Ufh with conventional screed

[Turkish tiler]

What is you view on conventional screed use with piped underfloor heating ??

 

[Chalker]

For tiling purposes, as long as it's nice and flat there's no problem. Best with added fibres.
but liquid screed is better for a " plumbing" point of view. The liquid types of screen encapsulate the ufh pipework better than conventional screed. This helps the floor to heat up better.

 

[nybor62]

nice and flat is the WORD , ive always ended up having to latex them . seems to be a shortage of good screeders
the guy i do quite a lot of work for insists on using is own screeders , i reckon they must be cheap , there hopeless

 

[Ajax123]

Traditional sand cement screed with warm water underfloor heating is pretty rubbish from the point of view of the heating. It is also prone to shrinkage and cracking. deffinitely requires poly fibres or D49 steel mesh reinforcement. UFH must be comisioned and run prior to tiling and this should not be done for at least 28 days following installation. (7 days curing under polythene followed by 21 days of strength gain)

the only thing it really ha going for it is the fact that cement based adhesives stick to it. I know it is obvious that I would say go for liquid screed everytime but I would go for liquid screed everytime.

 

[Andy Allen]

Every s/c heated screed I look at seems to have cracks all over them...

 

[Turkish tiler]

Reason I asked question. Last two years I have took out three floor with piped underfloor heating, screeds were sand and cement two of them with fibre. All three screed had thermal damaged, turned in to sand (baked) And tiles were loose
any of you come across this?

 

[White Room]

Sounds like there've been banging the heating far to soon not allowing any curing time and the moisture is released....

 

[Chalker]

I'm with above. Heating turned on and up too soon. Or running floor temp too high. There are yo many plumbers fitting ufh at a general rule of 200mm centres. Hoping for the best and just turning the water temp up.

 

[Turkish tiler]

I don't think conventional screed even with fibres is not suitable for ufh

 

[White Room]

I think Ajax would probably agree to that....

 

[Ajax123]

I think Ajax would probably agree to that....

Not so much that it is not suitable. That would be unfair as it has been used for years in many cases successfully. There are a number of issues though. Installations are often poor due to the lack of skills in the industry, designs are often defficient and movmenet is uncontrolled. Sand cement is often not sured leading to shrinkage and dusting and a lack of strength. They are often installed far too dry leading to poor compaction and poor strength gain. lost of issues and the even following the british standards for sand cement does not help as 8204:1 says its better to lay big bays let them crack and sort it out afterwards. This seems mad to me... Then there is 1264, The heating standard, which is dangerously wrong when it comes to comissioning the heating system.

Anhydrite screeds are technically superior to sand cement and when it comes to underfloor heating it is perfectly suited to modern construction methods and buildig regulations.

That is not to say it never goes wrong. Occasionally it does.but is is much less prone to failure when installed correctly.

 

[Donnie Ban]

4 years ago my wife and I put down insulation, laid the pipes and did all the heating including the wiring of the manifold and programmable roomstat in each room, with help we DIY mixed 4 to 1 crusher dust or quarry dust with loose glass fibres, bought a cheap electric vibrating poker on ebay, that meant the screed seeped under the pipes as there where no stones. I did 5 rooms individually, 1 lounge 1 bedroom 1 bathroom 1 kitchen 1 u/t and toilet. I then covered each room individually with tarpaulins so the cement would cure instead of dry, left them for the recommended weeks plus an extra week, tiled them, put heating on as recommended and 4 years later as there is not a crack to be seen anywhere. I am only a diyer and never tackled anything like this before, so if you think you can do it give it a go, but make sure you read up on it first

 

[Ajax123]

4 years ago my wife and I put down insulation, laid the pipes and did all the heating including the wiring of the manifold and programmable roomstat in each room, with help we DIY mixed 4 to 1 crusher dust or quarry dust with loose glass fibres, bought a cheap electric vibrating poker on ebay, that meant the screed seeped under the pipes as there where no stones. I did 5 rooms individually, 1 lounge 1 bedroom 1 bathroom 1 kitchen 1 u/t and toilet. I then covered each room individually with tarpaulins so the cement would cure instead of dry, left them for the recommended weeks plus an extra week, tiled them, put heating on as recommended and 4 years later as there is not a crack to be seen anywhere. I am only a diyer and never tackled anything like this before, so if you think you can do it give it a go, but make sure you read up on it first

blimey what a flipping faff...