Sand cement Floor Screeds

[Ajax123]

As it Is likely to be dirty particularly with dust a light sanding to loosen any racked in dust followed by a good vacuum clean is appropriate. Do not wet clean it.

Then prime it using a standard acrylic primer. Bond it will undoubtedly have one available.

As you are using granite which is a natural stone it is also appropriate to use an uncoupling membrane such as Ditra or Durabase. This is a recommendation of the stone federation.

Your screed dimension is just about at the point where it should have a movement joint it based on the depth and overall size you will probably get away without one but to remove any long term risk of movement cracking uncoupling becomes more important. Looking at the size this should not add a significant cost to the job but will save you the grief of cracked tiles later on.

 

[Mark S]

John,
As per most of the advice already given, unless the screed is a polymer-modified screed that has hydraulic binders in, then stick to a minimum of 28 days before even considering laying tiles on it.
There are numerous de-coupling mats available, but take advice from each manufacturer.
The BS recommendations do state 1mm per day ave. drying, this varies on each site condition.
hope this helps.
Mark S, Technical and Specification Manager, Gyvlon Ltd

 

[bugs183]

Ajax is your man for screed advise as said above!
If you're going to uncouple the floor i'd certainly use Ditra matting, we've been using for nearly 20 years and i'm as confident in it now as ever, i've used Dural on a few jobs as it was supplied, but i've got very little confidence in it, the Ditra feels and performs as a far superior product.