When artist Erin Johnson and film editor Charlotte Prager moved into a seaside house in 2021, they knew only a handful of facts about the two women who designed and built it in 1971. The two women - art collector Mary-Leigh Smart and artist Beverly Hallam - were exacting about their specifications for the house, and they lived there together for over forty years. In "To be Sound is to be Solid," the filmmakers venture to decipher the house's opaque queer history by studying its complicated and circuitous floor plan. "To be Sound is to be Solid" is a film of layered intimacies and vicarious encounters. By investigating indefinability, erasure, and transparency in queer archives and scientific research, the film builds connections between lesbian, architectural, and environmental histories.