More limecrete issues.

[robgil]

I dont see why a mix of ballast and NHL would'nt make a decent limecrete slab , any ideas why people dont do it this way?

 

[MdB]

At a complete guess I would say building regs. If you replace more than 25% of the floor then you have to have insulation which for limecrete means leca. Otherwise I can't see a problem with lime + large aggregate. The breathability will be reduced a bit but I doubt significantly and it would be stronger. However, as you have noticed, people don't seem to do this so there may be a good reason not to.

 

[skier-hughes]

I made a limecrete slab for my greenhouse, doing just that, works quite well, maybe should have given it mroe time before using it, as it shaled a bit on the surface but other than that is still doing well.

 

[robgil]

Thanks guys. On the subject of insulation , if you removed the foil from cellotex would it still be better than leca? It would allow vapour to pass through, I think.

 

[MdB]

Nope. I don't think you will get much vapour through Cellotex (it is basically plastic).

 

[plasticpigeon]

I read somewhere that the leca will allow evaporation through it but will not draw moisture through capillary action. That makes sense I think, it is pretty porous and there will be arge voids between the individual pieces of aggregate. I would have thought that the leca would be more vapour permeable than the lime, but I don't know this!!!! I'm going to lay tiles on a thin lime screed on earth in my place as I don't want the expense of digging out and want to keep the subsoil as dry as possible by promoting evaporation.

 

[AMc]

I don't know anything about it other than ads in Green Building Magazine but Breathe™ Hemp Insulation might be a suitable alternative to using a foam board product?
http://www.hemptechnology.co.uk/insulation.htm
There site lacks the detailed technical application drawings that the big foam board manufacturers supply so I'm not sure how it would work/if it would work in a "slab" application.

In some circumstances you can argue with Building Control that there is no practical way to insulate, I've never tried and wouldn't want an uninsulated solid floor but if push comes to shove it might be worth a phone call?

 

[MatthewC]

I read somewhere that the leca will allow evaporation through it but will not draw moisture through capillary action.

I wrote that in this forum recently, but "through it" means "between the pieces" (ie. that applies to loose LECA as the sub-base below the limecrete slab). I don't know if LECA (either loose or mixed in the slab) allows evaporation actually through the little Malteser-like pieces.

With my limecrete floor in a listed building, I had no trouble at all with Building Control. I had to explain the limecrete/LECA construction to him as he didn't know and was genuinely interested. He accepted that he couldn't make me use modern stuff on a listed building and that whatever I did was better than what was there before. Very helpful (as opposed to the CO).

(I bet the mention of Maltesers makes Penners reach for a K**-K**!)

Matthew