lafarge low laitance screed,tiling with 600x600 polished porcelain

[deankyall]

job of 135m2 on low laitance screed,am i correct in saying ,does not need scarifying,just hoover, prime with suitable acrylic primer 1-1,second coat neat,mapei rep said today use primer g,then keraquick,check moisture content,when correct ,just tile 40m2 max bays,client didnt want any expansions!!!,i wont do without,so he wants just Silicon matching colour joints.

Any other suggestions would be appreciated thanks

 

[Ian]

How long has the screed been down mate, and what thickness is it?


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[Gazzer]

You may still need to sand the floor. I wouldnt be using that method either , Gypsum adhesive for me.

 

[deankyall]

guys ,ive talked to reps today,one said he had been to 9 failures in the last year,3 of them were gypsum adhesive,so i dont buy into that,im sure as long as prep and drying time is done correctly,cement based should be ok,mapei havent introduced theirs into this country,as they see no need,just saying what i was told.i can see the point of maybe an epoxy primer,as this stops the reaction between the cement and the screed,
also reading more on here from the lafarge guy , also says this type dosent need scarifying??

 

[Gazzer]

I think you will find that Alan says " It may not need sanding" The last 3 Low laitance screeds I have done all needed it.

 

[jay]

http://www.tilersforums.com/tiling-...r.html?highlight=lafarge+low+laitance+screed,

 

[deankyall]

right,how did you determine it neded sanding,scrape the top ,if its soft then is that it?
This is an example of whats wrong with the tiling industry, you try and do the correct method ,but there seems to be different correct methods according to who you speak to,after speaking to the reps of top adhesive companys i felt confident this was the way to go,i mean if you cannot count on these people,whats the point,isnt it about time that the industry as a whole got their act together and put some solid guidlines down ,by this i mean all the adhesive companys and screed suppliers etc? then we can all tell the customer "this is what you have to do" no ifs or buts,instead they are confused by differing opinions from different people qouting for the work, its getting to the stage where people dont want to take work on because if it goes wrong your in the deep stuff,****es me off,
the customer had no clue whatsoever about the implications of tiling onto this at all,so not told,then gets a shock when i tell him ,especially cost.

 

[Andy Allen]

any underfloor heating?

 

[deankyall]

yes gyvlon floor,the low laitance version

 

[deankyall]

yes underfloor heating too

 

[Ian]

Ok I'll give you some direct info from Alan (Ajax123), when I did my first Gypsum screed I called him for some advice and he said the the low laitence screeds need a scarify but, not anything to severe, just key the surface, then hoover thoroughly and prime. Now this next bit of info is from personal experience, I sampled cement based adhesive and gypsum based adhesive (with appropriate primers) on the same floor and the tile fixed with cement based adhesive popped up with a scraper after 72 hours! I know all the big manufacturers claim their cement based adhesives will adhere to gypsum with the correct primer but I know for a fact that thy are NOT as successful as gypsum based adhesives. Alan has (his words) seen many failures on anhydrite screeds and not one has involved a gypsum based adhesive. Please listen to this advice, it is well informed and is from direct experience, yes cement based adhesives will work on gypsum screeds but they are, categorically, never ever going to be better than gypsum based adhesives.

 

[deankyall]

is there a way i could contact him,then i could maybe get the customer info from the horses mouth

 

[Gazzer]

You can PM here View Profile: Ajax123 - tilersforums.com | Tile Forums | Tiling Forum

 

[Rich]

The advice given above is spot on. I tiled a few of these screeds over the last year or two, they are not to be taken on lightly. The prep has to be carried out correctly. The gypsum adhesive I used was really good and the advice we are quoting was from the man in the know and not from some1 wanting to sell there product. If you can get your hands on some gypsum adhesive then get it and I would still give the screed a but of a scrape up. The expansion joints are essential.

 

[deankyall]

yes i just thought that so did it already,cheers though