Lime floor instead of concrete in a cob house?

Hi To everybody, Newbie here!!
I am renovating an old french farmhouse, made of cob and columbage.....i am happily re doing bits of damaged cob in the walls, but had a flash of questioning over the floor......we hadnt considered anything other than concrete, but having looked more and more into cob houses I cant imagine that this would be good for the house. My question is....can I use Lime and sand as a floor slab, and roughly what mix......also how thick to use it, plus, once its down how long before we can continue the build.....And another thing.....could I use glass bottles (broken or otherwise ) for insulating it? ......thanks to anyone who can help in advance!

You are referring to one of the oldest building materials, lime mortar. The Wikipedia article below is pretty informative:

http://en.wikipedia.org/wiki/Lime_mortar



The lime floor might be more "historically accurate" for your house, and might actually be better than concrete as it can "self heal" small cracks.


I personally have been experimenting lately with cement mixed with various other things (like plain red clay dirt from my yard) to make economical
building material. Concrete is normally cement mixed with sand / gravel (aggregate).


As for using bottles, broken or otherwise in your floor- probably not a good idea, and it would do nothing for insulating properties. (and not good for your feet)
Maybe use rigid insulation board under the lime floor. This would decouple the floor from the earth.

Thanks for that. Couldn't the glass act as a thermal heat store beneath the lime floor? And would a rigid insulation board stop breath ability? I have used bottles under my pizza oven embedded in a cob mix so just thought about moving up a size to a room.

Hi Katie,

Really busy at the moment, will check in later to see if you have more questions, but here are some links to read through that should keep you reading for a few days...

http://www.lime.org.uk/limecrete-floor/

http://www.lime.org/lime_basics/faq.asp

http://www.americanlimetechnology.com/

Thanks for those , I had read through them...... still unclear on guidelines for amounts or thickness etc. I am not seeing anything concrete ( no pun intended!!) I want to be armed and ready with facts before I propose using lime to my OH -who has been chatting to a builder...... Not used to cob builds.....

Hi Katie,

What is an OH ?

If your not doing the building the stick with then basics. The actual process, design, differing technologies-modalities are beyond the scope of many DIYers. I could spend several hours explaining different methods, and still be way outside the scope of your project. Don't let any builder that doesn't have at least 10 years of experience working in traditional or natural methods of building talk you out of something. I often get very strong opinions from GC and builders that don't know the difference between cob and lime render or how a timber frame even works. Inevitably they (the GC) want you to buy and use what they know and understand.

Regards,

jay

Thanks jAy , an OH is my other half ( husband) .
So are you saying stay clear of lime flooring if we are doing it? We are doing everything. We are probably a step on from the average diyer as we have already built log cabins and re roofed our house with traditional canal tiles, also laid concrete slabs and rebuilt a couple of the rooms in the house. However I am concerned that this room needs a breathable floor as its an old wine cave with earth floor. It will be our hallway and staircase.
I want to keep this building upright as long as we can.

Pictures, Katie, we need to see pictures. (My curiosity is only because at one time I was seriously looking at old farmhouses in the Aude departement.)

What do you have for a floor slab now? Is this an earth floor with a perimeter foundation of stones for the walls? Is the floor damp most of the time? Or dry and dusty? Can you drive a nail into it with a hammer, or do you need a drill with a masonry bit to penetrate it?

Omg! I will have to take pictures but I'm not promising I can attach them! Technology is not my bag!
Ok the floor is clay, dry and you can wack a nail into it with a hammer.... We are digging down about 2 feet as it needs to be lowered for the ceiling height, even 2 feet Down it is dry. We have 2 walls that look like they have foundations and 2 which will need reinforcing supports..... We are using sds drills to dig down or a pick axe.

Hi Katie,

Oh my know, please do use it, it is just beyond the skill sets of most DIYers so if you are doing it yourself then I can see why you are looking for details. I would need details (blue print elevations) and photos of you project to give more accurate advice than I have thus far. Advice in forums like this can be tricky, and as a professional I have to be careful that you do not take something I say out of context.

I am going to give you my contact at "Lime Works." Tell Tyler (Rodkey) I sent you. He will help or knows who can in your area. If you send me photo and blue prints I will post them here for you if that is giving you trouble.

http://www.limeworks.us/

Hi Katie,

Oh my I didn't mean for you not to use it, please do use it, it is just beyond the skill sets of most DIYers so if you are doing it yourself then I can see why you are looking for details. I would need details (blue print elevations) and photos of you project to give more accurate advice than I have thus far. Advice in forums like this can be tricky, and as a professional I have to be careful that you do not take something I say out of context.

I am going to give you my contact at "Lime Works." Tell Tyler (Rodkey) I sent you. He will help or knows who can in your area. If you send me photo and blue prints I will post them here for you if that is giving you trouble.

http://www.limeworks.us/

Thankyou, I Appreciate it. Tomorrow I will go do some measurements and take photos of the space. Great advice from everyone so thankyou

katie ashton wrote:Omg! I will have to take pictures but I'm not promising I can attach them! Technology is not my bag!
Ok the floor is clay, dry and you can wack a nail into it with a hammer.... We are digging down about 2 feet as it needs to be lowered for the ceiling height, even 2 feet Down it is dry. We have 2 walls that look like they have foundations and 2 which will need reinforcing supports..... We are using sds drills to dig down or a pick axe.

Sounds like a lime treatment could do what you want with the floor. In addition to the contact Jay gave, these folks are in Belgium and might be closer for you to work with.

Sorry Katie I thought you were here in North America some place, my mistake.

John how could you tell she was in Europe? You have to teach me these kinda things...

Brilliant! Thankyou guys.

Katie, if you do not mind sharing (understand if you don't) where are you located at?

Jay C. White Cloud wrote:Sorry Katie I thought you were here in North America some place, my mistake.

John how could you tell she was in Europe? You have to teach me these kinda things...

"French farmhouse" in the original post? That may not conjure up any images for you, but for me it makes me smile thinking of the road from Narbonne to Carcassonne.

Pourquis suis-je ici en Georgie? Je ne sais pas.

Gosh John, I new I was in a rush this morning, I didn't think I missed that much...You must be laughing at me...:

Now that I know where your at...(silly me) I can focus better.

Here is a photo link for ideas:

https://www.google.com/search?q=limecrete+floors+in+america&safe=off&es_sm=122&source=lnms&tbm=isch&sa=X&ei=cHxMUrbXM6qf7ga8sYDICA&ved=0CAkQ_AUoAQ&biw=1280&bih=685&dpr=1&qscrl=1


Now there are a number of less intrusive ways to do all of this. One is, (unless you have a moisture issue) is just live on the cob floor. The other is to dig down just a bit and mix lime with the cob as John (?) suggested. Another is to dig down to where you want the floor level to be, lay down sleepers, and lay a traditional slab floor of heavy plank 40mm to 80mm thick that are jointed and float on the sleepers. If you like the wood floor concept I can go into more detail. You have plenty of locals help for limecrete floors.

Regards,

jay

Sorry guys I went to bed and left you all worrying about where in the world I was! We live in the southwest of France, where there are millions of these cob farmhouses, but it seems apart from rendering in lime the floors all seem to be concrete. I definately Am more comfortable with a solid floor otherwise we have a community of furry friends living beneath the floor.... And I'm afraid that is not my thing. I will check out the links and get on with the photos. And thanks again to you all!! Didn't expect such a good response.

Here's a couple of photos...... I hope! The room is around 3 m x 5m and the house is built into a hill. So the room is behind our lounge and about 1.5m higher.

Magnifique!

Given that your soil is dry, the drainage is adequate and the lime you add could even be in the form of lime-water. Now that would really be making it a cave, where lime saturated water drips onto the floor and makes the ground one solid sheet of limestone. But that sort of thing takes time. Scratching lime into the floor and watering it in should give you a very serviceable floor, and the good thing is, if it comes out lacking the first time around, you can always give it a second treatment.

Ok guys, I have spent the day reading, phoning, emailing around about where I can get stuff from.....
Lime is not a problem, nhl 5 is made round here. However the clay balls, or pozzolan are expensive. Sooooo could I use the limestone 0-20mm as the base layer and use a limestone type aggregate in the mix? I will separate the layers with geotex. I think if this is acceptable it works out the most cost effective and comparable to cement floor.....price wise.

Hi Katie,

First, please put concrete out of your head, (and anyone else you know of that might consider it.) Portland cements (even trace amounts in a mix) contribute to moisture issues in vintage and earth (natural) based architecture. The always have a dank and musty smell and feeling to them. The best analogy I can offer is the difference between a wet cotton sweater and one made of fleece or wool. Portland based masonry acts like a "wet cotton sweater," and hold moisture (and mildew as well as other "nastiness" that gets into it) while a cob of lime masonry product act like a piece of fleece or wool. It might get wet but it will move that moisture out and away to evaporate, so even if wet you stay warm.

Now for you current idea, yes I believe it will function, but not that much differently than cob you already have..it just is not that much harder in that application. So think of it this way, if a stone floor is a 10, an oak plank floor a 7 to 8, then a cob floor is about a 3 to 4...in the way of hardness. If you add lime to it in the proportions you suggest you will probably only get a 4.5 or 5 where an actual "lime masonry" floor is a 7.5 to almost 10.

I know you said you did not like the idea of a wood floor, but your reason was "critters." Among my skill sets is (was) State Supervisor in Pest and Wildlife control. If you have a rodentia issue in a structure, (like under you floors) that has nothing to do with the floor or its type...that has to do with control and mitigation of the offending species. Most rodentia that will infest a home (rats, mice, etc) can dig and chew their way through almost anything including concrete, so do be fooled by what folks tell you (including most pest control companies) about these little guys. You have to confront them on an "ethological level." So in that case, I still would consider wood. The only time I suggest or recommend earthen or lime masonry floors is if I am using some type of hydronic heating system, and even then you can combine that with the slab wood floor. My next suggestion after wood is a free large stone slabs or tile bedded in a gravel base (many different ways of doing this.) Monolithic floors are on the bottom of the list mainly because of cost and labor involved in constructing and servicing them with the need arises.

So I guess, in closing for now, if you don't select a full solid lime masonry floor (like limecrete) you might as well stick with cob. Either way let us know how it goes and what you select. It will be interesting to follow along and see what you think? Thanks for the pictures and updates that was great, love to visit sometime.

Regards,

jay

Hi Jay, dont worry ......I am not going near a concrete floor....what I am trying to do is make a floor that will be solid and support our underfloor heating plus a flagstone or terracotta tile on top. What I dont want is concrete......for all the reasons you have mentioned. BUT I have to know my onions before I convince my husband and his adviser.....so, limecrete, is what I want to do. If I am honest I would have liked a polished earth floor....but my husband passed out at the suggestion! That will take some work I think. In the meantime, I need to have a solution that works for us and is cost effective....hence trying to use a limestone gravel.... Just waiting for the email responses from a couple of limecrete companies and then hopefully all will be well!
Thanks again and pop in if you are passing!

I am not going near a concrete floor

Happy to read that!

.....so, limecrete, is what I want to do.

Excellent....

but my husband passed out at the suggestion

Silly man...and you can tell him I said that, but then again maybe not if I ever want to come for a visit...

what I am trying to do is make a floor that will be solid and support our underfloor heating plus a flagstone or terracotta tile on top

Now I have something to work with...

If you are planning on "under floor hydronic heating system" you want a masonry floor, that we do agree on 100%. You can use it under wood as well and it works almost as good (sometimes better) but that is a system that is proprietary to my designs and would be outside the scope of most contractors you are going to get, so we need to run with what you are thinking about. So if I was your neighbor and helping here is a break down of steps (modifiable within certain parameters).

1. Dig down to prerequisite amount to have finished floor layer at the level you require for finished floor to ceiling height. Your contractor (or you) should render this as an elevation drawing on paper or CAD before work commences. ( Proper planning avoids crisis management.)

2. DO NOT undermine perimeter (interior or exterior) walls. There should be a slop of original material at the "angle of repose" for that materiel and/or 40 degrees. You can do 90 degrees down wall plane but special considerations and conditions apply (i.e. wall stabilization, shoring, etc)

3. Lay down a 100 mm "lift" (technical term for level) of 20 mm to 30 mm stone (crush and screen limestone would be great but any clean rock will do). Hand pack this, screed level, and repeat rendering a depth of 200 mm, this would benefit from mechanical vibration compactor or very long and strenuous hand packing (8 paces with a machine or about 20 poundings with a 10kg weighted hand packer per square decametre in a radial pattern from center to perimeter. )

4. Lay down a permeable filter cloth, (better know as "road bed fabric") and then cover with a 100 mm lift of 10 mm to 20 mm crush and screened (cleaned) stone.

5. Now you are ready to select you grinding system to attach the hydronic tubing to.

If your tiles or flagstone are thicker than 30 mm you do not need to bed them in anything but sand or "stone dust" as they will form a solid matrix if laid with tight fitted joints, otherwise you will need to go through the extra burden of bedding them in a lime mortar bedding.

There is a number of ways of doing this, some better (only slightly) than others. Some are recommending a layer of "10mm thick radiant non permeable insulation" under the hydronic tubing. The "jury" is still out on this one as whether it does anything or not. I do not believe it really does and have not seen any "independent" lab testing to prove me wrong. Since these "radiant barrier" when used in walls are considered not as or to have little effect if they are "dirty" and/or do not have a 20 mm "dead air space" between them and the interior heated/cooled space. A 50 mm layer of polyiso or other urethan foam between the large stone and the smaller stone layer is effective at retarding heat loss into the ground. However, it also blocks cooling effect from normal ground temperatures during warmer months. Most heat loss is through the roof, then walls and a very little through most floors system. Drafts are you biggest "temperature drain," but don't go for "air tight."

That should give you something to chew on...and ask questions about.

Regards,

jay

Now we're talking!!! Thankyou thankyou thankyou!!! Now the very first question is .....what do we use for the foundation support? Lime mortar ? Only one wall has no foundations .

what do we use for the foundation support? Lime mortar ? Only one wall has no foundations .

Well what you will use depends on the wall. If it is a masonry wall, that is going to be a real challenge if you are not an experience mason. I am, and I still will not destabilize the wall without our PE involved. If it is a "timber and cob" wall, then it should have a sill or plinth stones holding of the timber frame above. This wall needs to be "strengthened" with "shear plates" and "strong back" temporary bracing, before undermining the wall. You could also just leave the foundation under it alone and use the appropriate angle of repose and slop the current material at that angle. Undermining a wall is a challenging thing to do and rebuild under the best of circumstances.

Yes use lime mortar if stone foundational elements are stone.


When you say a wall "has no foundation, what do you mean?


What is the wall built with, and how? What does it rest?

Great, the wall is cob and bits of stone but not many. The other side of the wall will not be dug down, that will remain as it is. Current investigations suggest it was sat on just the earth...... Though I have to be honest we haven't pulled back the earth in any more spots for exactly the reason you said! So I will do what you suggest thankyou!!! Make a sloping support using lime etc and fence in the earth wall.
Will post photos when we have done it. Thanks jay, you have been incredibly helpful and informative!! And with those details my husband is happy too!! ;)

If PE means a Professional Engineer, then its essential to use one that is sympathetic to the materials.
I am a Professional Engineer and most of my peers would not know what to do about your job and would push for concrete.
As Jay has explained that would result in the ultimate destruction of the building.

So take care in who you listen too.