Mike Wye & Associates
Suppliers of Natural Building and Decorating Products
  • Phone us on 01409 281644
  • E-mail us by clicking on sales@mikewye.co.uk
  • Write to us at Buckland Filleigh Sawmills, Buckland Filleigh, Devon EX21 5RN, England

    • LECA / NHL Limecrete Floor

    Technical Information Sheet

    LECA is lightweight expanded clay aggregate which provides an insulated floor. This is fine for existing buildings but will not realistically conform to current building regulations for new build or conversion. If an insulatated floor is required for new build or conversions, then there is no breathable insulation that can be used without excessive excavation. Limecrete can be used with a modern insulation in these circumstances if desired for a non breathing floor.

    LECA can be laid as loosefill insulation under a floor slab, and then mixed with natural hydraulic lime (NHL) to make a limecrete slab.

    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

    • We can offer advice on the design of limecrete floors. As a major supplier of both LECA and NHL we also offer unbeatable prices.

    Guidelines

    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.

    Typical installation

  • levelled and compacted ground
  • breathable membrane
  • loose fill LECA 10 - 20mm size coated for reduced capillary action
  • breathable membrane
  • limecrete based on 3 parts LECA to 1 part NHL 5
  • lime screed based on NHL 5 and sand.

    • 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 will take much longer to cure than NHL 5 and this will be an important consideration in winter working.

    Typical Specification

    1. Layer of geotextile
    2. Loosefill. A 220mm layer of Optiroc LWA insulation loose fill easily achieves a 0.45 W/m²k thermal value 230mm of LECA is equivalent to 50mm of extruded polystyrene.

    Area of oversite (m²) Depth of Optiroc LWA insulation fill required (mm)
     Clay Sand or Gravel Homogeneous Rock
    0 - 50200210210
    50 - 100180200210
    100 - 150150190210

    3. Layer of geotextile
    4. Limecrete
    9 bags of LECA to 5 bags of NHL 5 is 3 to 1 ratio (1 x 25kg bag NHL volume is approx 30 - 35 litres 1 x bag LECA volume is 50 litres)

    Example for 3 / 1 mix: 81 bags LECA to 45 bags NHL 5 will lay a 27 m² floor at 150mm (4m³) We suggest a mix of 1 part 1 - 4mm, 1 part 4 - 10mm, 1part 10 - 20mm all uncoated, for the LECA, mixed with 1 part NHL 5 and around 5 litres of water. For some applications a galvanised reinforcing mesh will be required. If you use NHL 3.5 this has a lower density, a 25kg bag of NHL 3.5 is 35 - 40 litres. Its greater volume means that the above ratio would become 9 bags of LECA to 4 bags of NHL 3.5 to achieve a 3 to 1 ratio.

    5. Screed A typical screed of 2 / 1 sand & NHL 5 is between 20mm and 50 mm thick depending on application. Flags or breathable tiles can be placed on top.

    Bulk discounts As well as 50 litre bags, we also supply in 1.25 cubic metre bulk bags. These represent a significant saving on 50 litre bags but obviously require onsite handling.

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    Mike Wye & Associates
    www.mikewye.co.uk
    t: 01409-281644 f: 01409-281669
    e:     sales@mikewye.co.uk