Thin bonded screed over concert base

[jonnyc]

Still trying to find most cost effective way to to straighten out a concrete sub base in a church before laying French limestone.
need to make levels up between 0-20mm in places .
i could bed stone in mix of plastering sand white cement and adhesive but I can not give a guarantee with this method even though done many many times with old stone floors plus going on top of ditra which only made up to 10mm bed.
there will be a liquid resin Dpm going on top of concrete.
what does anyone think of a thin bonded screed before tiling and if so how thin can you go and do you know a specialist who would undertake this in ascot Surrey.
Area is 320 sq mts

 

[Ajax123]

Still trying to find most cost effective way to to straighten out a concrete sub base in a church before laying French limestone.
need to make levels up between 0-20mm in places .
i could bed stone in mix of plastering sand white cement and adhesive but I can not give a guarantee with this method even though done many many times with old stone floors plus going on top of ditra which only made up to 10mm bed.
there will be a liquid resin Dpm going on top of concrete.
what does anyone think of a thin bonded screed before tiling and if so how thin can you go and do you know a specialist who would undertake this in ascot Surrey.
Area is 320 sq mts

try a company called Churchill Flooring based in the midlands. They do all sorts of specialist floor types and I'm sure would come up with a solution that you could guarantee. Tell them you got their details from Alan Jackson and try and deal with either Steve or James.... I do lots of work with them.
Churchill Flooring Screed, Under Floor Heating, Concrete

 

[jonnyc]

Alan thanks for this. I had forgotten you had recommended me to them for a very big job in London and they were vey helpful .
hope to get them involved if that comes off .
will call them monday

 

[Aston]

hi jonny
theres also csc screeding. Floor Screeding Contractors London, South East and UK - CSC Screeding they can handle that no problem. take a look at there site , might give you a few ideas

 

[White Room]

Ronafix do similar materials http://www.barbourproductsearch.info/Ronacrete-Ronafix-screeds-TD-file017482.pdf

 

[Ajax123]

A liquid DPM would not be suitable in this instance. They are designed for use to prevent residual moisture issues not rising damp issues which is what you will have here. You would be better to avoid cement if possible and use a lime based mix. If you had the depth you could put a polythene DPM in and use a cement based aced but you don't have the depth in this instance.

 

[jonnyc]

The Dpm have been looking at is f ball 75 . The concrete base has no Dpm and the existing wood block had dry rot which has now been removed.
have had a hygrometer on in various parts of floor and had readings of 85-92.
Have been advised that I could prime base with p 131 diluted then green bag and 114 bottle thin layer to smooth floor . Then f75 followed by neat p 131 primer and then make up floor difference with green bag 114 and granite clippings followed by ditra . Is this wrong?

 

[Ajax123]

I'm not the expert on f ball and co and if you want to stick with their advice that's fine. They have to warrant it not me. However. Your rh readings mean nothing really because as soon as you cover the slab the moisture level will rise. This cold cause a phnomenon called osmosis which will cause bubbles in your DPM over time which could ultimately lead it to fail. Also the rising damp will contain soluble salts of unknown origin and nature which could have an effect in the DPM. Far better to use a loose membrane that will allow moisture to circulate underneath it.

 

[jonnyc]

alan the problem is that they do have enough height to play with . if it is an unbonded screed doesnt it need to be min 65mm.
the architect started off down the ditra route straight on to concrete but this will not remain stuck i think , plus problem of max 10mm bed over ditra.
it seems there are countless companies doing resin dpms .do you think that they are meant for different purpose than my scenario.
i have spoken to ardex.laybond,instarmac,ball and they all have a similar product dpm they say is fine .
it gets very confusing.
i guess the answer would be if could have a thin unbonded screed on loose plastic membrane .
here are some photos of what we have got now

 

[Ajax123]

The amount of white salts is testament to the moisture moving through. Tell me.....why did they remove the parquet in the first place.

Also something just popped into my head from a past life. There is a company in London called John Newton membranes who specialise in moisture management for this type if thing.

Im also wondering if a boarded solution might work. E.g. Scabble the concrete properly, stick 6mm hardi down and screw it then ditra then tiles..... The hardi will be unaffected b the moisture and the ditra will stop it coming through the tiles and allow it to dissipate.

 

[jonnyc]

alan they removed the the wood block because they had dry rot.
the thought from others is that this was caused by moisture coming up through holes cut in slab around columns and along the sides of walls .
concrete is quite uneven and way out of level and would need to be latexed first.
i will look up john newton . any help or thoughts much appreciated.
i ahve no problem with laying the stone floor. its a great job but this prep of subbase is out of the norm for me and i would rather they get an expert in who can deal with the moisture problem and screeding so i can then do what i quoted to do and have been accepted to do.
ie lay ditra mat and stone

 

[Mark S]

Jonny,
You have been given some good advice for the forum members.
Before you start have a look at the Mapei, Triblock P, designed for damp substrates, they also have a range of leveling screeds that could be applied on top to provide a good finish before you tile, they will write up a spec for you as well if you ask, they will also suggest their tile adhesive and grout!!

 

[Ajax123]

The triblock p looks like an interesting option. I would need confirmation of its suitability with rising damp from Mapei first and the on create will need to b thoroughly prepped first but looks worth a phone call at least.

 

[jonnyc]

mark . i will check this out now . if alan fancies it as well we could be on to a winner. are you connected to mapei .
i see you are on distinguished road which by strange coincidence i am too.
i have never seen this till now, what is all that about.

 

[Mark S]

Jonny,
I worked for Mapei for 4 years(screeds and levelers), so am familiar with the screeding products and some of the more obscure ones like Triblock, but do take advice from them.