are expansion joints in tiling pointless if there is no expansion joint in the screed ?

[Samb213]

hey all just got a job that requires me to tile 150m2 floor using porcelain wood effect plank tiles

the main area ill be tiling is around about 100 m2 with the other 50m2 spread over the house in hallways..bathrooms etc

the thing is the main area ill be tiling (100m2) is a power floated concrete floor with a pipes and water heating system fitted ...looking at the floor theirs no expansion joints fitted in the screed at all apart from around the perimeter

from what ive been told expansion joints incorporated into your tiling are kind of useless if the expansion joint doesnt follow through into the screed its self

how would everyone go about tiling this floor

would you still bother incorporating expansion joints into the tiling even though the screed doesnt have any ?

my other option is to use ditra matting which would cost the customer a fair bit but i guess then my back would be covered

anyway just thought id try getting a few opinions on this before i crack on with it

 

[hmtiling]

Ditra won't remove need for an expansion joint. You'll only need one which could be be done with colour coded silicone and not look awful Imo. Power floating the floor was not wise. I'd be using tilemaster prime plus grip or similar. Expansion round the perimeter is crucial.

 

[Samb213]

cheers for the reply ...yeah all the skirtings are coming off so it will have a good 10mm expansion around the perimeter . .so you think I'll get away with just one silicone expansion joint running horizontal across the center of the room then ?.obviously I won't get away with running any expansion vertically on the floor with it been planks laid in a running length pattern..well without cutting it into the tiles which I doubt the customer would go for anyways

 

[Samb213]

would you still bother with the ditra then to be on the safe side or do you think a good flexible adhesive plus a couple of expansion joints should be enough to cover any movement in the screed ?

just been quoted a ridiculous price on 150 meters of ditra so I'd rather avoid it if I can

 

[hmtiling]

I'd be happy to tile without ditra. The thin decouplers can be a lot cheaper so worth having a look.

 

[Rich Midge]

I'd go with a decoupler I think. TM antifracture mat and silicone the perimeter and the doorways.

 

[Rizzle from the Portizzle]

dont forget to cut 6mm back from all door frames on heated screeds .also each grout joint is an expansion joint so
on planks you will have loads of expansion joints

 

[Ajax123]

in direct answer to your question there are 2 reasons why expansion joints in the tile face are required even if there are no joints in the screed. firstly though the British standard for screeds says that for sand cement they should be split into bays approximately 40m2. If this is not done and you tile it technically you would be acting without due diligence so could be held liable if there is a problem later unless you have demonstrated that you don't need the joints in the screed e.g. with anhydrite.

Now for the reasons. If you are happy that no joints are needed in the screed and do not put joints in the tiles you will not have followed the British standard for tiling which sets out joint spacing. Again if this causes an issue later on e.g. restraint cracking or bellying then you could be held liable as you will not have observed Due diligence

the second reason is that the screed and the tiles may expand and contract at different rates and to different extents. again with reference to anhydrite this is more dimensionally stable than cement based screed so requires fewer joints. the rate at which the tiles will expand will be greater than that of the screed. As the tile face and the screed do not act in a truly composite manner due to the flexibility of the adhesive undue stress will be placed on the adhesive/screed interface and the tiles will pop off. so you need to relieve this stress by incorporating joints in the tile face.

there you are... clear as mud

 

[One Day]

Use Ditra. Sleep well!

 

[Dumbo]

would you still bother with the ditra then to be on the safe side or do you think a good flexible adhesive plus a couple of expansion joints should be enough to cover any movement in the screed ?

just been quoted a ridiculous price on 150 meters of ditra so I'd rather avoid it if I can

Buy dural ci matting direct from dural . Cheap as chips . I have used loads of it never had a problem apart from wanting to curl at end of roll so just put some at end of run . Also Hampshire tile warehouse normally do good deals on full rolls of Ditra. But it would have to get to you might be worth a call .