A Floor that Breathes

Operation breathable floor began some months ago with the understanding that laying a concrete floor with modern damp proof barrier can only lead to disaster.

Far from protecting an old building, a concrete floor increases dampness.  Because of the interface between walls (with little or no foundation) and floors, water trapped beneath concrete is forced directly into the walls.  We need a lightweight, breathable alternative – one which allows water vapor to escape and also insulates.

Firstly we lay a breathable membrane on virgin ground. Remember that we have dug down to a depth of two feet below finished floor level. The membrane will stop silt from rising up.

 The membrane covers the base of the walls too – more or less up to floor level.

We place a couple of drain pipes on the wet side of the room which shall lead water away outside down the sloped aspect of the site.

Where would we be without Brian – our trusty quarry man – to ferry our building materials  across hill and dale, not to mention down the terrible awkward lane way?

Clean limestone of about 4 inches in size forms a hardcore layer.  Strong and free draining the cleanliness of the stone ensures no moisture will be drawn upwards.

Our cottage floor (40 square m) takes about 18 tonnes – the layer is 8 cm deep.

Then we place another layer of membrane on top of the hardcore.

Our insulating material has traveled a long road up to Donegal – but the last mile is the trickiest of all.

A bulky cargo of LECA (Lightweight Expanded Clay Aggregate) – there are various kinds but this type is coated, which gives water-repelling and non-capillary properties. The air trapped within the fired clay balls gives it thermal insulating properties.

This layer is 10 cm deep and acts as a moisture break as well as insulating the floor. 

To stop it from rolling away out the door we butter a board with Lime to create a barrier.

Kieran has made measuring sticks which hang from the wall plate – he uses these to check the consistency of each layer at all points.

Old mortar boards serve to spread weight while walking across the leveled surface.

To date our project has used German, French and now Portuguese Lime – all slightly different hues of whitish gray – ‘Fifty Shades of Lime’ – anyone?

A pour-able ‘slurry’ is mixed to a ratio of 2:1 (sand:lime NHL5)

No wheel barrows on the LECA please – simply pass the bucket

It spreads beautifully (smooth as boxty) to form a screed, soaking into and bonding with the baubles.

The slurry layer is about a centimeter deep.

After this layer dries we shall need to add a stronger layer of limecrete – and replace our flagstones.

Almost time to brew a celebratory pot of tea!

36 thoughts on “A Floor that Breathes

  1. Hello!!! This is so inspiring – we have planned to do almost exactly the same process for all our floors. Great to see it in action.
    Also – we wanted to say thanks for one of our lime-rendering workshoppers, Glenda, who came to our workshop yesterday – because Alan told her about us (OzEarth), because of our contact on LimeWindow! It’s a small world. I love to see Donegal too: as a Co.Down lass, it makes me feel so, so at home! The Huon Valley in Tassie is very like, in its delightful damp, bumpy breastiness and roiling clouds, Ireland.
    So – long live lime! Can’t wait to see the next layer!

  2. Fair play Chloe!!
    Yes it is a wee world indeed! Your lime workshops at OzEarth sounds great – I hope you write a blog on how it goes. As does the Huon Valley look like a lovely place to live! Not so far from County Down in essence!
    The fellas and I have been so happy to lay this floor – after months of scrambling and at times crawling up the learning curve – (the various versions etc) – then only last week we got everything into place – execution was easy!
    The huge flagstone jigsaw to come – er – maybe not so much. 🙂

  3. That is going to be one cozy floor, how clever you all are! I wish I had had you make the floor for my shed/art studio, I did use a permeable membrane under gravel with slabs on top but it still has a damp spot on one edge, but this is only a temporary building. Next time I’ll know what to do!

    1. Andrea – if your studio building is stone, or old brick and lime mortar etc – the breathable floor system is the most compatible, and much less likely to be damp. It’s fairly ‘innovative’ here, with the first in Ireland being laid about 6 years ago I believe. The south of England seems to be much better clued into conservation and therefore breathable floors are more common. The proof of effectiveness shall be in the living!

  4. Absolutely love your informative blog, the pictures really explain in utter simplicity how everything fits and works together.
    I would be interested in learning more about your techniques and skills or the problems one might expect to face in such a project.

  5. Hi there, i have been fascinated by the floor you have constructed here, and i am now trying to source similar materials, the lime stone 75mm has been sourced easy, i am now struggling with the light weight expanded clay, i am guessing that it must be available in builders ton bags ? also is there a trade name for it ? i have found a trade name leca struggling to find a supplier in lancashire area, local builders merchants (travis perkins) recommended vermiculite balls, im thinking vermiculite is absorbant of moisture ? what make is the membrane, i am curious to ask, has it been succesful? is the flag floor dry and warm, sorry to be going on ! in one of the pictures i can see what i think is a black flexi pipe poking out of the floor, what is this for ? i work for a company that sells and moves bulk aggregates and my boss is adamant i need visqueen and concrete pouring over the top, when i explain that this will force water into my random stone walls and make it worse he thinks i have lost my marbles, lol, any advice will be glady recieved
    kind regards

    1. Paul you are not crazy. The breathable floor is not a perfect system but it is the closest fit you can get, for an old stone building. You are absolutely correct, a damproof membrane and cement shall certainly force rising damp directly into your walls – don’t do it!
      Our floor has been a great success – indeed it is dry as a bone even through long spells of heavy rain – no rising damp whatsoever.
      LECA is the brand name or original manufacture of this baked clay insulation (there are other slightly cheaper brands but I was advised that Leca is of proper quality) – but importantly, there are differing grades of Leca also. For this floor it is very important to use the COATED kind which is NOT absorbent. It is a fairly specialist product and not the cheapest, but the alternative is to use hemp, and this is only suitable to dryer climates. Yes it can be bought in bags that are two squared meters.
      The other vital point is to dig out the existing floor at a 45% angle from your walls, (not straight down, as you might do for a conventional building) – as generally there are no foundations & you risk destabilizing the wall.
      The pipe is just to carry away any ground water that might gather – an extra measure. You might want to include a radon pump (we didn’t).
      Over the next days I shall email you with further information on the floor. Good luck with the job!

      1. Hi, I’m in a similar boat to Paul and I can’t seem to find many suppliers of leca around the place. I’m in Kerry so that may be part of it. Could you please give me the same information you gave Paul so that I have a good start in my search? Thank you.

        1. Hi, love this post. We are in the middle of digging our floors up at the moment. A long process! Any advice on suppliers would be great. We are based in Waterford near Tipp border and are also having issues with people insisting we use concrete….
          My email is crazy_hoss@hotmail.com

          1. Hi Emily
            We got our LECA (and NHL) from Stoneware Studios in Youghal
            Very helpful indeed, Mark Dorian there gave me great time & advice – helped work out quantities etc
            Our cottage floor area is 40 square meters, so for a 10cm deep layer of LECA, we needed 4 x 2m cubic bags.
            In terms of the quantity of lime (NHL5 in this case) for the slurry and limecrete, we estimated 30 bags for a 70mm layer.
            Hope this gives a rough idea. Shall send out the specs for the floor.
            Good luck with it.

            1. Brilliant thank you so much, this is where we have got our NHL for the repointing upstairs.

              We keep being advised to use the damp proof membrane and concrete as people think that the floors will draw it in from outside through the wall.

              We are still digging at the moment, the doors are not wide enough to get a little machine in so it us all hy hand and kango hammer, underneath a few inches of soil it’s all lime shale mixed with a bit of clay and it is very hard going!

            2. Brilliant thank you so much, this is where we have got our NHL for the repointing upstairs.

              We keep being advised to use the damp proof membrane and concrete as people think that the floors will draw it in from outside through the wall.

              We are still digging at the moment, the doors are not wide enough to get a little machine in so it us all hy hand and kango hammer, underneath a few inches of soil it’s all lime shale mixed with a bit of clay and it is very hard going!

  6. I look forwards to reading more and seeing more about the floor, my floor is damp, made worse by the wet weather, also the guttering at the rear of the house needs replacing, and the front window needs mastic around the frame, and the cobbles outside have been laid by the previous owner, bringing the outside ground almost level with my internal floor, many jobs to address, many achievable jobs though 😉 looking forwards to sharing my progress with you

    1. Hello there – many many jobs indeed & certainly achievable. I got our 1960s steel guttering for silly money from an add in a local paper, then cleaned & painted it. What is your floor made from? We installed our inside floor a good 15cms above the outside ground level. If you don’t mind losing inside height you could raise it up but likely you need drainage around the parameter walls as shown here https://limewindow.wordpress.com/2013/03/08/french-drains/ .

  7. This project has become my ‘bible’ and reference manual for my own up- coming renovation , have the same problems to overcome and a few extra complications like having all the exterior walls covered in cement render and inside mostly in dry lining, rising damp ,dripping damp, and walls made of mostly mud with stone,.Excellent work done ,an inspiration for me ,thanks for posting it up its one of very few articles that have any relevance to me ,being based here in Ireland as well.

    1. Tony We are looking at doing the same as you – renovation of the old farmhouse (1850) which has dry lining, pebbledash put on in the 1950,srising damp, walls made of stone in the centre and mud and rubble on the external walls. How is your project coming on? Like you the LImewindow blog was a great find. Difficulty we are having is finding an engineer that will look at supporting the walls while we take off the pebble dash.

  8. Hi there
    I know this blog is a few years old, and has being inactive in over 8 months, but I have found reading this very interesting and would like your advice.
    Myself and my wife have purchased on old stone 2 up-2 down cottage which has being modernised in the mid 20th century with you guessed it cement plaster and dry-lined with polythene on the inside of the walls to hide all that nasty damp. I must admit to being a bit of a novice to working with old building and how them work, despite working in the construction industry in the past 20 years!!
    It’s being a learning curve to say the least, but I have found your blob very helpful.
    We have stripped most the walls of the dry lining to let the walls dry out. The outside walls are a different story as the outside of the house has a protection order on it form Dept of Arts, Heritage & the Gealtacht.
    Part of the ground floor is wooded with little or nothing underneath, so a system such as the one you have proposed would suit. However on the other half of the floor they appear to have poured concrete (not sure the exact buildup here) could this be responsible for the walls in this half of the house to be damper? If so, is the only course of action to remove this floor and re-instate a breathable one?
    Also could you tell my what type of breathable membrane you used, is Myplex one suitable? Also I was looking into the possibility of using Hempcrete floor on top of the Hardcore layer, with the possibility of installing a underfloor heating system in the lime screed.
    You had earlier showed reservations for using hemp in this wet climate, but I have found the site to be very dry with no standing water and even the ground under the timber joist floor is relatively dry. Your comments on this would be most welcome.

    1. Hi there
      Apologies for the very tardy response – the year has been too busy hence far.
      I hope you are getting on well with your house. Reservations about using hemp for the Donegal cottage were based on the generally wetter climate on the west coast here; the fact the cottage at the foot of a bank and the clay is not free draining naturaly, but sticky. With underfloor heating & on a dryish site, hemp is certainly viable. At a guess – the most likely reason for more dampness in one part of the house would be the poured concrete – labourious to remove but worth it in the long run. Concrete is simply not compatable with stone/old brick work.
      You ask about geotextile brands – and I’m not sure which brand we used – only to say that I chose a good quality one, not the skinniest, cheapest – nonethless it was just ordinary ground cover/weed control fabric. Used a 200m roll which was 4m wide and overlapped it by a couple of feet where needed.
      We didn’t get a great summer for building work but keep us up to date with your progress!

  9. I am researching the various options for addressing damp options in a period victorian villa style semi basement property. I’ve just read your interesting and informative article above. Can you give me some rough costs of dealing with say a typical room 12 x 12 foot room.

    Do you know who supplies the LECCA I am based in Dun Laoghaire.

    1. Hi Michele
      LECA can be bought from the Traditional Lime Company in Carlow as well as from Stoneware Studios in Cork. It is pricey enough but please check it’s current cost with the above sources as it was some years since I placed this breathable floor. The seller will advise on the cubic meter needed – we used a depth of 10cm – which for our floor of 16×35 feet worked out at roughly 1,300 euro. LECA comes in bags of 2m square. Be careful to use the coated type. Our cottage floor is beautifully dry & I recommend this system as long as it is properly installed – as seen in the article – but I can send specs for exact depths of all the layers.
      Hope this helps.

  10. Great blog & photos. Usually UFH requires a well insulated floor (bottom & sides)..so should UFH be ruled out for stone built houses? If applicable, would the same products/procedure as described above be suitable & what would be the sequence of layers ? What would be a good alternative to solid fuel heating for such buildings ? Thank you.

  11. Hello Louise! We met at The Gathering of Stones a few years back. This is the yank, Michele Carini- worked on the Leinster wall with Nick and lads. I hope this finds you well! I have been dealing with an old stone byre on The Isle of Skye that has been remodeled and has several such water issues associated with a cement floor and old stone walls. Have you ever used this system in conjunction with radiant heat? Finding so much food for thought on your blog. Lovely job!

    1. Hello Michele! Thanks for stopping by. I believe the breathable floor is used easily with underfloor heating – and geothermal heating systems – but I have no personal experience here. What a great spot to find yourself on Skye. Keep in touch 🙂 Louise

  12. Hello,
    Thank you for the detailed information and photos. I am currently in the midst of a similar project in northern Spain, but have been forced to modify the standard limecrete process for various economic and practical reasons. I plan to pour the slab on a gravel fill, with the insulation (mineral wool) above; the final floor will be oak set on joists laid directly on the slab. I am a bit worried about moisture from condensation, and am considering a “breather” layer of textile that is vapour-permeable but waterproof (a bit like Gore-Tex) set between slab and insulation, which is where the condensation should theoretically form. I can’t find any information locally or online about the possible effects that such a membrane might have on the functionality of the floor as a whole, nor can I find any information about how others have installed a timber floor on a lime slab — without the excavation and LECA fill to block capillarity, which are impossible for me at this site. Any insight or information you could provide would be greatly appreciated.

    1. Eric – sorry I can’t help with this query as I have zero experience of the use of membrane in such floors. I suppose I would ask myself ‘to where shall this condensation moisture escape?’ If the membrane allows it to escape upwards via the limecrete slab, then you are theoretically hoping to reduce the amount of moisture escaping? Lots of factors at play. You don’t say how deep the ‘gravel fill’ is. Spain is a dry place. Here in Ireland – a wet place – nobody believed this cottage could be dry without use of membrane etc. But believe me it is very dry. Good luck. Louise

  13. Hi – we are hoping to put in a similar floor but with underfloor heating included – any advice?

  14. Thank you for sharing this beautiful project! And thanks for answering all the messages people left! You have been an inspiration to so many!!!!

  15. This is an amazing discovery for me. I’m starting a project in donegal restoring and old farm cottage also. Is there any chance you can tell me where I can get this aggregate. UK or ireland as I have transport option in both. Also know this is an old blog but how has your floor lasted etc. Any information would be gratefully appreciated.
    Many thanks

  16. Hi Louise, absolutely love your approach to sharing information about this project. It is understandable informative and on point! Well done.

    We are embarking upon a similar project and wonder if we could chat about the suppliers you used and options?

    We are struggling to find the leca here in North Wales! I am interested in the geo textile is that simply the same fabric used for under drives and landscaping such as sold by screwfix? Finally the limestone sub base, is that necessary or was it installed because of the additional drainage system you installed? We have dug out and are currently monitoring moisture levels to identify if we need to do similar. Would love to chat or message. Many thanks in advance. Jane

    1. Hi Jane
      Thanks for visiting the site and I’m glad the posts are of use. Its a bit surprising to hear that Leca is hard to get in Wales but ours was ordered from an outlet in southerly Ireland, a nine hour road trip away so you may find similar distances involved. To answer your question about geotextile, yes, it is the ordinary stuff used in gardens/landscaping, being woven which lets water away. The clean limestone sub layer is necessary and inexpensive so better to have it (esp in wet areas) and if you send me an email seapink66@gmail.com and I can forward the specs we used for the floor system if that helps.

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