Floor tiling....

[Mo-sizely]

Hello all.. this is my first post of quite possibly, a few!
Have been reading forums regarding older houses (im about to purchase 19th Century cottage) and have been convinced to go against my initial "builders" logic of installing DPC & DPM under the concrete (over earth) floors..... with me so far??
Anyway, I've decided to lay floors with terracotta tiles, on top of the concrete, but do i need to continue the "breathability" by using a lime based adhesive & grout.. is there such a thing? the local tile shop seems to think not...
Any ideas or help?

 

[Moo]

I'm a bit puzzled by the concrete you mention. Is it there already, or are you intending to put it there?

 

[Mo-sizely]

Sorry.. Concrete (Or possibly limecrete type) floor is already there. Currently carpeted so it cant be too wet...

 

[Flyfisher]

I'm a bit confused about your "continue the breathability" comment regarding laying tiles on a concrete floor as concrete won't be breathable anyway so I can't see it makes much difference what sort of tile adhesive you use - although I'd be very interested in any more-expert views because I'll soon be tiling a concrete floor as well.

Installing a DPC under a concrete floor will, of course, be a rather big job and - as I understand things - may not be entirely effective anyway because such a DPC may just deflect any dampness to the walls. I don't know the practicalities of retrofitting such a DPC under the walls but it sounds like a huge undertaking to me.

If you don't have any evident damp problems then I can't see that tiling the floor will make much practical difference to the performance of your concrete floor, whatever adhesive and tiles you choose.

That's my assumption with our concrete floor anyway.

BUT - your "possibly limecrete" comment is very significant as that would imply you do have a breathable floor, so the above comments won't really apply. I think it's very important to confirm exactly what sort of floor you're dealing with.

 

[Penners]

Welcome to the forum, Mo-sizely. Star Wars fan, are we? :wink:

I can't improve on what Flyfisher has said. If the floor is concrete that you plan to leave in situ, use any tile adhesive you like. There's no breathability for you to prejudice.

If it's limecrete, that's a different matter.

 

[Mo-sizely]

OK,
well there are a few assumptions...
ie, the floor material. The house is circa 1850 so im guessing that the floor is a lime based concrete. Is there a way of checking this, ie. something as simple as a piece of litmus paper on the slab? Lime would show up as an alkaline.. i think.. :? :?
The walls are solid brick/stone without a DPC & rendered outside & in. (again assuming lime render) There are no obvious signs of damp anywhere, so without dissecting the walls & taking a core out of the floor to send to a lab somewhere, i have to be thinking along the lines that the house is typical of its age & that the potential damp is dealt with by the lime plaster. and the fact that it would have been allowed to "breathe".....(am i making sense yet?)

 

[JohnB]

I think my house is c1850 too, but it had a serious dose of cement c1970. See http://www.periodproperty.co.uk/forum/viewtopic.php?f=1&t=11219 for the gory details .

 

[Penners]

im guessing that the floor is a lime based concrete. Is there a way of checking this, ie. something as simple as a piece of litmus paper on the slab? Lime would show up as an alkaline..

You're correct. The problem is that OPC-based concrete would also show up as alkaline.

I don't think the age of the property can be regarded as an indication of the materials used in the slab. Concrete could have been used in 1850 - Brunel used OPC in the 1820's. But of course it's also possible that the slab could have been added to the house much later.

I shall leave it to others who have a great deal more experience of lime that I have to explain how you might be able to recognise the material visually.

 

[robgil]

what colour is it? any pics? do you have any damp? are you sure there isnt a slate dpc in your walls?
edit - i have a thirst for knowledge.

 

[Mo-sizely]

@ Penners...erm, yeah, Star Wars is a bit of a passion... in fact youre possibly the first person in quite a few yrs of using my tag that has actually seen it !! (phonetic spelling.. too easy for some !)

The problem is that OPC-based concrete would also show up as alkaline.

That kind of stuffs up my chemistry session...

what colour is it?

Its covered with a rather nasty GLUED down carpet currently... i cant really ask the seller if she minds me ripping it up just yet.

do you have any damp?

No damp in the floors has shown up on the survey, but it also seems a bit vague in areas, i think the fella just used it as an excuse for a day in the country...

are you sure there isnt a slate dpc in your walls?

Nope ! ditto above... all walls are rendered outside so without having a sneaky chip away at the render, is there another way of finding out... (i guess if i take a moisture reading at ground level, then, say 225mm up that might be an indication...)

The house isnt a wreck by any means, but the sellers ex husband was a bit of a keen DIYer, (well actually a complete butcher, but his intentions were good...)

 

[robgil]

if there are no visible signs of damp then i wouldn't worry too much about it. i am no expert but if you cannot see a dpc in the walls then there may not be one , as far as i know you cannot bridge a dpc with render.
why does your builder think it doesn't have a dpc and why does he think it needs one?
ive got an old floor in my kitchen thats made of a lime based concrete , its yellow with a crumbly kind of texture , no dpc.

if you are not sure what the floor is made from then assume it is lime and lay the quarry tiles on some lime mortar , it wont do any harm , it is quarry tiles you are laying isn't it?

we call the person who 'restored' our 16c cottage Mr DIY man , i curse at him quite a lot on a daily basis , cement and 8 inch nails were the only things he had in his arsenal and he wasnt afraid to use them , oh and not forgetting the flat head screws , the ones that will never come out. my banister handrails were nailed onto 500 year old oak studs with 8 inch nails , the banister hand rails are now gone but the nails remain. :evil:

his catch phrase must have been ''that i'll still be there a hundred years from now'' , he definitely built things to last , except the solid extension that is so solid when the old house moves the extension doesn't.........

 

[Penners]

you cannot bridge a dpc with render.

Yes, I'm afraid you can, Rob. I'm not suggesting that this necessarily the case with Mo's house, but as a matter of general practice, rendering that bridges the dpc and goes down to ground level can definitely allow damp to circumvent the dpc. Rendering across the dpc should therefore be avoided.

 

[Mo-sizely]

Crikey, forgot what my original question was...
So it would seem that if it is a limecrete floor ( Ill have a little tug at the carpet when we visit this weekend) then a lime mortar would be the stuff to "stick" the tiles down with...

Next question... does anyone know of a cheap supplier of terracotta or limestone ??? :wink:

 

[Schoolmarm]

Don't jump ahead so far! If you price or buy anything it will turn out to be a concrete floor.

 

[robgil]

you cannot bridge a dpc with render.

Yes, I'm afraid you can, Rob. I'm not suggesting that this necessarily the case with Mo's house, but as a matter of general practice, rendering that bridges the dpc and goes down to ground level can definitely allow damp to circumvent the dpc. Rendering across the dpc should therefore be avoided.

sorry fella , what i meant to say was you cannot bridge a dpc as in it is not good practice to most likely resulting in damp walls. I cannot bridge a dpc because common sense wont allow me to , but i have seen it done in the past with huge damp issues for the walls owner.

 

[Moo]

To pre-empt Penners, may I suggest that all would have been clear if you'd said "should not" rather than "can not" ?

 

[Flyfisher]

Indeed. There are all manner of things that should not be done to period properties (or any properties, I suppose) but, sadly, this forum is proof that there is little that cannot be inflicted upon them.

 

[Penners]

Now honestly... would I be that pedantic?

Don't answer that.

 

[robgil]

i wish the fella who 'restored' my old cottage did it under the impression that he could not have done half the things he should not have done. Ha , I have not even started doing any work yet and i am already moaning about Mr DIY man.

 

[Mo-sizely]

My problem is the order in which i make the statements... firstly its a case of, i "can" do that, then after ive completely screwed it up, i "should not" have started that !