Cement board over anhydrite screed

[faceman]

We have a floor to do which has ended up being way to low. We to bring the whole floor up about 14mm before we mat it and tile it. It is 180m in a very old expensive house that has original skirts and stair cases still in place that we need to get up to. We figured a 12.5mm cement board would be the quickest way. There is very little information about fitting cement boards over anhydrite(why would you?) and I would appreciate any smart advice. UFH is in the screed so screwing is out of the question. I appreciate this could throw up all sorts of issues.

 

[hmtiling]

Anhylevel from tile master
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Think uzin and some other flooring companies do gypsum based levellers too

 

[Ajax123]

Put 15mm of ts-15 screed on top on a polythene membrane

 

[Huddersfield Tiling]

We have a floor to do which has ended up being way to low. We to bring the whole floor up about 14mm before we mat it and tile it. It is 180m in a very old expensive house that has original skirts and stair cases still in place that we need to get up to. We figured a 12.5mm cement board would be the quickest way. There is very little information about fitting cement boards over anhydrite(why would you?) and I would appreciate any smart advice. UFH is in the screed so screwing is out of the question. I appreciate this could throw up all sorts of issues.

Apply another top screed is the only way. Boarding over with a cement board will create a major heat barrier from the existent UFH. I'm afraid you'll have to pay up to save.

 

[hmtiling]

Apply another top screed is the only way. Boarding over with a cement board will create a major heat barrier from the existent UFH. I'm afraid you'll have to pay up to save.

Not really. The cement board will act as thermal mass just like screed does

 

[Ajax123]

Not really. The cement board will act as thermal mass just like screed does

Not strictly true mate. Every time you introduce a new layer you introduce a barrier due to the different specific heats of the different layers and the air trapped between the layers. That's said I dont thinking would present a "massive" barrier to heat and is a realistic solution if done properly. I still prefer screed kn screed though with 15mm of TS15.

 

[hmtiling]

Not strictly true mate. Every time you introduce a new layer you introduce a barrier due to the different specific heats of the different layers and the air trapped between the layers. That's said I dont thinking would present a "massive" barrier to heat and is a realistic solution if done properly. I still prefer screed kn screed though with 15mm of TS15.

If fitted properly shouldn't be any air in between.
By that logic the same would apply to a layer of slc?
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Not strictly true mate. Every time you introduce a new layer you introduce a barrier due to the different specific heats of the different layers and the air trapped between the layers. That's said I dont thinking would present a "massive" barrier to heat and is a realistic solution if done properly. I still prefer screed kn screed though with 15mm of TS15.

Just read up on that ts15. Definitely the way to go here

 

[Glynn]

Could always us Tilemaster Adhesive's Anhylevel