Timothy Haynes and Kevin Roberts, the founding partners of interior design firm Haynes-Roberts, are about to put their Soho loft on the market for $6.45 million.

Their 2,900-square-foot, full-floor home at 15 Mercer St. is an ode to their design sensibility, which mixes antique finds with midcentury classics.

The duo is well-credentialed: Haynes is an architect who previously worked for Robert A.M. Stern Architects, while Roberts worked for the Aga Khan Award for Architecture in Geneva.

The unit — for which they paid $3.55 million and renovated for approximately $3 million — features a private elevator entry, a great room with 14-foot ceilings, a woodburning fireplace with a marble mantle, a chef’s kitchen and original cast iron columns.

The master bedroom boasts floor-to-ceiling built-in bookcases, steel and glass French doors along with an en-suite spa-like marble bath with radiant heated floors.

The listing broker is Douglas Elliman’s Madeline Hult Elghanayan.