Having excavated the floor to the required depth, cork insulation boards are secured to the external walls and a geotextile membrane is laid on the floor and rises up the wall. In to which the Recycled Foam Glass (RFG) is poured over the surface to a minimum depth of 120mm. This is the insulating component of the system. Most buildings require a depth of around 150mm to comply with building regulations.
The RFG is then compacted to achieve a flat surface
An example finish of a limcrete floor
The floor is then covered again in the geotextile fabric which overlaps the first layer of fabric along all edges.
Its at this stage that any underfloor heating pipes can be fitted to a Geogrid (pictured above). Its important that the Geogrid is used for this element as it allows the floor to remain suitably porous and breathable, thus reducing the liklihood of damp.
Once the underfloor heating pipes have been installed the limecrete screed can be laid. This is laid approximately 100mm and floated.
We like to rub a sponge over the floor the following day to remove the surface 'fat' which encourages carbonation but also serves as a more 'open' surface for laying stone slabs on to.
Limecrete floors have been around for quite a few years now, but it is only in recent years that they have been approved by the Local Authority Building Control (LABC). This means that if you have a building that was built using lime mortar (this is predominantly solid wall construction, Cob buildings, but also some brick cavity Victorian buildings) then you should not be made to pour a concrete floor! Concrete floors and their accompanying Damp Proof Membranes cause an awful lot of problems in older buildings, as they simply push moisture away from the floor and into, and up, the surrounding walls, hence the rising damp myth.
With a limecrete floor, moisture is acknowledged and controlled through an incredibly simple system using very basic materials. Instead of trying to wrap the floor in Damp Proof Membranes, a breathable geotextile is laid. This is not a water barrier, but simply serves as a way of preventing any dust particles from clogging up the next layer, which is the insulating hardcore. This material is very much like pumice stone, it is incredibly light, highly insulative and highly porous, which means it wont wick moisture from the ground and into the finished floor and even if it does get wet for whatever reason, it will dry out at the first chance to do so.
The floor is finished with a simple screed mixture of a coarse aggregate, a strong NHL binder and reinforcing glass fibres.
It is worth noting that when having a limecrete floor, only a compatible finish should be installed on top of it. A standard flooring finish for our limecrete installations would be stone slabs such as limestone, sandstone, slate etc, but these must also be laid in lime based mortars. Carpets, timber flooring and vinyls are not compatible and are likely to cause moisture problems and/or decay.
Limecrete floors are compatible with any building, whether they are traditional in nature (such as solid stone walls, most listed buildings and churches etc) or modern (passivhaus system).