Leave it, limecrete it, or earthen floor it?

[phillc]

Hi all,

We've got a C18th cob cottage in Devon. It got 'improved' in the 1930s zeal to modernise rural housing - so we inherited all the no-nos: A good hard cement render, bitumous paint over the plinth, etc. All of which meant we also inherited a lovely smell of damp.

We've reinstated lime putty render (the cob was a right state - much emergency propping and chopping in of cob block) and the bitumous paint has been picked off the plinth and the whole repointed in lime putty too. Internally, all external walls are now back to lime putty. Even in the few months since this happened, and even in a super wet winter, it's drying out nicely.

But, I look down at my socks, and more importantly the cold feet in them, and my mind turns to the concrete slab floors; probably 1930s too.

They've got no damp proof membrane underneath as far as I can see. Mebbe the builder poured in some pitch, who knows.

I am not going to do anything urgent. The house has just had a major intervention. I'm going to let that stabilise for at least a year and reassess. I am, however, beginning to wonder whether it's worth taking out the slab in, say, eighteen months.

I am not especially interested in putting the house back like it originally was. I'm of the view that the 1930s alterations are as much part of its legitimate history as the original build. So, I am really only interested in change if it makes things better (hence removal of cement render etc). That means my easiest option is not to change: Add carpet, be done.

Or I can swap it.

With that in mind, what are people's actual experiences (looking to bias this thread towards lived experience rather than opinion, if poss) of:

Limecrete floors? I've heard the full spectrum from 'greatest thing ever' through to 'expensive con - they're basically NHL5 so little better than a concrete floor'.

Earthen floors? Can I really stick my sofa, table and chairs on them without sinking into the mud? Am I going to have to add annual reoiling of my floor to my (probably) annual-ish relimewashing of outside?

as replacements for concrete slabs?

Massive bonus points for anyone replying who has actually done this in a cob house

Thanks

Phill

 

[Kearn]

Whether your concrete slab has a plastic DPM is key really…

concrete can act remarkably well at moisture managing if laid directly on earth. Do the plastic bag trick on the floor overnight, weighted down and see if there’s a darker damp area under when you lift it.
If so, treat it like a traditional brick/tile/slab floor - only natural materials over, and allow it to evaporate. So, no carpet really - natural rugs with natural backing.
They polish up nicely too if you can find the right operator …

If there’s plastic DPM, then this is where walls can suffer as the ground moisture finds its way to the perimeter and into the base of the cob.
Not always the case though, as ever depends on your specific environment - in a previous house we had a thick concrete slab laid on plastic, no issues at all as the ground under was dry as a bone with us on top of a high point. I only dug it out as we needed to get levels back down, otherwise it was doing no harm as the plastic was sat on dust.

Limecrete floors, I’ve covered a few times in recent posts on here if you want to read through past discussions - short version, it’s nothing to do with the slab. However, those selling the systems run businesses selling lime and aggregates…
All the moisture management is in the RFG layer, which is the insulation and capillary break from the ground. The Europeans, where RFG originated and is sourced from, pop plastic DPM and concrete over. It’s used as insulation and a type 1 structural subfloor replacement. Just as it’s now recognised in the UK too by building control, for the same reasons, but not for its moisture management benefits. Therefore BC will still spec a DPM over it before the slab goes down.

Limecrete has its benefits and those who want to use it for other reasons, but moisture management is not a role it plays in the prescribed setup.

In order to benefit from the RFG though, you do need a good depth dug down…

 

[phillc]

Thank @Kearn for the reply - and sorry for the delay in coming back.

Yes, had read your previous posts - good to get your "as lived" experience too.

At the moment we're a bit of a builder's site so difficult to do the plastic bag test. I'd be very surprised if we have any sort of plastic damp proof layer though. No evidence of it but lots of evidence to suggest the floor we have is interwar, which I understand makes that much less likely.

No evident signs of damp rising up the walls either. Our plinth and cob are recovering from render-and-tar torture but they are *recovering*. Every day is a drier day than yesterday ... We're quite lucky as a we have negative foundation depth; our house is built on an outcrop of bedrock above the prevailing land.

Polishing the floor: Ooh! Now there's an option. I have lived in plenty of Victorian places with terrazzo halls. Ok, it won't be quite the same, but this is a good idea ...