Abstract A full-scale model, containing numerous moisture sensors, was constructed to simulate the infection of the vulnerable floor-wall junction in a historic building by the dry rot fungus, Serpula lacrymans, and subsequent treatment by a chemical-free method. During the infection of the materials, growth of S. lacrymans became luxuriant throughout. Subsequent opening of the plaster walling of the construction, followed by aeration via ambient humidity then by fan drying, caused all exposed growth to become shrivelled and inactivated. Conversely, growth of S. lacrymans into an enclosed lower chamber, below the level of the flooring, was stimulated by the treatments. This latter growth, which emerged mostly from the stone walling, responded rapidly to direct treatment by ambient humidity followed by fan drying; however the shrivelled mycelium vigorously recrudesced soon after the restoration of suitable environmental conditions. Removal of excess moisture from the system, or isolation of timber from damp masonry, prevented this recrudescence. The salient features of chemical-free treatment via air drying were therefore demonstrated in a controlled and representative manner.