Laboratory Verification of Water Vapour Permeability of Plaster Compositions

There are many significant historic buildings of our national heritage in the Czech Republic that worth protecting. These astonishing buildings are most frequently damaged by water, precisely speaking by moisture. The moisture can come from several sources, for example from a flood. That is the reason we should know about the materials and their behaviour from the point of view of the moisture in the vapour form as much as possible. This paper summarizes properties important for material water vapour permeability represented by water vapour resistance factor. There are stated and tested three compositions of materials, commonly used in the praxis, in the paper. The compositions are: basic adhesive diffusion mortar with no finishing; basic adhesive diffusion mortar + silica penetration; basic adhesive diffusion mortar + silica penetration + silicate plaster. Not only diffusion parameters but also the border condition and their impact on the material behaviour have been tested and determined. We should know how to treat these buildings during a flood well. After previous floods that damaged many valuable buildings it seems to be a very priceless familiarity. Moreover the tested values help to find out if there is going to be condensation of water vapour on the surface of the tested material inside a building.