Old question but still confused....

[One Day]

You will really have to push and pull to get solid coverage, and make sure the adhesive is wet enough. And don't forget to back-skim!

 

[JimboD]

Good to know. will look into membranes.I was going to leave a gap round all the edges to accommodate expansion and obviously use a flexible adhesive, but didn't think lateral stress would then still be a factor.

 

[GoneGuy]

Will you be trowelling the back of the limestone as well? I personally would with a smaller notch trowel

 

[JimboD]

yes, was planning on troweling (or at a minimum at least buttering) the backs.

 

[JimboD]

Just looked into membranes on Impish's suggestion. A few rolls of durabase seems the best bet but adds 3mm to the depth. Hmmm, need to do come careful measurements tomorrow as i think 3mm membrane +4mm adhesive + 12mm tile might be too high for then being able to run the tiles flush into the bifold door edging strip.

Thanks everyone for the speedy replies!

 

[thickbed]

Just make sure the screed is dry enough to tile to and get the laitance removed before you do anything else

 

[thickbed]

Just make sure the screed is dry enough to tile to and get the laitance removed before you do anything else

 

[JimboD]

Arh yes, "laitance". I noticed the dusty film when the screed was first poured (didnt know the technical name) but over the past few months had assumed it had all come away with all the coming and goings, sweeping and hoovering. Will check tomorrow if its still there. Hopefully wont need to attack it with a rotary sander but knowing my luck....Better to check now though and sand if necessary, than have 5k of tiles lifting in a years time!

NB: The screed came from SouthernScreed and on their website they show a video of someone sweeping the laitance off with a broom!

So many steps - laitance removal - UFH cycle - moisture level - sealing - possible membrane - adhesive choice - tile sealing - expansion gaps etc etc etc. ALL of which many DIYers will have overlooked or got wrong 🙂

 

[Albert]

Just looked into membranes on Impish's suggestion. A few rolls of durabase seems the best bet but adds 3mm to the depth. Hmmm, need to do come careful measurements tomorrow as i think 3mm membrane +4mm adhesive + 12mm tile might be too high for then being able to run the tiles flush into the bifold door edging strip.

Thanks everyone for the speedy replies!

Ball and Mapei do 1mm mats

 

[JimboD]

1mm would help. Seems straight forward enough to install from Mapai YouTube video. Just adds more time and cost.

So given main room is 10x6m is the decoupling membrane essential when using 12mm limestone and UFH.