Sand / Cement

[CDS]

Guys

Just been asked to tile the floor of a kitchen/breakfast room for a friend whose had a new extension built.

Main Floor is 10m x 4.5m and has been levelled with a sand / cement screed that went down last Friday. The screeds 2-3 inches thick - How long do I need to leave the floor before tiling? Am I right in thinking 4 weeks, or way off the mark??

This will eventually be a tiled multiroom layout running into a 16m.sq dining room and 12m.sq utilty / shower room - Do I need expansion gaps? (it's solid substrate so I'm thinking no, but having doubts hence I ask...)

I specilise in bathrooms so this size of floor is a bit of a novelty for me - I'm a bit out of touch with the requirements! Appreciate your advise.

Many Thanks. Chris

 

[White Room]

Hi Chris
Screed is 1mm a day, I would put a control joint thru the doorway, its where they normally stop and restart a screed

 

[Ajax123]

Sand cement screed should be laid with aspect ratio no more than 2:1 so 10m by 4.5m is right on the border line of requiring a joint in the screed. It is not so much to do with expansion but to control where the screed cracks due to drying shrinkage. I suspect in reality if the screed has been batched and compacted properly you will get away without splitting the screed up. If you do decide to joint it the joint can be retro fit by simply saw cutting the screed. This joint would need to reflect through the tiled finish. If however there is underfloor heating care is needed and I would refer it back to the householder to check what he wants to do. Whitebeam is spot on with the door thing. This is a classic restraint point and if there is no joint here the screed could crack later disrupting both the tiled finish and the screed itself.
In terms of drying time, Again whitebeam is right, you should allow 1mm per day in standard drying conditions or alternatively use a surface DPM such as Tremco Universal DPM or Laybond Onecoat DPM or of course one of many thers available to trap the moisture in. A moisture test before you tile is essential. The DPM's can generally be used when the screed is still pretty wet.