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Tiling

Large format tiles over concrete / screed subfloor

Anonymous user 16/03/2024 - 2.37 PM

I have a large floor area (approx 60sqm) to tile (8-10mm porcelain tiles) that I want to lY large (90x90 or 120 x 120) tiles over. The subfloor is concrete with a 65-70mm screed over (with UFH - water piped). There is also an adjoining small area where the subfloor is green chipboard tongue & grooves over timber joists. The screed is sand and cement with fibres. The subfloor was laid about 8 months ago and the UFH has been used / commissioned and running for several months. My question is what is the best tiling prep needed? Do I need to use Ditramat over the concrete subfloor? And how much adhesive build up would I need? Thank you!!

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3 Answers

A1 ceramics ltd

Rating: 5 out of 5

Bideford

Grey area, depends on how well fixed the chipboard is. It needs screwing every 200mm if possible, and joists need to be sound. Belt and braces, backerboard chipboard and over board screed if you need to bring screed up to same level. Then ditra Matt whole area. Ideally you will still need to fit an expansion trim where timber meets screed. If chipboard is really stable just ditra whole floor but still use expansion joint or you run the risk of cracked tiles

Answered25 November 2020

Anonymous user

I’d recommend the dural matting system which can go right over the screed and chipboard. If you have a data sheet on what screed was used over your underfloor heating system that would be handy because tilers don’t receive this and there are certain practices that need to be carried out on different screed types. Also an 8mm notched trowel would be fine for the dural matting. The adhesive can be mixed quite wet for this you’d probably need 6-8 20kg bags of adhesive an S1 would be ideal. Make sure you sweep and prime before install and check if the new screed is anhydrite because if so the floor will need abrading. Hence why I mentioned the data sheet.

Answered7 November 2020

Anonymous user

Sorry, but I disagree with the previous answer of "if the chipboard is sound, Ditra the whole floor. Ditra and other forms of anti-fracture matting are for lateral movement and not deflection..... I do however agree with the rest of the previous answer.

Answered25 November 2020