Limecrete and Altro?

[Keithj]

May I check that I've got this right...

We're working on the plans for a kitchen and a loo at the back of the church, inside the (unused) west end. It's a Grade I 13th century building, with various additions and alterations through to Victorian times. We're almost ready to submit the faculty application (the ecclesiastical equivalent of LBC).

As far as we know (we've not started digging yet) the floor under the area we plan to use is earth. Everywhere we've dug so far has been joists over earth or bricks/pamments laid on earth.

The architect plans to dig down and pour a limecrete base. The initial plan was above that to be Altro (a waterproof easy-clean flooring, ideal for the location and use). He is now worrying about the effects of damp, given that the Altro is waterproof, and says we should use bricks instead. I don't think a brick/pamment floor is ideal in a kitchen area like that. Given that the kitchen area is immediately inside the walls (stone, depth unknown but must be significant given the height and size of the building), is damp likely to rise up through the limecrete and have problems with the Altro? There are no damp patches there today; the existing floor is wood, on joists, with ventilation holes at the sides, and with Marley tiles (don't ask!) on top. We have an asbestos report and the contractor knows the score on that.

The limecrete will extend beyond the kitchen area, where the surface aboce it will be brick. The sequence west to east will go: outside stone wall; limecrete and Altro for 3 metres; limecrete and pamments for another 5 metres; earth and pamments thereafter.

My reckoning is that the amount of damp likely to rise up through the limecrete is not going to be significant, and that it will have an escape path via the pamments adjacent to it. Another of our group wants to put a DPM under the limecrete, but I can't see that helping much. What does the panel think?

Would joists and a wooden floor above the limecrete (with suitable ventilation) be needed?

 

[MatthewC]

Hi Keef

Well, we are just starting to do almost exactly the same task in the west end of our 900 year old Grade I listed church - work commences on March 3rd!

I've never heard of Altro. We are using unsealed Creeton limestone tiles (20mm thick) over a limecrete base, acknowledging that some staining may occur but so what? The limecrete floor allows moisture to evaporate; anything that prevents this will cause a build up which may become so much as to be permanently damp (which has to be bad news). A DPC under the limecrete would certainly prevent that evaporation (and so one might as well use some cheaper concrete), so a DPC is a complete no-no, as is sealing the floor.

When we can afford it, we will replace the entire floor with a limecrete base and the same limestone tiles, thereby undoing the work of the Victorians who lowered the floor level and caused lots of damp problems in doing so, as well as introducing a variety of levels which make DDA compliance impossible. (Yes, we do have permission...)

Matthew

 

[Keithj]

Thank you for that!

I phoned Altro: the first person had never heard of limecrete, but had one of their field experts call me. He knew limecrete, and said what you've said - absolutely no DPM, and probably not Altro either, although they do have a product for areas with a high RH.

If there's a high RH, I think we'd want it to be well ventilated, so I'm coming round to the same conclusion: either a limecrete floor surface, or something permeable on limecrete. A ventilated wooden floor may be another option.

 

[plasticpigeon]

Hello Keith. I have discussed these things with Ty Mawr who i believe invented the modern limecrete floor concept. I was worried about sealing my quarries with linseed oil. I wanted to do that as it evens out the colour, but i did worry about whether it would stay "breathable". The technical chap said that it is not only the ability of the floor to pass water vapour that was important, but that the foamed glass aggregate and thick limecrete slab on top of that act as a moisture buffer, allowing moisture in the earth into and out of the mass of floor. therefore the ability of the surface to allow passage of water vapour is not of paramount importance. Not what I expected. How much of this is correct is anyone's guess!!!!

 

[Flyfisher]

Hmm. So what's the difference between a 12 inch slab of limecrete or an extra 12 inches of earth?

 

[plasticpigeon]

I think that Ty Mawr were saying that the thickness of foamed glass (about 200mm) doesn't allow water transport by capillary action so it will not get soaked by liquid water, but will allow vapour into the voids around the foamed glass briquettes, and also into the lime slab. this will act as a buffer for water vapour that has evaporated from the wet earth lower down. This would mean that the wet earth is butting up to the walls much lower down the wall. Who knows?

 

[Keithj]

Thanks for all the received wisdom!

I had a pow-wow with the Churchwardens this evening, and we've gone off the idea of Altro (which will no doubt upset the architect, but into every life a little rain must fall). The options look like a permutation of limecrete surface, some form of stone (I'd not heard of Creeton, but will do some research), or whatever alternative the architect comes up with.

The architect was planning to lay the limecrete directly on the earth, not foamed glass aggregate. I'll do some reading up on the Ty Mawr website!

It's a good education in here, innit!

 

[MatthewC]

The architect was planning to lay the limecrete directly on the earth, not foamed glass aggregate. I'll do some reading up on the Ty Mawr website!

Your architect needs educating. Having had a limecrete floor installed in my house, I was delighted when the church architect proposed almost the same design for the first bit of the church floor (except she had RFG instead of LECA). It's a sad thing that so few professionals understand the subject even when they are specialists in old buildings like churches.

Creeton stone is quarried at Ancaster and the buff/honey stuff looks lovely. When we laid it there was an argument about sealing it; I listened for about ten minutes and then explained why we shouldn't seal it. Later on I mentioned this to the DAC secretary and said that the approval should specifically forbid sealing - she replied "I thought it was obvious!"

 

[Keithj]

Thanks again. Yes, the architect is in for some explanations when we next meet! I didn't expect to find that I know more about the subject than he does.