For this project we worked with an Architect applying Diathonite Acoustix, sound-deadening, breathable, non-flammable, insulation-efficient lime plaster.
lime
What happens if you use cement-based mortar
This is what happens when you use modern strong cement-based mortars over soft 400-year-old brick and lime mortar. Trapped moisture has destroyed both bricks and mortar. Lime is the only way forward if you don’t want to harm your buildings.