Floor Tiles Lifting On Anhydrite Screed

[J Sid]

I believe that a anhydride screed should have a expansion joint at 20mt max length with a heated screed and will expand 8mm over that length, correct me if I'm wrong @Alex123. And the tiles expanding about 4.5mm over that length.

So the tiles will need a movement joint or 2 over that length, and if the customer doesn't want any then walk away as it will more than likely fail at some point in the future. If it still fails then the tiler can say 'its not down to me' as @Ajex123 says.

Movement joints though floors don't always have to be unsightly.

 

[Ajax123]

I actually haven't come across an instance where tiles have failed that I have been unable to explain. I have been to a lot where the explanation is not acceptable to the client or the tiler. I hear the phrase "i did it by the book" and " i used all the recomended materials" so often i have lost count. To be fair lack of joints in either screed or tiles is way down the list of issues. The most common is moisture. I.e tiles put down too soon and that is followed by or usually goes hand in hand with the use of acrylic primer and cement based adhesive. Thing is with anhydrite it doesn't behave anything like cement board screed in terms of shrinkage, movement or cracking. Not to say it never cracks....it does sometimes. Certainly the number of failures has plummeted since the advent of gypsum based adhesives and since Francis flower came into the market as a binder supplier and we offered advice at all stages of the project we have seen a lot of failures avoided. One of the biggest issues I find is the lack of knowledge not so much amongst the tilers but amongst the adhesive manufacturers. I still hear reps saying that you have to grind off the top 5mm or you have to scabble and that laitance keeps àppearing after the tiles are laid. All of these are wrong.

I developed the attached data sheet to cover flooring contractors and they have been generally well received. I think they are helpful but am happy to readdress it if you tiling types think they're not

Information Guides

 

[Ajax123]

I believe that a anhydride screed should have a expansion joint at 20mt max length with a heated screed and will expand 8mm over that length, correct me if I'm wrong @Alex123. And the tiles expanding about 4.5mm over that length.

So the tiles will need a movement joint or 2 over that length, and if the customer doesn't want any then walk away as it will more than likely fail at some point in the future. If it still fails then the tiler can say 'its not down to me' as @Ajex123 says.


Movement joints though floors don't always have to be unsightly.

Maximum bay length is indeed 20m. The level of movement depends on a number of factors. The coefficient of linear expansion is 12x10 to the power of -6 m per m per kelvin. In other words if you start at 15degrees c and you increase the temperature of the floor to 25degrees c it will expand by 10 x 0.000012m per linear meter (so x20 if its 20m long).
In other words not a lot.

To meet the British standard there should be movement joints between independent zones, where hot meets cold and across all door thresholds. These are not often put in and it rarely actually causes an issue.

 

[J Sid]

@alex do you or other suppliers of this product offer a "signing off" ready to tile service?

 

[Ajax123]

@alex do you or other suppliers of this product offer a "signing off" ready to tile service?

No. It is something we discussed some time ago but realistically we don't have the manpower. There are Six of us working for Francis flower binder division. We supply to around 80 depots and each of these could do an average of two jobs a day. We were always happy to respond to enquiries from tilers and clients and often do. We also try to maintain relationships with suppliers of suitable adhesives as well. We do what we can but like any low staff company we can't do everything. I personally take calls from probably 3 or 4 tilers a week. We also supply specification advice to clients which is fine for bigger clients like the major house builders and where tyhjis has happened we don't get issues. Unfortunately though there are so many jobs thgast we don't get to intersect with we can oknlky hope to help by making the right information easily availkable usually through internet. I been on here for wages as well which I like to imagine helps a bit.

 

[Ajax123]

Oops... I meant i been on here for ages....not wages,.. Chance would be a fine thing eh

 

[J Sid]

@Ajax123 Thanks for yours replies.
So an opening for someone with the right knowledge / training to go round all these job and sign them off as fit and ready for the covering to be applied.

 

[AD Ceramics]

I actually haven't come across an instance where tiles have failed that I have been unable to explain. I have been to a lot where the explanation is not acceptable to the client or the tiler. I hear the phrase "i did it by the book" and " i used all the recomended materials" so often i have lost count. To be fair lack of joints in either screed or tiles is way down the list of issues. The most common is moisture. I.e tiles put down too soon and that is followed by or usually goes hand in hand with the use of acrylic primer and cement based adhesive. Thing is with anhydrite it doesn't behave anything like cement board screed in terms of shrinkage, movement or cracking. Not to say it never cracks....it does sometimes. Certainly the number of failures has plummeted since the advent of gypsum based adhesives and since Francis flower came into the market as a binder supplier and we offered advice at all stages of the project we have seen a lot of failures avoided. One of the biggest issues I find is the lack of knowledge not so much amongst the tilers but amongst the adhesive manufacturers. I still hear reps saying that you have to grind off the top 5mm or you have to scabble and that laitance keeps àppearing after the tiles are laid. All of these are wrong.

I developed the attached data sheet to cover flooring contractors and they have been generally well received. I think they are helpful but am happy to readdress it if you tiling types think they're not

Information Guides

Is that not you want to hear "I did it by the book" or to the required specification.
Laitance removed, underfloor heating commissioned moisture tested correct adhesives etc etc etc, 90m2 kitchen floor no joint required unless it's a very narrow kitchen!!!(theoretically a corridor over 20m)
Explain what would cause it to fail, even you confess failures have plummeted since the introduction of gypsum/mineral adhesives, so there's still failures.
Stop trying to blind us with science........who is this Kelvin fella

 

[wayne]

The solo flex from benfer is a calcium sulphate based adhesive.

 

[widler]

Is that not you want to hear "I did it by the book" or to the required specification.
Laitance removed, underfloor heating commissioned moisture tested correct adhesives etc etc etc, 90m2 kitchen floor no joint required unless it's a very narrow kitchen!!!(theoretically a corridor over 20m)
Explain what would cause it to fail, even you confess failures have plummeted since the introduction of gypsum/mineral adhesives, so there's still failures.
Stop trying to blind us with science........who is this Kelvin fella

Even when the tradesman said he did it by the book, they can still blame it on something else, the problem is no matter what trade you are in if it goes boobs up the material manafacturerer will ALWAYS blame it on his mother brother sister or uncle , but never himself , they have yiu by the short and curlies, hell they can prove it with big words 😉