In 1870, Allston's executors sold it to the Sisters of Our Lady of Mercy,[8] who used it as a boarding school until 1905, when the Mullally and Pelzer families converted it back to private use.

[10] Following an intense backlash from the preservation community, donors, and others, the board of directors of Historic Charleston Foundation reversed course and voted to retain the museum house in January 2024.

Sited on a large lot in downtown Charleston, the house is rectangular in plan, three stories tall, and faced in gray Carolina brick.

A bracketed cornice and paneled balustrade separate the walls from the low hip roof, concealing it from view to better express the pure geometrical shapes of the house.

The windows of the second, most important story, the "bel etage", are the tallest; all 11 are capped with marble voussoirs and set into niches with red brick arches.

The whole ensemble is connected by a continuous stone string course, creating a kind of architectural necklace running around the house's east and south sides.

On the floor above, an elegant iron balcony with bowed, elliptical projections bearing the monogram "NR" spans the facade's full three-bay width.

In their interior design, neoclassical architects and craftsmen often created rooms in a variety of geometrical shapes (square, circular, ovoid, elliptical), embellished with elaborate plaster decoration and striking polychrome.

[12] The large rectangular withdrawing room at the front of the house has soft gray walls and white wainscoting topped by a multilayered gilded cornice.

To the south of the house is the garden that was originally laid out in a geometric arrangement with patterned beds of flowers, ornamental shrubs, and large orange and grapefruit trees.