Limecrete

[Andrew Bodenham]

Who has had experience of mixing & using limecrete?

I need to cast a layer over the ground beneath a suspended floor, to stop bad smells rising due to contaminated groundwater. (Don't ask - it's a bad combination of dodgy cesspits, high groundwater and interesting geology)

Initially I thought of concreting, but I'm now thinking limecrete to try and be slightly greener. Does one use hydrate or hydraulic for limecrete. In this situation it will not be structural in any way - it's just got to sit there as a fairly impermeable layer.

 

[Gervase]

Use NHL5 hydraulic. However, it's 'impermeability' may be a moot point. Limecrete is supposed to be breathable, and that may mean that the methane, sulphides and mercaptans that make your soil so smelly can come up through the slab.

 

[biffvernon]

A sheet of the polythene of the grade used for radon prevention might be more effective.

 

[inwood]

The limecrete solutions supplied by the major lime suppliers require a capillary gap to work effectively. In essence the base layer (which is wrapped in terram or similar) provide both insulation and a capillary gap, stopping any water being wicked upwards into the limecrete.

If you're simply laying aggregate and NHL5 lime on a damp surface the lime will draw the moisture up and become damp itself. If you don't intend having a capillary gap then a vapour/damp barrier of the kind suggested by Biff will be required.

However this will have the downside of forcing any dampness to the edge of the walls where it will accumulate over time and be drawn upwards.

You could leave a small gap around the perimeter of the floor to allow dampness forced to the edge to evaporate (assuming you have reasonable air flow beneath the suspended floor).