Lenhart Farmhouse, Historic farmhouse in Root Township, United States.

Lenhart Farmhouse is a two-story masonry house in Root Township with a gable roof and thick brick walls constructed in common bond pattern. Inside, a central walnut staircase rises through three stories, and later additions include an enclosed porch conversion to kitchen space and a bedroom extension.

The house was built about 1848 as a primitive Federal I-house with Greek Revival details. It was listed on the National Register of Historic Places in 2002. Between 1925 and 1931 the east porch was enclosed as a kitchen and a bedroom addition was built on the northeast side.

The house is a Federal I-house with Greek Revival details, a form named for its one-room-deep, two-story layout. Inside, the front door is three-panel walnut with a three-pane transom above it, and the first-floor rooms keep their chair rails and ash floorboards of irregular 4-to-8-inch widths.

The 1.67-acre home site sits on a knoll above the St. Marys River bottomland, with the historic Piqua Road and County Road 100E nearby. The brick cellar is reached by an exterior cellar door in the west gable end. The 1925 porch enclosure and 1993 garage help orient the later additions.

The house retains one original six-over-six double-hung wood window in the east side of the masonry ell, one of six windows with rough-hewn wood lintels and sills; the other four are attic windows. The three-panel walnut front door has a three-pane transom for ventilation.