Why choose limecrete instead of concrete?
Our original motivation in the mid 1990s was to develop a flooring system to replace the earth and broken flagstone floor in our Georgian kitchen. We already understood the importance of 'breathing' buildings and the role of lime in achieving this in old buildings and so we did not want to interrupt the way in which the building dealt with moisture by putting in a hard, dense, cold slab of concrete so we began to look at the alternatives...limecrete (a blend of hydraulic lime and aggregate) provided an ideal solution, we also wanted to install underfloor heating and so it was important to insulate the floor and provide a screed for the pipes to run through.
Over the years, we have slowly refined the flooring system and the materials we use. We particularly wanted to help others, like ourselves, minimise the impact of their building on the environment.
Concrete is the most common construction material used in the world and is second only to water as the most consumed substance in the world. Every year, almost one ton of concrete is produced for every human on the planet which is staggering!
Cement is of course the principal ingredient in concrete and producing one tonne of cement results in the emission of approximately one tonne of CO2, accounting for approximately 7% to 8% of CO2 globally. The cement industry has made significant progress in reducing CO2 emissions through improvements in process and efficiency, but further improvements are limited because CO2 production is inherent to the basic process of calcinating limestone.
Lime too is burnt, but at a lower temperature and re-absorbs some of the carbon dioxide given off during burning whilst it is curing in the wall/floor but importantly it allows the floor to be recycled at the end of its useful life! This also helps to address some of the concerns we have about the level of construction waste going to landfill, in the UK this is currently 70-80 million tonnes per year – completely unsustainable!
Why should I use the Ty-Mawr insulated limecrete floor?
Ty-Mawr has been designing and supplying floors since 1999. Several hundred floors have been supplied for everything from humble cottages to churches and cathedrals to commercial premises all over the UK, Jersey and France.
Our floor has this year received Local Authority Building Control Systems Type Approval which means that it can be specified and used in all 376 Local Authroity areas in the UK, this is conditional on Ty-Mawr both designing and supplying the floor (please note we cannot supply a certificate for floors that we did not supply even if we did the original design as we would not have the knowledge of the exact components or mixes used or depths of layers laid).
Our uniquely experienced team are renowned for their excellent backup and support to ensure that you have peace of mind from the design and specification stage through to the final installation of the floor. They are well rehearsed in dealing with all parties involved including specifiers, contractors, clients as well as building control to ensure the floor performs as you would expect for years to come.
How does it meet building regulations?
The floor has LABC system type approval to meet Parts A, C and L of the current building regulations but this is only applicable to every floor being specifically designed and supplied by Ty-Mawr.
Do I need a damp proof membrane?
It is now recognised that polythene membranes, when installed into existing buildings, have the potential for forcing any moisture which collects beneath the membrane sideways until it reaches the existing masonry where it will be able to rise within the wall structure. This situation is often exacerbated by use of waterproof cementitious renders on the walls which trap the moisture within the masonry.
Our flooring system does not include a moisture impermeable barrier (Damp Proof Membrane). The control of moisture is achieved by using a layer of large recycled foamed glass aggregate or lightweight clay aggregate as a hardcore beneath the slab material both of which are certified to resist the wicking of moisture above a known height.
The limecrete slab is also vapour permeable material – in this respect it has the ability to both absorb and release water vapour. These properties provide regulation of damp within the floor system and maintain a surface which is dry and warm to the touch.
What about heat/thermal loss?
The insulating layer has excellent thermal resistance capability. We calculate the thickness of this layer to provide a specified U Value, taking into account the length/thickness of perimeter walls, overall floor area etc. In order to do this you need to complete a calculation form.
The slab is also made from an aggregate which itself provides thermal resistance. This figure is included in the U Value calculation used to determine the insulation layer thickness.
How thick are the layers in the floor?
Since both the loosefill layer and the slab have insulting properties, their thicknesses are dependant upon certain variables required to calculate U values. Completion of the calculation form will allow us to work out the depths required for your specific building. Although this may not seem important, it obviously has an impact on the warmth and comfort of the room and the long term energy consumption/running costs.
Can I lay the floor myself?
Full installation instructions are provided but we would advise that you use a contractor who has laid a floor before (limecrete or conventional concrete) as it is important to get the system, mix ratios, timing and measurements absolutely right otherwise problems may arise with volumes of materials required or the floor set can be compromised. If the contractor has only laid cement floors before then, as with all lime products, special attention needs to be given to protecting the floor to allow carbonation to take place. Free telephone support is provided and site visits can be arranged if required (usually expenses need to be covered).
How do I mix the limecrete?
Full installation instructions are provided with the floor but briefly, it can be mixed in a conventional cement mixer, pan/forced action or site mixer for larger floors. Please contact us for details if you wish to hire any of these mixers.
For larger projects, an automated VBT mixer is available, please contact us for details of specialist contractors experienced at mixing and laying our floors.
Can I pump limecrete?
It is not adviseable to pump the limecrete as in order to do this you would have to make the mix too wet, and this would cause shrinkage…also the water content of the Limecrete mix has a major effect on final strength. It should never be mixed so weak that it will flow. An ideal mix will be dry enough for the material to stand without being so dry that it appears crumbly. It should be homogenous.
We would suggest that it should be mixed and conveyed using a VBT mixer for large quantites, please email us for further information - tymawr@lime.org.uk
Can I build internal walls on top of my limecrete floor?
It is fine to build stud walls or lightweight block work on top of your floor. For any load bearing walls we suggest that these are built first on separate footings and the floor laid around them unless you know what compressive strength you are looking for, we would then be able to advise on the capabilities of the limecrete floor to meet those requirements.
How long does it take to cure?
The choice of hydraulic lime is the main factor here. We have a range of hydraulic limes to suit individually requirements and principles including British produced hydraulic lime which has a pozzolan added to it during the manufacturing process. This pozzolan has the effect of reducing the initial setting time and increasing the eventual compressive strength. Where work schedule constraints require a faster set, we can produce the floor with the NHL5 lime from France which has faster setting times and a greater compressive strength.
Hydraulic limes set by a combination of an initial chemical reaction (hydraulic set) followed by a slower carbonation process (absorption of CO2). Factors such a temperature and humidity will affect both of these processes. In ideal conditions, the slab will harden sufficiently to allow further works to be carried out within 3 days.
Screed layers, flagstones or other finish materials should not be laid until the slab material has fully dried – this can take up to 28 days depending on conditions.
We do not recommend use of de humidifiers or heating to accelerate this process.
It is important to schedule work as much as possible around the curing times of the floor but we know that in reality measures are taken to enable work to continue e.g. the following day using boards to distribute weight etc but if this is done, they do need to be removed when not being used for the curing to take place or the job should be planned to be able to give e.g. different sections enough time without impeding progress.
This is the biggest reason for people choosing not to use limecrete floors which is an enormous shame as the long term breathability of the building can be compromised for the sake of a few days, we are so concerned about the number of floors not going ahead for this reason that we will do everything we can to help you plan the job to ensure that it can be used.
Dealing with Ground Water?
It must be appreciated that the floor system is not designed to overcome ground water problems. Any likelihood of flooding of the sub base by rising ground water must be completely resolved before attempting to install the floor system. This is of course also the case for conventional concrete/DPM slabs.
We would suggest that a drainage engineer should be consulted, who will be able to identify any local information which would indicate the expected height of the water table during prolonged periods of rain or following heavy snow. Once you are satisfied that the ground water issue has been resolved, the floor can be installed and will function as designed to a given level of insulation and with the capacity to resist water ingress.
Can I install Underfloor Heating?
If under floor heating is to be included in the floor system, then a further layer of material is specified – this is a screed layer which provides a thermal store for the heat distributed through the pipe work.
Heat loss though the floor is controlled by the insulation layers beneath (as detailed above). No other insulation material is required beneath the screed but it is advised that you consult your heating engineer with regard to suitable edge insulation where the screed meets any external un insulated masonry.
Our screed is made from recycled glass aggregate with a hydraulic lime binder.
Should I use an electric or wet underfloor heating system?
We are not underfloor heating specialists and so will not advise on exactly which system to choose however the floor can be used with an electric or wet system.
Some underfloor heating suppliers are still nervous of insulated limecrete floors and make great claims against using them. We are happy to help you try to address any objections that you may receive from your chosen company or there are plenty of companies that now have experience of working with these floors including:
Abergavenny Heating - http://www.abergavennyheating.co.uk/alternative-heating.html
Jupiter Heating - http://www.jupiterunderfloorheating.com/
P.S. Having lived with an underfloor heated limecrete floor - there is no nicer way to heat or live in a room, the heat is right where you need giving a comfortable living space.
Which insulating layer should I use?
The HASPOR recycled foamed glass is favoured by contractors as it is easier to install, walk on etc (being angular as opposed to round like the LECA so it locks together), it also has superior engineering properties. We like the fact that it is made from a recycled product as opposed to the extraction of a virgin aggregate (which is what the lightweight expanded clay aggregate is).
We only ship full containers of the products to minimise road miles.
Should I be concerned about arsenic in the Recycled Foamed Glass?
No, it is in a smaller proportion than that you find in the earth!
Finishing Limecrete Floors
Can I use quarry tiles?
There are considerations with regard to using quarry tiles as a floor finish on to a limecrete floor system:
a. If a thin tile adhesive is used then an additional Glaster Screed layer may be required to give a flat level surface with minimal deviation.
b. Modern tile adhesives may well be vapour impermeable and so reduce the breathability of the floor system. All components of the limecrete floor system are ‘vapour open’ – i.e. they allow moisture vapour to move through the material. If a floor covering is added which is not vapour open this will greatly reduce the floors ability to function in this way. Impervious tiles may still allow some moisture vapour absorption/evaporation through the joints if a lime mortar is used to bed the tiles.
c. If the tiles are thin ( <10 mm ) and small, (< 300mm2 ) then bedding onto a lime mortar may not provide a sufficiently strong bond to avoid the tiles moving or lifting. Although lime is a very ‘sticky’ binder the tiles may be too insubstantial to remain in place.
You should consult the tile manufacturer for their recommendations regarding recommended adhesives and/or suitability of lime mortars as an adhesive or call us to discuss.
Can I use timber flooring as a finish?
Yes, you will of course need to have air gap. Care if underfloor heating is used as wood will move, you should put in position loose and leave unfixed to give it time to 'settle-in' before fixing.
Can I use stone or slate flags to finish the floor?
Yes - our limecrete floor system was originally designed as a floor slab for installation below a finished surface made from flagstones, slate tiles etc. The main point is that whatever you use, it should maintain the breathability so be careful not to then use an inappropriate bedding mortar, we would usually bed using a rich lime mortar, or a non-breathable sealer!
Can I just put carpet down?
Yes - the addition of a Glaster screed enables floor coverings such as carpet to be used - again make sure it is compatible and allows the floor to continue to breathe e.g. synthetic backings should be avoided.
We are currently researching various methods of achieving a polished or sealed screed finish to allow the floor to be left ‘uncovered’ as well.
Further information
Click here for further information and case studies.
maintains the 'breathability' of the building
Accredited Limecrete Floor Calculation Form
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