Tiling on new screed

[UgsDIY]

I have just put down 75mm of screed which i have fitted with underfloor heating pipes, i am aware that i cannot have the heating switched on for about 4 weeks to allow the screed to dry but my question is...can i lay my floor tiles before this time or do i have to wait to ensure it has dried out fully ??

 

[Richard C]

You must leave the screed to dry out thoroughly before you tile & at 1 day for every 1mm of depth, it could take longer than 4 weeks. You may be able to speed things up a little by having the UFH on low after,say, 3 weeks but if you tile too early or rush drying time it could end in tears. What type of screed is it, conventional sand/cement?

 

[UgsDIY]

I believe it was conventional screed, ordered from a local concrete delivery firm, I did have fibres added to it !!!
I have read somewhere that the drying time is 1 day per 2mm of screed ?

 

[Richard C]

Generally accepted practice & Building Regs requirement is 1 day per 1mm screed depth. This can be pushed a little as I advised but your other source is, maybe, being overly optimistic; even cement doesn’t fully chemically cure before 28 days. Your floor, your tiles, your choice!

 

[plstering]

id leav it 1mm per day and then use a good primer over the top

 

[UgsDIY]

Thanks both for your responses and i will be leaving it 1mm a day as recommended.
Plstering you brifely mentioned something about my next question, what I need to treat the new screed with before tiling, what type of primer do you recommend ??

Andy

 

[Richard C]

Use quality trade powder cement based adhesive not cheapo DIY crap & not tub mix. Before you go priming the screed, read & follow your chosen adhesive manufacturer’s instructions regarding priming. Sand/cement screed generally don’t need primer unless very dusty but Anhydrite screeds need an Acrylic primer.