Limecrete FAQ

Frequently asked questions

What is limecrete?
Limecrete is a combination of natural hydraulic lime and lightweight aggregate which can be used as an alternative to concrete. This creates a breathable floor slab with a certain amount of flex.

We never include any cement or admixtures in our limecrete. This would negate the breathability.

What are the benefits to the building of using limecrete?
Limecrete is breathable. It behaves in a similar way to other natural building materials such as timber, straw and earth. Water vapour can escape through limecrete. If you have a waterproof floor and breathable walls water vapour would tend to travel up the walls, damaging them.

Limecrete is widely specified by architects to protect ancient buildings. We are fully insured to carry out work on listed properties.

How long does limecrete take to set?
This depends on various factors such as the lime type and content, whether it contains fibres and the temperature. It is possible to move over the floor using boards after a few days but we would not recommend this due to the possibility of weakening the slab. A slab strengthened with fibres is generally safe to walk on after a week but will continue to strengthen over the following months.

Why don’t you use a damp proof membrane?
The limecrete system we recommend was developed by Ty-Mawr Lime and has LABC (Local Authority Building Control) approval for use without a DPM. The RFG insulation layer regulates moisture.

If limecrete is laid onto a normal sub base i.e. compacted hardcore, water may be sucked into the slab by capillary action causing damp problems.

I saw it go wrong on TV – will this happen to me?
The near failure of this limecrete slab was the freezing weather conditions in which it was installed and the method of mixing.

We have successfully installed limecrete in the winter by heating the water used in the limecrete and heating the building in which it is installed. For outdoor applications we would advise you to avoid installation in the winter months.

Our mixer has been especially customised to mix limecrete.

How strong is limecrete?
Limecrete is strong enough under compression to be used as the floor slab in a home. It can be strengthened by increasing the lime content and by adding
fibres. This makes it suitable for applications such as a workshop floor. The lime content should not be increased excessively as this compromises breathability.

We use NHL5 (Natural Hydraulic Lime strength class 5).We cast test cubes on site and have them crushed independently. Our data therefore reflects our work and not laboratory conditions.

What is a volumetric mixer?
A volumetric mixer measures the correct ratios of lime, aggregate and water. These are then forced through an auger to combine them. When you try to mix limecrete in a conventional drum mixer the different ingredients tend to ball together. It is tempting to splash more water in to loosen the mix the way you can with cement, but this substantially weakens the limecrete.

In what way is limecrete environmentally friendly?
The process of manufacturing hydraulic lime releases green house gases. However, unlike concrete, lime reabsorbs COÄ as it sets. As published figures vary as to how much less polluting lime is than concrete we avoid  quoting them. As the market for this product increases, the green credentials will continue to improve as production of lime becomes more efficient.

The RFG insulation is produced from recycled glass. Currently, this is imported but again, as the market increases, it will become more viable to produce it in the UK. As with any insulation, the emissions saved by reduced heat loss pays back the embodied energy of the insulation.

Can I install underfloor heating?
Yes. Limecrete is totally compatible with underfloor heating. We will be happy to discuss the insulation value of the floor with your heating engineers.

What floor finish can I use?
Whatever you use must be breathable, stone, tile and wood can all be suitable. Please beware of non-breathable adhesives. Carpets made of natural fibres and backing with underlay such as hessian or felt are also suitable.

Do I need to use a specialist contractor to install limecrete?
With our experience we are able to offer detailed advice and efficient service, of which we are very proud. That said, any builder should be able to carry out the work as long as they understand the material. If you are in any doubt, it may help to ask contractors the following questions:

  • What is the make up of the limecrete?
  • How is the floor insulated and what U value will be achieved?
  • How will damp be controlled?
  • How will you mix the limecrete?
  • How long will the work take and how will you deal with joints?
  • Do you offer a guarantee?

What specification do you recommend for my job?
We will be happy to provide advice and a quotation. Please call us for free on 0808 168 5463 or email office [at] limecrete.co.uk

18 thoughts on “Limecrete FAQ

  1. Hello

    I am looking for a company that can install a limecrete floor in a domestic period property.

    Kind regards

    Roger Bastow

  2. Hi there. I am wondering whether what floor to put down in my strawbale kitchen, it already has an uneven limecrete slab.

    I know that it has to remain breathable, but it has been pointed out to me that natural stone slabs are not breathable anyway – the moisture transfer must be via the gaps – so am thinking that any type of flooring, even concrete, would work as long as reasonably wide grouting is left between the slabs . Is that correct?

    Another alternative would be to just use another limecrete layer screeded to match the existing floor level, then polish it up. Which would you advise?

    Thanks
    Steve

  3. I am also looking for a firm to give me a price to install limecrete in a grade 2 * manor house lower ground floor in cornwall.
    You can e mail or ring me on 07711310956
    Thanks
    Greg Schmid
    Director GTT Developments Ltd
    Building contractors

  4. Hello,

    I live near Frodsham, Cheshire.=, in an old farm house. I have recently had the kitchen increased in size with an oak framed/glass extension. The floor slab it sits on is concrete. It now requires 100 mm of insulation,onto which I was planning to get a concrete screed poured, which was to be polished after drying out.There will also be an electric underfloor heating mat. I would prefer to use limecretefor its breathability, but I fear that the costs would be prohibitive. The extension is 6m x 3m and the floor needs to be brought up to the height of the existing kitchen, which is currently 180 mm higher. The kitchen already has a concrete floor, and so I am unsure how to blend the two floors together.

    I would be grateful for your advise on laying a polished limecrete floor and and what the estimated cost would be. I can be contacted by email or on:

    Many thanks,

    Jane Stokes

    1. Dear Jane,

      Could you email me more detailed specifications for this project. I would need to know the address of the project. The thickness of the insulation ( we usually specify 150mm glapor foam glass) and the thickness of the screed (we usually suggest 150mm. The area of the floor and whether you want a price for both regular sublime limecrete and polished enhanced limecrete. Please email me at tom @ limecrete . co . uk

      Many thanks,

      Tom

  5. Hi,

    We have laid limcrete thoughout the ground floor of our house, with underfloor heating underneath. I understand that wood flooring is not advised in this situation due to the possibility of warping from the heat and potential moisture from the floor.
    Therefore, we have decided to install limestone flagstones. The builder feels we should pour some sort of screed over the top to ensure it is level?? I also need to find out what grout/bed it should be laid on. I have been told it should be lime based, so wondered if there is a recommended mix etc?

    Thanks

  6. Hi,
    I am interested in installing a limecrete floor, could I lay it on a DPM with large flagstones then bedded on top via a lime mix?

    Regards

    James

  7. hi,
    i am in the process of making a floor on soil. I want to put down a limecreet floor, but want to know if and what kind of a membrane to put down.
    I am buiding a house in portugal, where it can be cold, long heavy rain perodes and hot too. the floor will have a 200 mill hardcore layer, a 100 mill layer of leca and 100 mill limecreet.. The soil is damp and on a slope, does the mebrane therfor need to be breathable? and, where to put it ie underneath the leca ore around the hardcore? what make/ material?
    look forward to your advise,
    ewout

  8. Hello, we are hoping to install a limecrete floor in a building subject to flooding. Is this appropriate and are there any special measures that need to be taken when mixing/laying the floor? Are there any other considerations you think we should be aware of?
    Thanks

  9. Do you have the K value (thermal conductivity) for the limecrete floor so i can work our the floor resistance.

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