Limecrete is a relatively recent innovation in building terms but fulfils a long overdue need when installing solid floors in historic properties; breathability.
The conventional wisdom in the building industry over the past 50 years has been to install concrete floors over a dpc. If this was done correctly then it is likely the damp never came back but, as is so often the case, poor workmanship and/or poor specification can create a whole host of problems. We have come across several cases where the dpc was omitted or was not contiguous to the outside walls and where the underlying moisture had found its way to the edge of the slab and up the walls. The use of limecrete has effectively eradicated this problem as the entire surface area of the slab is able to breathe.
At the Organic Building Company we have developed our own techniques to good effect. Depending on the depth of the oversite and the desire for improved insulation, the composite will typically consist of at least 50mm of LECA, a breather membrane, 100-150mm Lime/LECA and then 60-75 mm of Lime screed followed by the final finish, set on a bed of lime mortar.
Depending on the depths of the various layers limecrete floors can be specified to conform to Part L (Insulation Standards) of the Building Regulations, which are applicable to new buildings but the same standard can also be adopted for historical properties, resulting in a warm floor.