Limecrete flooring - what is needed underneath?

Hi everybody,

We're researching Limecrete floor (with radiant heating) for an existing log house where the floors need replacing, but we're a bit hazy on what is needed underneath.

Previously our thinking was we would be to dig out the old floor to the point where it is nice and compact, then add a layer of small rocks and then insulation such as cob slipped thatch, then put the lime mix on top of that. I'm a bit hesitant about doing this however as rocks are a bit pricey here and I'm wondering if there might be a better way.

Anyways, I'm sure there are many ways to go about this, but what is your preferred way of doing a limecrete floor? Do you use rocks? Metal grids to prevent cracking? What about adding other things to the typical mix of 1 part lime to 3 parts sand, such as clay or other fibres? How thick of a limecrete layer? Would love to hear your approach. Any tips would be greatly appreciated.

Cheers,
Rob

Hi Rob I,

Sorry if I dropped a ball with helping you...kinda spread thin lately...

I am afraid that what I might share now isn't much different than the other conversations Earth plaster walls and earthen floor renovation [work in progress] and Foundations to hold heat in cold winters.

What are you asking now that is different? What have I missed?

I still haven't been able to see that Google Maps link yet that you posted...it just didn't work for my...sorry...

Your current questions:

what is your preferred way of doing a limecrete floor?

I use wood almost exclusively as this is the most cost effective in most areas...Have you broken down you square meter cost yet of both of these side by side...including your labor?

If I did facilitate any under my direction it would always as a thick tile or paver system.

I have only co-facilitated folks that have chosen to do these and the minimum thickness I would suggest is 100mm, and they did have cracking issues.

You must have read http://www.lime.org.uk/limecrete-floor/ web page by now...yes?

Have you looked at all of these? Limecrete Floors...


Do you use rocks?

Yes

Metal grids to prevent cracking?

No

What about adding other things to the typical mix of 1 part lime to 3 parts sand, such as clay or other fibres?

Fibers yes, though you could get "fuzzing" and would need to sand smooth the floor. Hemp, hog hair, or recycled polypropylene are some possibilities.

How thick of a limecrete layer?

100mm minimum.

Regards,

j

Hi J,

Thanks for your time. I understand many people need your help!

What I wasn't sure of is whether a lime floor should be treated differently to a cob floor as far as the layers are concerned: insulation, rocks etc. I have read the link you posted already, from another forum you put it up in. Thank you for that. It sounds like the same approach.

If I did facilitate any under my direction it would always as a thick tile or paver system.

Is that because of personal preference that you don't like a lime finish, or is there a practical reason for this?

I have only co-facilitated folks that have chosen to do these and the minimum thickness I would suggest is 100mm, and they did have cracking issues.

Just to clarify here, are you saying they had cracking issues with 100mm? Or was that a little typo and you meant to say they didn't have cracking issues at this size?

Fibers yes, though you could get "fuzzing" and would need to sand smooth the floor. Hemp, hog hair, or recycled polypropylene are some possibilities.

We've got a lot of Typha / Cattail here we collected for cob - would this be appropriate to use as a fibre?

I use wood almost exclusively as this is the most cost effective in most areas...Have you broken down you square meter cost yet of both of these side by side...including your labor?

When I researched prices of timber for flooring it seemed expensive. But now you've got me scratching my head thinking I need to look again if you're saying it is typically cheaper. I haven't broken down all the costs yet - I figure before I look at the price I would like to get an idea of even what is involved options and compare the benefits.

Labor seems like it would be more intensive with lime, but that it would last longer. And when it is warmed up with radiant heating, that it would act as a thermal mass also. The thinking is that if we made a limecrete floor, then when we had the resources we could add wood later, and get the best of both: earthen and wood floors.

Could you elaborate a bit on your approach for a wood floor?

I will sit with my wife today (I need her to translate - I'm still struggling to search for stuff in Estonia) and see about wood prices.

Best regards,
Robert

Rob Irish wrote:Is that because of personal preference that you don't like a lime finish, or is there a practical reason for this?

Oh my...sorry if I inferred that...I would love a lime or earth floor in many design applications...It is the cost in both material and labor that drives it to the bottom of the list. I can mill local tree species of a lower grade into larger dimension joist, and incorporate this into a timber frame structure that could, support a soapstone (or other variety of stone) with radiant heat for the same price (perhaps less) than a limecrete floor. As the market grows this could well change...and that would be great.

In many areas, wood is still going to be the most cost effective, easier to install and service, and more environmentally sustainable. If one has lime stone close by and the skill sets or industry to work it, then there it could be more germane. I haven't found that yet, but would love to see it happen...especially for "grade floor" or below areas within building design.

I still would make pavers or thick tiles and not lay a monolithic slab...Slabs just lead to issues of all types from cracking to not easily servicing electrical/mechanicals that may be buried beneath them.

Rob Irish wrote:Just to clarify here, are you saying they had cracking issues with 100mm? Or was that a little typo and you meant to say they didn't have cracking issues at this size?

It was that they are monolithic, thick or thin, the potential is there, even if relief joints are cut into them. I have also see "crazing" in the finishes as well in some forms.

I would also note that I am a huge proponent of "disentanglement" in architecture and ease of serviceability. Monolithic slabs, no matter the modality, must be broken up to service anything that is under them, and/or just not as enduring as most "component based" methods. Even our most ancient of streets and roads are still comprised of small stone cobbles...not large stones...and these are 2000 plus years old. I also find that this method is more "user friendly" in as much that you can work at a pace that is often more manageable...on tile/paver at a time on a bed of well draining sand, small stone, or some other appropriate medium.

Rob Irish wrote:We've got a lot of Typha / Cattail here we collected for cob - would this be appropriate to use as a fibre?

Hmmm....that may work? Remember, lime is very caustic in nature so I would do a test paver as see how well is holds of to abrasion and abuse.

Rob Irish wrote:...I haven't broken down all the costs yet...Labor seems like it would be more intensive with lime, but that it would last longer...Could you elaborate a bit on your approach for a wood floor?

You must look at both your labor and some unit metric of cost (square foot, meter, kilo,...board foot...something.)

Wood floors, depending on species and type can last well over 500 years...perhaps not as long as a well made lime paver floor...yet acceptable.

I have been trying to find the time......to write up a Post on Maru floors. Traditional Korean maru (maru=floor) floors, one form being Cheongmaru 청마루 have been around for millenia, and some are even of stone and allow for radiant heat underneath in the form of an Ondol 온돌 , which is something else I am planning a post topic on.

If you haven't you should read this post:

Raised Earth Foundations

Warm Regards,

j

adventures in limecrete flooring
https://www.youtube.com/watch?v=ZO-m5uOURE0

Grand Designs S07E05 - Carmarthen Eco House (Revisited)

a limecrete floor poured in winter by builders inexperienced in limecrete



and for those who want to abstain from planning - a cautionary tale

https://www.youtube.com/watch?v=pJAYpbD7RGs

Grand Designs S07E03 - Medway Eco Barge

LOL

Th youtube account has been closed so neither of the links work.