Limecrete patio slab?

[tom.harrigan]

Hi

I'm considering laying a limecrete patio slab. I'm considering it for

2 reasons:

1. I have neither a damp proof course nor damp proof membrane in my house, and I'm concerned that a concrete slab next to it might cause some damp.

2. Sometime in the future, I may be able to afford a little conservatory on it, so I might as wall do the slab now while I'm working on the patio anyway.

I'd rather not risk causing damp, but I'd also rather not risk the slab not setting. I may end up putting a very small amount of cement in the otherwise 6 ballast to 1 hydrated lime mix.

Any thoughts?

T

[TMC]

Never even looked at limecrete before so Googled out of interest

I was not even considering replying to your post

However Google turned this up

I thought may be of interest

Tony

[tom.harrigan]

up

> which I thought may be of interest

Thanks for the link. Unfortunately they did not test the cheap stuff, ie. bagged hydrated lime. I have experimented a bit with it in mortar form, and it seems to go off eventually. I'm also not bothered how hard the limecrete sets - so long as it doesn't break up.

I suppose an alternative would be to leave a reasonable gap between a concrete slab and the house, and fill it with pea shingle or something.

T

[Fash]

up

> > which I thought may be of interest

That's because the cheap stuff is rubbish. Bagged hydrated lime generally contains a significant amount of already calcified material which will affect the final quality. If you really want to do it in lime based stuff then it's no good seeing it as the cheap option. What leads you to think that a slab of concrete next to the house will cause a damp problem anyway? Either use some proper lime stuff, or stick to concrete.

Fash

[Anna]

up

>>> > which I thought may be of interest

I have not laid limecrete so talking off the top of my head ...

I dont think damp need be a problem in this situation. Angle the slab to drain away from the house

Either make the slab with cement or for a lower carbon footprint make it with hydraulic lime. If your old floor is hydraulic then its good to have the same so they move in unison ... hm, not that floors tend to move much ...

Hydrated lime is not suitable for this situation, which is exposed, damp and will get hard wear

Anna

[tom.harrigan]

up

> >> > which I thought may be of interest

I'm not so much concerned with drainage as condensation. If I leave a plastic mat on the floor of my house, it gets slightly damp underneath. If I cover the floor with plastic (done by previous owner) then enough condensation builds up over the years to drive damp up the walls. Not a lot of damp, but I prefer none at all. I'm just a bit concerned that concrete might do the same but from the outside. The limecrete slab does not have to be hard wearing, as I will pave it with a natural stone.

I'm not sure what the problem would be with using bagged hydrated lime so long as it's fresh. From what I've tried so far, it sets in a couple of weeks, and you can speed that up by adding a little cement.

T

[The Natural Philosopher]

[e-mail] wrote: The

Then you are creating an impervious layer anyway.

Don't bother to lay a concree base for stone. I simply tipped hardcore & limestine down and then some gravel, smacked it down a bit and laid stone over it. I used mortar for that.

What IS advisable though, is to leave a gap between it and the house, to slope it away from the house slightly, and if you want to improve the damp situation inside the house, dig a moat against the house wall first, and a drain for it, and back fill it with shingle and hardcore.

My impression also.

[Anna]

I dont think you need be concerned, its only the butt edge which is impermeable and now the plastic floor covering is gone presumably there is plenty of floor surface to allow evaporation

The

A floor slab isnt a very testing situation so yes you will probably be ok. After all, where is the slab going to go? Some spalling round the edges perhaps from frost damage so maybe you should clad the edges in stone too

Dunno if conservatories are covered by building regs?

Anna

[Jason]

replying to tom.harrigan, Jason wrote: I added a little cement to my lime pointing once. It speeds up the setting but it makes terrible efforescence. Also the cement migrates to the surface of the pores and blocks them so it's not breathable

[Brian Gaff]

posted on July 16, 2007, 9:05 am

Brian and I thought I was the blind one...

[harry]

You have a rising damp problem I would say. Bad for the health as mould growths are promoted. Needs fixing.