I'm about to tile a new (layed 6 weeks ago) screed with Warmup UFH in it. Would Mapei Keraflex be a suitable adhesive, also will the screed need a primer, if so could you suggest a suitable one!

The tiles are 300x450 ceramics.

I’m also assuming the UFH will need to be heated for a couple of days then left to fully cool before I tile.

Thanks for helping.

Glen

When you say screed do you mean Self levelling compound or sand and cement screed ?

Originally Posted by Sir Ramic

When you say screed do you mean Self levelling compound or sand and cement screed ?

took the words right out my ..... keyboard

It's a sand and Cement screed.

The UFH should be fully commissioned and run before tiling. If there are no joints in the screed it is likely to crack on heating. If it does you might want to consider uncoupling. Generally the heating should be controlled by floor stats in preference to room stats. The screed should be clean dry sound and free from dust and debris and primed using I would suggest a simple acrylic primer followed by if needed a flexible cement based smoothing compound. This should be left for 24 hours minimum before applying tiles with a flexible cement based tile adhesive. It is not usually necessary to re prime the top of the smoothing compound but some do and some dont. I personally would not unless it is dusty due to over watering.

Thanks for the swift response.

Warmup usually supply a green bottled primer especially for their system.

Peeps it is this system..

Warmup | In Screed Floor Heating System | Warmup® In Screed Underfloor Heating System (WIS)

That's exactly the system I've got. I don't have any warmup primer, I was going to just buy a mapei one.

You say that I should use the floor stat to control the system, is it just trial and error to get the room to the desired temperature or is there a general rule of thumb i.e. 5 degrees lower than desired room temp.

I meant higher than desired room temp !

Mapei Primer L is the one.
I know people tile right onto the screed and it is most likely fine, but I have always installed a Ditra layer then tiled when going over in-floor heat....Just to be safe, but then I always go a bit more than is necessary.