevent movement of the substrate from being transmitted to the tile in the form of cracks. The new floor installation system, on which the restored marble tiles were fastened, was designed to accommodate the growing visitor traffic for years to come.