Frequently asked questions about limecrete
What is limecrete?
Limecrete is a combination of natural hydraulic lime and lightweight aggregate or sand, 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 in our limecrete. This would negate the breathability. We do add fibres to strengthen the floor further.
What are the benefits to the building of using limecrete/Why choose limecrete?
Breathability: Limecrete’s unique property allows moisture to pass through, helping regulate building humidity levels. This is particularly important for older and historic buildings where moisture control is vital for structure preservation and decay prevention.
Flexibility: Limecrete is known for its flexibility, adapting to a building’s natural expansion and contraction, minimising the risk of cracking and structural damage over time.
Insulation: Insulated limecrete floors provide excellent thermal insulation properties, enhancing a building’s energy efficiency. This is especially valuable in flooring applications, improving comfort and reducing heating costs. In older buildings, up to 20% of heat loss is through the floor!
Environmentally friendly (to some degree!): The manufacturing of hydraulic lime emits greenhouse gases. However, unlike concrete, lime reabsorbs CO2 as it sets. As limecrete gains popularity, its green credentials continue to improve. The RFG insulation is made from recycled glass, and plans are underway to produce this in the UK. Like any insulation, the emissions saved through reduced heat loss offset the insulation’s embodied energy.
No need for a damp-proof membrane: Unlike hardcore, the RFG insulation layer regulates moisture without wicking it. The limecrete floor, which is vapour permeable, sits above this. In the event of flooding, limecrete is an ideal subfloor, allowing water to gradually seep away over time.
Limecrete is widely specified by architects to protect ancient buildings. We are fully insured to carry out work on listed properties.
What are the disadvantages of limecrete?
We are very open and honest about limecrete floors and are aware that they will not work for everyone or in every scenario. Limecrete floors should be used as a holistic approach to the building as a whole. We are very happy to talk to you via email or phone about whether they would work for your building.
Why choose us for your project?
Specialised Expertise: We specialise in one thing and one thing only – providing exceptional limecrete floors.
Years of limecrete flooring experience: With nearly 20 years of experience laying limecrete floors, you can trust our skill and knowledge to deliver outstanding results.
Comprehensive support: From your initial inquiry to the project’s successful completion and beyond, we’re here to assist you every step of the way. We are fully insured.
Knowledgeable and diligent team: Our team is not only knowledgeable but also hard working and genuinely helpful. We’re dedicated to making your project a success.
Projects of all sizes: Whether you’re working on a large country home, cottage, new build eco home, renovation project or a cathedral, we handle each with the utmost care and attention.
Nationwide Coverage: We proudly serve homeowners across Great Britain, ensuring our expertise is accessible wherever you are.
Proven track record: We have many repeat customers, including contractors, architects, and fellow homeowners, attesting to our reliability and quality of service.
Rave Reviews: Our numerous positive reviews speak volumes about the satisfaction of our clients.
How long does limecrete take to set/How long until you can walk on limecrete?
This depends on various factors such as the lime type and content, whether it contains fibres and the ambient temperature. It is possible to move over the floor using boards after a few days, no point loading. The slab will continue to strengthen over the following months. It is possible to lay a floor finish such a stone bedded in a lime based product after 21-28 days but you will need to wait much longer to install a floor such as engineered wood as the moisture content will need to be much lower (2-3%)for this type of floor to prevent it from warping.
Why don’t you use a damp proof membrane?
The Recycled Foam Glass insulation layer regulates moisture. The floor is designed to be vapour permeable allowing moisture to travel and preventing it from being forced to walls.
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.
How do we mix our Limecrete and ensure strength and consistency?
We have two volumetric batch mixing trucks, Ronnie and Sally! Ronnie can hold around 8.5-9m3 and Sally can hold around 7-7.5m3 of limecrete. They mix the correct ratios of lime, aggregate and water. These ingredients are then forced through an auger to combine them. When you mix in a conventional drum mixer these different ingredients tend to ball together.
Fibres are added to increase the strength of the limecrete.
Which area do we cover?
We are based in Norfolk, but cover the whole of mainland Britain!
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 throughout 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 CO2 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.
With regards to UFH do you find the slab-less design takes longer to heat given that the pipes are laid lower than laying above the slab, within a screed?
Although the depth of material above UFH may take longer to reach its required temperature. The greater Thermal Mass of the slab with ensure heat is retained.
What is the minimum depth of a limecrete floor/What depth should a limecrete floor be?
This can depend on what your architect has specified and in order to meet a specific U-Value. The minimum depth for the slab-less design that we would lay to, with UFH would be 150mm RFG and 100mm Limecrete screed.
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.
Can you polish a limecrete floor?
Limecrete doesn’t naturally lend itself to being polished as once cured it tends to have small , non-structural cracks where it settles. We would recommend that either original flooring was put back or that a breathable alternative floor finish is used.
Is there a maximum thickness for the glass aggregate?
The Recycled Foam Glass aggregate that we use needs to be compacted in layers if the depth is above 300mm. The greatest depth that we have insulated so far was 550mm compacted.
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, a skilled and competent 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 will you mix the limecrete?
- How long do you expect the work to take?
- Have you previously worked with limecrete?
- Do you have any previous customers who are able to recommend you?
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 sarah@limecrete.co.uk