Limecrete – the vapour permeable solid floor


labc_4890 Reg_RegDetails

Mike Wye Limecrete is an LABC registered system

LABC represents all local authority building control teams in England and Wales. Members work cooperatively with building owners, home owners, architects, plan drawers, developers, building contractors and other professionals to ensure buildings are safe, healthy and efficient to meet the standards set by the building regulations. 


We do the maths for free!

It can be complicated figuring out volumes and U-values. Just tell us what you need and we will work it out for you. We can calculate all the design information you need for your floor, thicknesses, insulation values etc using our accredited design programme. We can provide delivered quoted prices for all the components as well. And no, we don’t charge for the service. 


Limecrete is a modern interpretation of a traditional solid lime or gypsum floor that can still be seen in many historic or well preserved older homes. It has also been used to create limecrete buildings with limecrete shuttered walls. Limecrete, known as green cement in the USA in the United Kingdom is normally used to create an alternative to a concrete floor with or without a DPM (Damp proof membrane).

It is vital to have an alternative option for a traditionally built house as an impervious, non flexible cement floor may create problems with dampness being forced into the walls at ground level which can result in poor insulation, mould growth with associated health problems and even structural damage. Many conservation officers with responsibility for listed buildings would encourage the use of the limecrete option rather than the less flexible and non-vapour permeable concrete floor build-up required by Building Regulations.

Limeash floors were originally made with lime putty and lots of a pozzolanic additives to provide an hydraulic and hard set. Although very effective, this method needs a very long time to harden and carbonate. A Limecrete floor is made using a natural hydraulic lime (NHL) powder that sets much quicker and potentially harder than the limeash floor. A mixture of NHL5 and well graded aggregates can be used to create the limecrete slab but it is also possible to introduce breathable insulation using an insulating aggregate and even underfloor heating.

Insulated Limecrete floor

Mike Wye & Associates Ltd. offer an option for an insulated floor using an insulating clay aggregate. This can be incorporated into the slab rather than using sand and in its coated form it can be used as an effective loose lay material below the slab to help prevent capillary action pulling moisture from the ground.

Limecrete offers a number of advantages:

✔︎ Increased vapour permeability, which is important in older properties

✔︎ Hydraulic lime is more environmentally friendly compared to cement

✔︎ It can be designed to meet the insulation requirements of building regs

✔︎ Natural and environmentally friendly

Our friendly and knowledgeable staff offer advice on the design of limecrete floors and then can work out the material quantities for your project. We provide a full service from design through to despatching the materials to any location. We do not charge for the calculation service.

Mike Wye & Associates provide a free guidance and quotation service for materials that can be supplied anywhere in the UK. We also offer a fitting service in the South West by our experienced team of conservators.

It is important to match the design of the limecrete to the needs of the building. Factors include the type of construction for both floor and walls, floor area and groundwater levels.

The thickness of each component depends on a number of factors on which we can advise. Some installers use NHL 3.5 which is moderately hydraulic compared to NHL 5 which is termed eminently hydraulic. NHL 3.5 based limecrete may take much longer to cure than NHL 5 and this will be an important consideration in winter working.

Example Specification

Limecrete Buildup

Limecrete 3D view


Limecrete section

  1. Levelled and compacted ground.
  2. Layer of geotextile membrane.
  3. Loosefill. 100mm – 500mm layer of loose fill 10-20mm coated clay insulation.
  4. Layer of geotextile membrane..
  5. Limecrete slab 3 parts clay aggregate 1 part NHL5 by volume at 100mm to 150mm.
  6. Optional 75mm screed of 2 parts aggregate 1 part NHL5 to bed heating pipes.
  7. Bedding screed 20-50mm of 2 parts aggregate to 1 part NHL5 to bed choice of breathable flagstone, tile etc..
  8. Grout with 2 parts aggregate to 1 part NHL of choice for colour


NB. 11-13 x 25kg bags NHL5 to 1m3 clay aggregate will cover 100m2 at 10mm depth


Limecrete Method Statement

LABC Limecrete Certificate

LABC Limecrete System Fact Sheet


Lightweight insulating clay aggregate

The expanded clay aggregate consists of lightweight, porous, ceramic granules formed by expanding special clays at high temperatures. The coated version of the aggregate is free-draining and has negative capillary action, good load-bearing properties and good thermal qualities (k = 0.10 w/mk), and is used as an insulating layer below the limecrete slab. This is a vital part of the build-up of a limecrete floor, offering an effective vapour permeable barrier to excessive moisture levels. See the graph image below of the test results. This shows that a minimum of 120mm is required for an effective capillary barrier.

limecrete graph

Water suction height above water surface and moisture content in kg/kg for the individual layers


The uncoated aggregate is mixed with NHL to form a limecrete slab – we recommend Secil NHL5 for this slab.


Weight varies due to the variation in moisture content.

50 litre bag Bulk bag
Price Weight 1.2 m3 Weight 2 m3* Weight
0-20 mm
£6.05 22 kg £81.79
570 kg
750-950 kg
2-8 mm
£6.21 22 kg £82.17
500 kg
700-900 kg
10-20 mm
£6.65 22 kg £91.87
500 kg
1,000 kg
10-20 mm
£6.65 22 kg £94.01
500 kg
1,000 kg

All prices exclude carriage and VAT.

* Please note: 2m3 bulk bags are unstable due to their height, and can only be supplied on dedicated transport to delivery locations with offload facilities. Please ask us for details

Geotextile Membrane

This vapour permeable, geotextile membrane can be used for gardening or landscaping purposes. We supply it for use in a build up for a limecrete floor. It comes in a 4.5m roll so we cut it down into linear metre lengths as required for ease of carriage.

Price per linear metre
4.5 m

All prices exclude carriage and VAT.

Secil Natural Hydraulic Lime – for prices please click here

Secil NHLs have been available since 1891 and have made a huge contribution to the construction market in Portugal. Secil and Mike Wye & Associates have joined forces to provide Portuguese natural hydraulic limes to the UK.

We believe these will offer an excellent and cost effective option for those wanting to use powdered hydraulic limes in their work, particularly for the ever growing limecrete market where NHL5 is widely used. Secil NHL5 is fast setting and ideal for limecrete floors whether used with sand aggregates or insulating aggregate such as ‘light expanded clay aggregate’. The Secil NHL has a similar strength to the French NHLs.


They are supplied in 25 kg moisture resistant bags and due to our bulk purchasing power we can offer unbeatable prices.

(individual bag)
(full pallet)
25 kg
NHL 3.5
25 kg
25 kg

All prices exclude carriage and VAT.

NHL Documentation:

NHL brochure (PDF format)
Product sheet (PDF format)
Health and Safety Sheet (PDF format)
Technical sheet

NHL5 is normally used for flooring such as limecrete floors or for highly exposed situations such as chimney flaunching etc.

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