Hi to All,
Has anyone tried a floating ply floor over the lousy calcium sulphate screeds? Although a builder this is the first time I`1ve used the product and unfortunatly did not get good advice. I`ve since discussed the subject with Uponor Technical( under floor heating whose training courses we`ve attended- no mention of the problem) Discussed it with the local technical side of the local screed supplier to the contractor ( The technical dept actually said that it was the first they`d heard of the problem!!!!!!!). Have spoken to Schulter Ditra technical about adhesives ( I`m aware of the necessity of removal of latitence and moisture levels) and they are getting back to me ( have got a missed call from them on the mobile so will call tomorrow).
SO what about a floating ply floor of minimum thickness to creat a barrier. Your thoughts please to a lowly idiot

Originally Posted by jddevel

Hi to All,
Has anyone tried a floating ply floor over the lousy calcium sulphate screeds? Although a builder this is the first time I`1ve used the product and unfortunatly did not get good advice. I`ve since discussed the subject with Uponor Technical( under floor heating whose training courses we`ve attended- no mention of the problem) Discussed it with the local technical side of the local screed supplier to the contractor ( The technical dept actually said that it was the first they`d heard of the problem!!!!!!!). Have spoken to Schulter Ditra technical about adhesives ( I`m aware of the necessity of removal of latitence and moisture levels) and they are getting back to me ( have got a missed call from them on the mobile so will call tomorrow).
SO what about a floating ply floor of minimum thickness to creat a barrier. Your thoughts please to a lowly idiot

You sound a bit peed off with this one. I don't really understand the nature of the problem. Do you simply want to stick the ply to the screed and then stick something on top of that. If you are looking to stick the ply down you would probably need something like a butadiene based adhesive such as sikabond TF54 from Sika products. or are you trying to something else. There are possibly better ways to do what you need to do.

Also why is it a lousy screed - has something else gone wrong or is that you are just fed up with not being able to get the info you want?

What advice did you get that you were unhappy about?

By the way - not being picky or anything but it is probably Calcium Sulphate and not sulphide.
I am pretty sure that Uponor would not have the technical expertise to advise you about sticking the flooring down and it may well be that the screed installer or the supplier themselves would be equally unsure as this is quite an obscure request and they know about substrates not floor coverings generally speaking.

Same query - ' a floating ply floor ' . Is that the finish covering product, and what is the installation issue? CS screeds may have speciifc issues regading tile bonding to them, but a boarding product floor over them - same as any other substrate, no? What are we missing

I had a problem with CS screeds a while back on a Tilbury Douglas site. They were hell bent on using the damn stuff as the screed subbie sold it to them based on the speed of installation....

I highlighted all the drying out issues but had a young buck, ladder climber as a project manager who had already made his mind up before I had even got the job, so in the CS went.

He had it in his mind that I would be tiling 4 weeks after the screed went in

Anyway, 14 weeks later, I got a bomb test done on the screeds which still showed a high relative moisture content - much to the embarrassment of the rock star PM SO in he swung with his latest brainwave....

.....'Why don't we screw fix 18mm marine ply over the CS and fix the floor tiles to that?'

The adhesive manufacturer, Mapei, looked in amazement but confirmed that as long as the floor was sanded and sealed, then the underside and edges of the ply was sealed and fixed they couldn't see any problem. Basically the moisture would be getting trapped in the screed, but as long as it didn't come into contact with the adhesive it should be OK

So this is what they did, and we fixed with Keraquick and latex plus and as far as know the tiles are still there - that was approx 10 years ago.

Firstly thanks to your input. I suppose as an oldy with a flat learning curve cynically whats to me a "new" product with all the sales patter fills me with apprehension. Anyway to try and answer your questions. Unfortunatly its the Tilers Forum that has created my uncertainty. Realising that it was essential as good practice to seal the flow screed surface I searched on Tilers Forum for the right product and discovered the pitfalls and the added expense in materials/labour to ensure a "satisfactory" but possibly not guaranteed result on a Calcium Sulphate Screed ( Whoops Ajax123 I did admit to being aged Ha Ha).I telephoned the techinical dept. of Bardons the local ready mix company through whom I had got a list of licenced contractors for their product) and the answer was that this was the first time they had been made aware of an alledged potential problem with their product. So no joy there. My inclination from Tilers Forum was therefore to use Shulter and following a lead from Tilers Forum phoned Boyden Tiles for a price and asked about adhesives. They suggested AF 200 so I phoned Ardex techincal. No they said use P51 primer (dilute3:1) then ardex X7R. but recommend I phone Schulters technical preferably talking to Ian Linston ( excuse if mispelt) with whom they are in regular contact and who coincidently apprently is a contributer to Tilers Forum. He`s on holiday but another member of staff would get back to me. As stated message on mobile so will phone today.
Regarding Uponors input this was simply me trying some lateral thinking regarding the uncertainty and potential long term problems created by CS screeds and looking at the heat loss as a result of an additional marine ply floor subfloor not incidently fixed in any way to the CS screed but literally floating ( possibly on thin sand bed (same as the Romans laid tiles) with peramiter expansion joints.
Finally as a small self employed old fashioned developer ( not a bunch of architects or get rich investors) I wear many "hats" and have to pull together sales patter and advice from all quarters ( Its for that reason I find forums such as Tilers such a superb source of independant advice). Incidently don`t get me started on ground source heat pumps, wind turbines or the Stirling engine ( under development in Denmark for domestic use in my case using a pellet boiler) new glazing products etc etc.
Sorry to go on- screed must have dried by now!!!
P.S. Where can I buy a moisture test kit??

Originally Posted by jddevel

P.S. Where can I buy a moisture test kit??

Do a google search for Tramex and you will find a tester but sit down before looking at the price.

If its a decent size job, get the adhesive manufacturer to do the test.

Mapei used to do them for me the price of bomb test kits is crackers daft...

Reference test equipment anyone tried this: Tramex Concrete Encounter CME4

Originally Posted by jddevel

Reference test equipment anyone tried this: Tramex Concrete Encounter CME4

These types of meters do not give accurate results on Calcium Sulphate screeds. The correct test for moisture in line with BS8204 Pt7 is the surface mounted hair hygrometer. These can be bought fairly cheaply from the likes of F Ball and Co. Don't buy a digital one as in my experience they are less accurate. The Hair Hygrometer comes as a kit and last time I looked they were around the £60 mark plus postage.

I take it from your last post that really all you are looking to do is tile the floor. There is no reason to ply the floor if this is the case. Or is there another reason for the ply?

As a further comment to my ramblings this morning I`ll tell you what happened today. Spoke to Schulter Technical who stated that they advised on achieving less than 2% moisture and removing the latitence ( which incidently I have since discovered as advised at this site-http://www.gerflor.com/data/document/gypsum-anhydrite-tis.pdf should have been ideally done after 2/3 days) That I should use Ardex P51 followed by Ardex S38. This proceedure was the conclusion of Ardexs` and Schulters` technical depts.following exstensive discussions etc on the subject of Schulter Ditra. Hold on a minute I said to Schulters S38 was not what Ardex tech. told me yesterday. Oh yes thats what you use. So back to Ardex tech. NO not S38 -thats for Germany. We use X7R!! AAAAAGH -pull out hair. Now to sanding what do you guys use/do. Looks as if having had the floor down for about three weeks I`ll need a respirator when I sand because of dust.

Originally Posted by jddevel

Firstly thanks to your input. I suppose as an oldy with a flat learning curve cynically whats to me a "new" product with all the sales patter fills me with apprehension. Anyway to try and answer your questions. Unfortunatly its the Tilers Forum that has created my uncertainty. Realising that it was essential as good practice to seal the flow screed surface I searched on Tilers Forum for the right product and discovered the pitfalls and the added expense in materials/labour to ensure a "satisfactory" but possibly not guaranteed result on a Calcium Sulphate Screed ( Whoops Ajax123 I did admit to being aged Ha Ha).I telephoned the techinical dept. of Bardons the local ready mix company through whom I had got a list of licenced contractors for their product) and the answer was that this was the first time they had been made aware of an alledged potential problem with their product. So no joy there. My inclination from Tilers Forum was therefore to use Shulter and following a lead from Tilers Forum phoned Boyden Tiles for a price and asked about adhesives. They suggested AF 200 so I phoned Ardex techincal. No they said use P51 primer (dilute3:1) then ardex X7R. but recommend I phone Schulters technical preferably talking to Ian Linston ( excuse if mispelt) with whom they are in regular contact and who coincidently apprently is a contributer to Tilers Forum. He`s on holiday but another member of staff would get back to me. As stated message on mobile so will phone today.
Regarding Uponors input this was simply me trying some lateral thinking regarding the uncertainty and potential long term problems created by CS screeds and looking at the heat loss as a result of an additional marine ply floor subfloor not incidently fixed in any way to the CS screed but literally floating ( possibly on thin sand bed (same as the Romans laid tiles) with peramiter expansion joints.
Finally as a small self employed old fashioned developer ( not a bunch of architects or get rich investors) I wear many "hats" and have to pull together sales patter and advice from all quarters ( Its for that reason I find forums such as Tilers such a superb source of independant advice). Incidently don`t get me started on ground source heat pumps, wind turbines or the Stirling engine ( under development in Denmark for domestic use in my case using a pellet boiler) new glazing products etc etc.
Sorry to go on- screed must have dried by now!!!
P.S. Where can I buy a moisture test kit??

typically the screed will dry at a rate of 1mm per day up to 40mm depth and then add 2days per mm for every 1mm over 40mm. This does depend on good drying conditions which is basically ventillate the heck with out of the screed to keep the air changing and moving. You can force dry it with UFH if you like and this is great but again needs plenty of ventillation. Because of it's high thermal conduictivity CS screed does lend itself to ground and air source heat pumps because they tend to run at lowere flow temperatures in the UK but I won't get you started on that eh!!
I have no idea what expertise Uponor could have brought to the table in terms of floor coverings. They are great at Underfloor heating and have
had some rudimentary training via myself some years ago but I think most of the people I trained have since moved on. Likewise in defense of the readymix company they are experts at manufacturing screeds and concretes not on what goes on top of them. Additionally the readymix industry is in turmoil at present due to the construction crisis and staff turnover is at an all time high with lots of new and inexperienced people floating about.

Originally Posted by merlecollins

If its a decent size job, get the adhesive manufacturer to do the test.

Mapei used to do them for me the price of bomb test kits is crackers daft...

Some suppliers still offer this as a service but the sampling can be a bit hit and miss so you need to be careful. Good cheap way of getting a result though. The correct test is the hair Hygrometer in the UK but due to time constraints lots of people use quick methods. Carbide Bomb is my second favorite and is actually the preferred method in Europe.

Thanks Ajax123 - todays problem is to do with the ACV we`re installing ( great bit of gear to provide hot water using the cold mains in) What they didn`t tell me was that the 18:26KW boiler purchased which is more than adequate for the 12Kw needed for the underfloor heating as designed by ourselves and Uponor needed to be upgraded to 68KW to ensure the thing runs at max. efficiency and can deal with the 4 ensuites. More hair pulling. Good job I`m semi-retired. Much more of this "new gear" and I`ll be in an early grave.

Originally Posted by jddevel

Thanks Ajax123 - todays problem is to do with the ACV we`re installing ( great bit of gear to provide hot water using the cold mains in) What they didn`t tell me was that the 18:26KW boiler purchased which is more than adequate for the 12Kw needed for the underfloor heating as designed by ourselves and Uponor needed to be upgraded to 68KW to ensure the thing runs at max. efficiency and can deal with the 4 ensuites. More hair pulling. Good job I`m semi-retired. Much more of this "new gear" and I`ll be in an early grave.

The price of progress is obviously 42KW - what a Bu**er!! And here is me thinking we were supposed to be gettin more energy efficient. Covering your screed with ply will seriously impact the UFH efficiency I would think as well.

Fortunately tiling it should be pretty straight forward. It is just a case of considering a few options in terms of primer and adhesive combinations.

Have you bought either of these as yet?

Hi Ajax123,
Firstly reference ply. Its was a thought regarding the adhesive problems in particular the absence in some cases of expansion joints -although there are claims that in most domestic situations these are not required- and the apparent dificulties withadhesives. It was just a possible idea to create a "break" betweeen the two products adhesive/tiles and screed by floating a ply. I acknowledge reference to heat efficiency but a ply as thin as 5.5 mm possible could be used without compromising the heating to much. Anyway it was just a thought all be it possibly a naive one.
Regarding the primer and adhesive- no not purchased yet-still researhing-any advice especially bearing in mind Ardex/Schulter fiasco referred to in my previous comment.
Another point any advice on sanding latitence ? Some of the floor is to have a 22mm engineered oak floor so a minimum deviation of level of 10mm over 3mtrs would be nice!! Do use an industrial sander (hire shop job) with a high grit number abrasive sheet or possibly a drywall sander ( for use on plaster walls - although my employee is good enough we don`t have to sand!).

Originally Posted by jddevel

Hi Ajax123,
Firstly reference ply. Its was a thought regarding the adhesive problems in particular the absence in some cases of expansion joints -although there are claims that in most domestic situations these are not required- and the apparent dificulties withadhesives. It was just a possible idea to create a "break" betweeen the two products adhesive/tiles and screed by floating a ply. I acknowledge reference to heat efficiency but a ply as thin as 5.5 mm possible could be used without compromising the heating to much. Anyway it was just a thought all be it possibly a naive one.
Regarding the primer and adhesive- no not purchased yet-still researhing-any advice especially bearing in mind Ardex/Schulter fiasco referred to in my previous comment.
Another point any advice on sanding latitence ? Some of the floor is to have a 22mm engineered oak floor so a minimum deviation of level of 10mm over 3mtrs would be nice!! Do use an industrial sander (hire shop job) with a high grit number abrasive sheet or possibly a drywall sander ( for use on plaster walls - although my employee is good enough we don`t have to sand!).

I'd advise against using ply in this way, even more so if you're thinking of making it 6mm! The advice from Ardex is usually sound - S38 is a flow out adhesive, for large format tile - Schluter got the wrong product - it wont work so well to put Ditra on. The X7R is correct - we would fix it in this way - and my advice for this is to use the Ditra system.

I agree with CBTC about the ply - was not sure yesterday but done some talking today and think it would cause you problems.

In respect of the addy you have a choice to make.

1 use cement based addy. If you go this way I recomend a water based epoxy primer rather than an acrylic. Seen too many failures with acrylic but none with Epoxy.

2. Better still get rid of cement and use calcium sulphate based addy. Price not too disimilar and you remove several risks
a. Ettringite Reaction - only occurs if cement there
b. differential expansion and contraction between cement based addy and screed

There are not many calcium sulphate addys in the UK but there are a few and where they have been used in Europe to a much greater extent the results have been encouraging. My colleagues in France tell me that they see almost no failures on calcium sulphate adhesive. This is my favorite option.

3. Use Decoupling mat - deffinitely the most expensive route

In terms of laitance - I suspect there is none on the screed you have but it willl need to be clean, dry sound and dust free to quote the BS. If there are mortar snots or paint stains etc they need to be removed by sanding. Typically it is a good idea to run a floor sander over it with a 60 grit paper. If you need to do any serious sanding use a copper disk.

The BS says it is reasonable to expect a surface finish to meet SR2 i.e. no more than 5mm deviation from a 2m edge. This is not difficult to acheive with this type of screed. If it is worse than this I think I would be asking why.

Ardex - very good products and tech advice sound but they dont do calcium sulphate adhesive. If you do use Acrylic primer make certain you put plenty on - 2 coats probably not enough.

Wow Ajax123 Great advice and much appreciated. As stated previously I suspect previous uncertainty created by "senior moment" although you`d think having been in the building trade for nearly 40 years and having seen most things I`d be mentally prepared for change/problems. But then perhaps previous experience has taught me that nothing well done is achieved easily and perhaps I`m nearer needing to completely pack up than I thought. Trouble is I enjoy seeing a house rise from the trenches.
Thanks Again to Ajax123 and all those who have helped.

No problem JD - I guess you are no different to anyone else in the respect that if you come across something new and different you don't know how to treat it. Then again if no one tells you how to treat it you can't be blamed for it can you.

Anyway - you will have a complete nightmare if Tilt Up construction ever catches on in the UK. They can build a house shell from digging foundations to completing the roof in about 4 days - phew....

Just cos it is easy don't mean it's bad

Anyway - I had a long conversation with Keracol Technical today about their gypsum based adhesive and they say the gypsum screed doesn't even need to be primed. Still not convinced myself so have asked them for some samples. Will probably report back through the Forums at some point.

Kerakoll h40 ideal looks like a good product for gypsum etc type screeds...

Lets hope all the other manufactures try and release these type of adhesives...

H40® IDEAL develops a high degree of insensibility to chemical attack of sulphates in substrates with a gypsum or anhydrite base, ensuring laying of covering materials without the need to apply an insulation primer. The innovative H40® IDEAL technology neutralises the expansive chemical reaction of plasters and screeds with a gypsum or anhydrite base, facilitates and speeds up the process of laying and establishes superior levels of safety, ensured by the use of anti-sulphate micro-components with a chemical structure specifically designed for adhesives.

Kerakoll.com

Originally Posted by Dave

Kerakoll h40 ideal looks like a good product for gypsum etc type screeds...

Lets hope all the other manufactures try and release these type of adhesives...



Kerakoll.com

I got them coming to do a presentation on this one and some other stuff they are doing. I agree that it would be great if the other manufacturers would come up with gypsum systems. Would solve a lot of tile hassles with CS screeds. I know some are working on it.

I know again might be a wild shot, but I`ve contacted Gyproc Technical, after all they produce plasterboard etc adhesives and may well provide some imput.
Will certainly be interested in the presentation results of Kerakoll h40 etc. - I`m getting quite in to this all now.Perhaps there is hope for me yet. In the meantime the floor is at least drying out!!

Reference the statement regarding "doesn`t even need to be primed" -like you Ajax123 am suspicious t-this is from Kerakolls` website Sounds like the salesman not knowing his product. Might be worth printing off and showing him/her. Couldn`t find spec. on their Primer A professional-unless I misunderstood their reference?
PRE

Do not use

On gypsum-base plasters and anhydrite screeds without the use of PRIMER A professional, concentrated, waterbase,
surface insulation product; on plastic or resilient materials, metals and wood; on substrates subject to continuous

moisture rising.
PASounds like the salesman not knowing his product. Might be worth printing off and shSowing the demonstratorRATION

Originally Posted by jddevel

Reference the statement regarding "doesn`t even need to be primed" -like you Ajax123 am suspicious t-this is from Kerakolls` website Sounds like the salesman not knowing his product. Might be worth printing off and showing him/her. Couldn`t find spec. on their Primer A professional-unless I misunderstood their reference?
PRE

Do not use

On gypsum-base plasters and anhydrite screeds without the use of PRIMER A professional, concentrated, waterbase,
surface insulation product; on plastic or resilient materials, metals and wood; on substrates subject to continuous

moisture rising.
PASounds like the salesman not knowing his product. Might be worth printing off and shSowing the demonstratorRATION

I agree with your suspicions at present. However I am awaiting information from their techincal bods to confirm. I know the Benfergyps says "does not need a preventive primer". I take this to mean it does not need a primer to prevent the migration of sulphates as there is no risk of ettringite. I still feel it probably needs a suction reducing primer. The GBTA from creative impressions does need a primer and in this case it would be an acrylic. I am wondering if the benfer one is loses something in translation from Italian. My thinking is that the others are the same. My advice is always prime with an approporaite primer whether it be epoxy or acrylic or SBR or whatever. I will stick with that untill I know otherwise.

I suspect Gyproc would not be very aware of the screeds side of things because it is a very specialised sector even though they are similar raw material bases. Although their chemists might have some idea. I think it is because we work with hard gypsum and they work with soft gypsum. (that's all to do with chrystal size and structure and a whole different thread)

Kerakol also do one called universal which is a tubbed addy and says does not normally need a primer. I have samples on the way of several of their adhesives for me to look at.

I had not come across them really till recently so not sure. I do know that in Italy they are much bigger than Mapei and that the founding directors are ex Mapei so I would have to assume they are doing. Anyway - will let you know.

Just found this on a previous thread started by Foxman last January
http://gutjahr.bpanet.de/uploads/tx_gutjahrprodukte/Watec2E_englisch_1.pdf
under the title of tiling on a decoupling mat. Seems the way to go if any doubt and a load of advantages over Schulter Detra. Anyone got any updates on the product?
Watec2E

Originally Posted by jddevel

Just found this on a previous thread started by Foxman last January
http://gutjahr.bpanet.de/uploads/tx_gutjahrprodukte/Watec2E_englisch_1.pdf
under the title of tiling on a decoupling mat. Seems the way to go if any doubt and a load of advantages over Schulter Detra. Anyone got any updates on the product?
Watec2E

Not come across this one in the UK - is it available?

Had a call back from Benfer Technical today about whether or not primer is required on Anhydrite with their Benfergyps. If the surface is completely sound and ust free then no primer needed. Does not exclude the use of primer and this should be used if the substrate is dusty or not sound. I think for sake of simplicity and peace of mind I will go down the route of prime with acrylic anyway.

The attachment attached might be of interest

Have "googled" and come up with one number 02087789000 will phone tomorrow. Also emailed the manufacturer asking for UK stockists.

Spoke to a company today about Watec2E. Trimline - Tiling Trims, Tools and Accessories Whilst the product may be a good one I think they live in a different world price wise to the one I live in. They started quoting £552.60 for a 30 x1mtr roll although I did get them down to about £375 for a quantity. Thats still a lot dearer than Schulter Ditra from Boyden Tiles although no initial fixing or real preparatory work- or so its claimed!

Wow - that is pricey!!

I don't really think there is much need for a decoupling mat personally provided the screed is not sopping wet when you want to tile. I still think acryilic primer and calcium sulphae addy is the way to go. The more info I get through the more convinced I become. Here are a couple of other options for you.