linear staining to jura blue limestone - TilersForums.com

[jonnyc]

just come back from looking at a problem floor in cotswolds.
big slabs 2.2 x 1.2 mts i think .
I did not lay stone but i know the supplier adntheir client wanted advice.
no problem with fixing, but there is a dark mark through tiles as shown in picture.
the centre of these marks are 1000mm apart as is the ditra mat underneath.
this suggests that moisture has come up through where the mats meet .
i put an a protimeter aquant on dark patch and it read 950-999.
if imput it on other areas of slab read 650-750.
i know these meters are way too sensitive for stone as if i went by their readings i would never seal any stone , but it does at least read higher over dark marks.
i think this suggests a moisture problem rather than a stain on top of stone.
thing is i have never seen this before and it is quite odd.
i also know that that most people dont buy the jointing tape schluter sell which is mega money , they simply just butt mats together .
i myself have laid literally hundereds of jobs on top of ditra even when screed only been down a week without jointing tape , and never had this kind of marking show through.
I can only think that maybe there is leak in the water underfloor heating which is making screed permanently wet and more than vapour needs to escape.
would be interested if anyone seen anything like this. i couldnt remove mark with wexa and hairdryer and did not want to put lithofin asr on as stone hard and honed and worried about ecthing.

 

[DHTiling]

wow what lovely stone...


As for the ditra.. then if it is used to vapour equalise then yes it should have been taped but if the screed was dry then no need.... so i am with you and if the screed had quite a lot of damp then that could cause what they have .. as for a leak then that is easy to detect on the heating said as the pressure reading will be dropping.

 

[jonnyc]

yes dave its beautiful stone and you get fantastic ammonites in it.
im sure you know its german and comes in beige.
rainsco uses both colours alot it seems .
i probably only do two a year in this colour.
imagine having to lift one of those beasts up if you got the bed wrong.
yes youre right first question is to check whether underfloor heating pressure dropping and i did advise client to get plumber on that next week. forgot to mention in post.
but it does bring up an interesting point.
as said before i have never used tape unless when ditra used as tanking in bathroom.
even with moleanos,or really porous bathstone or cotswold the vapour of screed drying underneath has never shown up lines of moisture.
this jura is really hard as well.
i think there must be a bad leak for this to happen.
have you ever taped joints . that tape costs a fortune if doing a big floor.
to be honest i have never even ovelapped edges as my thought process says if moisture going to come up it will find a way unlees using belt and braces tape method.

 

[DHTiling]

personally i have not used it for vapour eaqualisation on screeds that are drying out.. but have on dry screeds... hence why i say that for moisture to vapourise along the underside then it must not have joint lines to escape into the tiling field.

Jura is a lovely limestone and as you say a hard one at that... i installed a beige floor not long back..

anyway.. i would see if it is leaking first..

 

[jonnyc]

ill keep you posted what the outcome is .

 

[Tony73]

agree with Dave, could be leak. Ihave done beige jura not long ago. and lots of blue jura last year, never had problem.

 

[rainsco]

what a nice floor! that sizes are really beasts!

i don´t know whats going wrong but the jura is sensitive. look at this photo.

do you see the darker edge on top of the wall? i match the plaster afterwards tiling to the level of the tiles. and the discoloration don´t go away because the plaster takes to long to get hard. now i learnd about this situation and do a slope of fast adhesive on top of the tiles and then do plasting. the only way to remove the wet stains is to bleach it. i know a report in the "fliesen and platten". there was a jura floor in a whole house and they had wet stains on the groats. the problem (they think) was the plastik in the adhesive because they ignorate the maturing time. they bleach the whole floor and the result was top. i try to find the report and look what products they used.

 

[jonnyc]

that mark looks like moisture ingress you get when grouting some stones . we call it picture framing.
for some strange reaso wich i have never worked out, if you leave it 3-4 days then apply lithofin wexa and give it a light scrub it miraculously dissapears.
it is a very common occurence.
starngely with some stones if you leave it drying out for too many days it is very difficult to get off.