Limecrete with existing concrete slab

[thebadger7]

Hi all

Hoping for some help.

We have a Victorian property that has a relatively old extension on back (solid brick), containing bathroom/utility room. The bathroom is tiled onto a concrete slab to make level with rest of house. Utility part is currently quarry tiles about 50mm lower. I've attached the current layout.

We want to raise the rest of the floor and make a bit warmer. Considering using limecrete, but it would be a massive hassle to remove existing concrete slab as we'd have no bathroom. So wondering if anyone has any experience using limecrete for part of a floor, buffering up against the concrete slab already in place?

We have a bit of damp in lower walls, so trying to help with that.

Thanks

Luke

 

[Cubist]

Hello Badger and welcome to this sometimes merry crew, albeit most of us are typically grumbling about something or other.

I'm assuming your plan is to use a bed of limecrete to bring the two floors to the same level?

If that's correct then the limecrete bed would be circa 50mm thick which sounds to me sufficient to support the kind of kit found in most utility rooms but I would be a trifle concerned by the quality of the bond to the underlying concrete and whether that may in turn result in cracking. Personally, I've never tried it but there may be some members who have and can offer more experienced input. I'm sure there'll be a few other contributors along soon.

Good luck,
Cubist

 

[noj]

As I understand it you want to raise the old/relatively original utility floor. Do you know what's under the quarries?

If it's something breathable (potentially just soil and maybe some sand) then lifting them, potentially excavating a little and adding a limecrete slab to match levels shouldn't cause additional problems.

If the quarries are good then it would be nice to re-lay them? Obviously need your slab level appropriate to accommodate, they could be quite thick...

Regarding damp, external ground levels and impervious coatings may be your cause?

 

[a twig]

Considered a suspended floor? Few airbricks?

 

[88v8]

As regards damp, limecrete will not help, but at least it will not make things worse.
Bear in mind that it will only be permeable if your new tiles are laid and pointed in lime, no tile cement, and if you do not seal them nor put anything like vinyl over the top.

Have you identified the cause of the damp?
If the concrete slab is the cause, adding another relatively expensive layer on top is not ideal....

Ivor

 

[Feltwell]

*Someone* on here a long time did put a limecrete strip in around an existing concrete floor, save breaking the whole thing out - they just broke out a trench round the edge. I thought it was Ivor (88v8) but as he doesn't mention it I guess not! Use the search facility and you may be able to find it.

I've got this treat to come in my downstairs loo, it's got modern tiles that I suspect are on self-levelling compound on top of Lord know's what - possibly original concrete (Victorians used concrete!). It's only a small room and I suspect I'll need to break the whole lot out and put limecrete in, then quarry tile on top. Walls are damp.

 

[elizabeth]

Good morning Badger,

we had a concrete slab butting up to cob and stone walls. We noticed our skirting boards in our lounge were rotten in certain spots and the dreaded gypsum was bulging away from the wall. There was also a smell of damp. We removed the very thick gypsum and discovered the bottom of the walls had been tanked with black tar and a double layer of gypsum. The wall was glistening wet in some spots.
We were concerned any moisture would be wicked up the walls from under the concrete slab so we looked into creating a ‘hybrid’ floor as we couldn’t afford to take up the whole floor and replace with limecrete.

We dug internally a trench about 15cm wide and same deep along the outside walls and used foamed glass beads glypor, forgive me if I’ve spelt it wrong, wrapped in a breathable membrane geotex and then we used a lime mix on top, levelled to the meet the concrete slab. It’s been a year on since we did this, our walls were also plastered with lime and we have had so far no issues. The smell has gone, the walls are dry and all seems okay so far.

There isn’t much information on hybrid floors but we got our best knowledge from Peter Ward’s advice to a homeowner in Ireland. You could create the trench using the above and raise the floor level as well.


Hope this gives some ideas.

 

[thebadger7]

Thanks for the replies everyone, very informative!

What's the consensus of putting in limecrete floor in a bathroom given the moisture levels? Is that all the more reason to use limecrete?
The biggest challenge I find is finding contractors to use lime based products, you need your wits about you! The long curing time is also a challenge, but not insurmountable.

 

[Cubist]

If there's a concrete floor in the bathroom already and you don't intend digging it out then there's no point using limecrete. That said, limecrete is a viable flooring material for any room..

 

[88v8]

*Someone* on here a long time did put a limecrete strip in around an existing concrete floor, save breaking the whole thing out - they just broke out a trench round the edge. I thought it was Ivor (88v8) but as he doesn't mention it I guess not!

Well it sort of was, in that we put quarries around the periphery of our new slab-covered limecrete floor so as to enhance the breathability, given that the floor ultimately breathes only through the tile joints.

Someone else took this to the next level by breaking out the edge of their slab.

Here's the floor, eleven years on, and my dippy plastering. You see how much more area of pointing there is around the quarries.



Ivor