Design - Do I need a damp proof membrane?

It is now widely recognised that polythene membranes, when installed into existing buildings, have the potential for forcing any moisture which collects beneath the membrane sideways until it reaches the existing masonry where it will be able to rise within the wall structure. This situation is often exacerbated by the use of waterproof cementitious renders on the walls which trap the moisture within the masonry. In flood prone areas DPMs can cause further issues retaining moisture after a flood pushing water into the walls resulting in the floor being dug up.

Our flooring systems do not include a moisture impermeable barrier (Damp Proof Membrane). The control of moisture is achieved by using a layer of GLAPOR recycled foamed glass aggregate as a hardcore beneath the slab material both of which are certified to resist the wicking of moisture above a known height. Control of ground moisture is controlled with external and internal land drains where required.   

The limecrete slab materials are also vapour permeable – in this respect, they have the ability to both absorb and release water vapour. These properties provide regulation of moisture vapour within the floor system and maintain a surface which is dry and warm to the touch.  The thickness of the slab (100mm) means that moisture vapour will not be transferred straight through the slab, but rather it is buffered in the lower half of the slab and the top of the slab should always stay dry.