Do I need an uncoupling membrane?

[Stevoe]

Wow Ajax123, very comprehensive, clear and unambiguous, thank you. I have had great difficulty in getting anhydrite screed in Lincolnshire, the only company that I could find did not want to supply it as my builder is not an registered liquid screeder (they said it was a government requirement?) and probably because I am doing it myself too. So I consulting Nu-Heat (UFH supplier) they agreed that it would not make much difference to put a normal cement screed down though the liquid would be better, so the concrete supplyer is supplying normal screed (stuff with fibres in) the UFH supplier said I should use a minimum of 65mm too and that is achievable, the UFH pipes rest in clip-tracks that are stuck down, there are some staple type clips too but not that many, they do puncture the dpm that I placed ontop of the insulation but sit flush. The kitchen was a garage so the concrete there is 15 years old, we know there is dpm and insulation already, I have put further insulation and a further dpm before the cliptracks and pipes, I will have to take the risk of tiles popping the risk seems slight from what you have said. The other three areas are newly concreted (December '08), there is a dpm 1200g Visqueen beneath the concrete, again I am going to have to take the risk of moisture entrapment and because the risk is slight and because everything is ready, the screed arrives thursday, there is no time for re-work.

After your observations maybe the Topps chap was looking at the Homelux as a vapour barrier more than a decoupler, he showed me a cardboard box lined with Homelux filled with water (even had a duck in it) to show how good it was.

Excuse my ignorance but what is "addy" I assume it is a term for adhesive/cement and does this mean I have to prime the screed too. If so my understanding is that I need to prime, then flexible cement (I have Ultra Pro-Flex SP for one of the areas supplied with the tiles) then matting, flexible cement then tile and grout. This would be after the screed is dry and the comissioning process has been completed of course.

 

[Ajax123]

I have had great difficulty in getting anhydrite screed in Lincolnshire, the only company that I could find did not want to supply it as my builder is not an registered liquid screeder (they said it was a government requirement?)
After your observations maybe the Topps chap was looking at the Homelux as a vapour barrier more than a decoupler, he showed me a cardboard box lined with Homelux filled with water (even had a duck in it) to show how good it was.

Excuse my ignorance but what is "addy" I assume it is a term for adhesive/cement and does this mean I have to prime the screed too. If so my understanding is that I need to prime, then flexible cement (I have Ultra Pro-Flex SP for one of the areas supplied with the tiles) then matting, flexible cement then tile and grout. This would be after the screed is dry and the comissioning process has been completed of course.

It sounds to me like you have been given quite a bit of bull**it on this one. If you will forgive the term of phrase
There is no such thing as a "government requirement" that you have to be a registered installer with anhydrite. That is complete and utter nonsense. If you need some contacts for installers in your area I will be very pleased to talk to you. Send me a private message or ring me at work on 07545 932723. Lincoln is not over run with installers but there are plenty about and they are as desperate for work as tilers at present so am sure would be grateful for the lead. Also the more established screeders tend to travel. I know of 2 in Lincoln, 1 in Boston, one in Scunthorpe, several in Nottingham and Mansfield so there is no shortage.

Obviously if you cannot turn back from sand cement then the decision is made but obviously for future reference.....

Anhydrite is available from Tarmac as Truflow and from Lafarge as Agilia Gyvlon. It is true to say that they will only sell it to people who have been on a training course at present (which incidentally I run) as it is important that the people that install these things know what they should be doing. It is equally fair to say however that they are both resonably comfortable in training anyone who is interested although they always have to balance demand and numbers and also have to take into account the cost versus benefit. If you are doing this as a one off I would think you would be better to use a previously trained installer anyway. You don't want it as a practice ground. Lafarge run an approved user scheme specifically for builders and developers who do not wish to go outside of their business to sub contract. It would be unusual for a self builder to take this on themself but it is by no means unheard of and some have actually gone into business as a result of training.

65mm sand cement on insulation and underflor heating will crack so you need tom make sure you joint it adequately to control the cracking. The advice of the NHBC is that is should be split into 15m2 bays or room size whichever is smaller with an aspect ratio no more than 2:1. There should be full thickness isolation joints across door thresholds and between areas of differential temperature e.g. if your lounge is split into two separately controlled heating zones it needs a joint or if you have a conservatory you will need to separate it from the lounge because of the level of thermal gain. Finally you need joints at areas where there are large changes to aspect ratio e.g. if you have large room that is semi split with a double door, or if you have a L shaped room there should be a joint. All of these joints are best placed into the screed during installation as they should be full depth and filled with compressible material such as etherfoam. They would normally need to be between 5 and 12mm wide. All joints should relfect through your tiled surface even if you use a decoupling mat. You can use the decoupling mat as a waterproofing barrier but any joints should be sealed (in the case of Ditra with a Kerdi Strip joint) It will also need to be reinforced. You will probably be best served using polyproylene fibres for this as the distribution through the mix is better than with d49 mesh. The fibres will usually be added at the batching plant for readymixed screeds.

I am obviously sorry you have been unable to use flowing on this one but hopefully if there is a next time you will consider it again.

Oh by the way - addy - short for adhesive. You will need to prime the surface of the screed before applying flexible adhesive. A good quality acrylic primer will be fine (not PVA) you then lay the matting and then tile on top of it again with flexible adhesive. Schluter have a video on their website of their stuff being laid if it is any help

 

[Stevoe]

Ajax123,

Many thanks for all of that very valuable information, the screed is bought and paid for through the suppliers now and the workforce is prepped and waiting, so I really don't want to stop that snowball, I do wish I had sought advice earlier as the self levelling stuff just seems to make more sense but as my very astute wife tells me "prior planning prevents pi*s poor performance" and it look as if I will hearing that again.:mad2:

I will take a little extra time and seek advice from the forum for the walk in shower (next project) but until then we are limbering up for a day of hard graft screeding.

Regards

 

[Ajax123]

Ajax123,

Many thanks for all of that very valuable information, the screed is bought and paid for through the suppliers now and the workforce is prepped and waiting, so I really don't want to stop that snowball, I do wish I had sought advice earlier as the self levelling stuff just seems to make more sense but as my very astute wife tells me "prior planning prevents pi*s poor performance" and it look as if I will hearing that again.:mad2:

I will take a little extra time and seek advice from the forum for the walk in shower (next project) but until then we are limbering up for a day of hard graft screeding.

Regards

Best of luck. Perhaps some pics posted of the finished job might be nice

 

[DHTiling]

The homelux mat is simply a tanking / anti fracture membrane and NOT an uncoupling membrane.

 

[Ajax123]

The homelux mat is simply a tanking / anti fracture membrane and NOT an uncoupling membrane.

presumably equivalent to Schluter Kerdi system then?

 

[DHTiling]

YEP!! but thicker....:smilewinkgrin: and with bonny pictures on it...

 

[Stevoe]

Looks like Dura or Ditra then, tried to contact Tony at Tile Kings for the Durabase but no pickup on the phones and no response from an earlier email, have a couple of weeks+ at least yet though so will hold out, will post pictures if I can get my head around it. Huge thanks to all who have contributed to my querrie, I am sure similar questions have been posted before and I aplaud the indulgence you have afforded me.

 

[DHTiling]

Looks like Dura or Ditra then, tried to contact Tony at Tile Kings for the Durabase but no pickup on the phones and no response from an earlier email, have a couple of weeks+ at least yet though so will hold out, will post pictures if I can get my head around it. Huge thanks to all who have contributed to my querrie, I am sure similar questions have been posted before and I aplaud the indulgence you have afforded me.

WHO??..

try here>>> Wetdecs wet room supplier, wet room shower tray, tanking. waterproofing from leading wetroom company.

 

[Stevoe]

Sorry it was Tony at Wetdecs not Tile Kings, took the link from the Forum my mistake for the Faux Pa