What is the best substrate before tiling over a new concrete screed?

[Soyabean]

Hi there, I am approaching the end of a rear extension which is going to have a concrete floor. I have just had the web underfloor heating pipes laid and tomorrow a 75mm concrete screed will go over the whole area. We want to have the area tiled and I am researching what the best thing to do is before having the tiles laid? My builder is advising me to purchase Durabase or Duramatt membrane (that's what I think it's called) which from what I gather is a 3mm membrane which comes on a roll. He tells me that it is best that such a product is put down before the tiles are laid. But seeing that this is a tiling forum I thought I would ask the experts in the field for there opinion!
Hope you can help.
Cheers
Sel

 

[faithhealer]

good advice from your builder

ps welcome to tf

 

[Scott]

Welcome soyabean

Its nice to see that you have a builder with some good knowledge on the right prep!

What tiles are you thinking of putting down?

 

[White Room]

Hi and welcome

Good builder

 

[DHTiling]

Hello Sel and welcome.. This membrane will cope with new screeds, as in shrinkage.curling and also with this membrane your tiler can tile it quicker as less waiting time for the screed to dry as the membrane is also a vapour equalisation membrane.. but what we do advise is that the heating is commissioned first before tiling commences... speak to your screed supplier as to the time delay required to add the heat..

 

[Soyabean]

Hi all and thanks for your replies. We will be putting porcelain tiles onto the screed. I have heard but forgot about commissioning the under floor heating to make sure the screed thoroughly dries out. Thanks for pointing that out.

My next question is, is a membrane really required? I spoke with a tiler who said as long as you use a flexible adhesive then it's not really required. And by adding the membrane I will be doubling the amount of adhesive I will use.


I know that my builder paid extra to have fibre bits added to the screed which is supposed to make it stronger.

I could certainly do without having to fork out for it if I don’t' really require it? But of course if it really is required I will do it. Your thoughts really appreciated

 

[diamondtiling]

You do need it and it wont double the adhesive requirements. Listen to the builder, you seem to have a good one.

 

[Soyabean]

Hmm okay thanks diamondtiling. Can I ask what could happen if I didn't and do you use the same adesive for fixing it before tiling over it? We have had the web underfloor heating installed into the screed btw not the electric one. Thx

 

[aph257]

good advise from your builder and above.

 

[diamondtiling]

Under floor heating in its very nature will create extra movement in a floor as it heats up and cools down. You might never have a problem if you dont use the membrane but problems have happened in the past and that is why these products are designed.
You should take the advice offered and install a membrane.

Ps same adhesive, smaller trowel to fix the membrane

 

[Soyabean]

Right so it sounds to me that membrane it is. A quick adhesive question. Is GRANFIX a good make or adhesive to use? It seems to be quite reasonable for the 20KG flexible bags online.

 

[diamondtiling]

I haven't used Granfix for ages so cant really comment. I use Mapei and Ultra, if you have a Tile Giant near to your location you may get a bit of a discount just by being a forum member.

Every little counts...tap tap.