Expansion Joints

[AD Ceramics]

Hi all

I am installing a 600x600 limestone tile to a kitchen floor on a sand and cement screed with wet underfloor heating system, laid on Ditra Matting, Mapei Keraquick adhesive with Ultra colour grout, the floor is approx 70m² 11x6.5m.
The sand and cement screed was laid in one hit with no dry joints other than across a couple of doorways which the tiling finishes.
I was questioned by the QS the other day whilst at a site meeting as to why I haven't installed an expansion joint in the floor, my reply was that there is no expansion in any part of the floor whether it be the screed or the block and beam floor below that and the customer would blow a fuse if I installed a mechanical expansion joint in her very expensive kitchen floor.
Seriously understand the need for expansion joints but I am pretty confident that the floor will stand up to the stresses and strains as I have done a couple of similar size with the same spec previously and had no problems.
I was just wondering if any of you guys have similar experiences or had problems or views on my thoughts.

Kind regards

Paul

 

[philipb]

Hi Paul,
Expansion joints are normaly put in on runs of 10 m or more,if i was you
i would loose the ditra and the addy you have chosen.
Granfix do a addy that goes onto the screed with no decoupling.
Used it twice now with no problems,saved a fortune in materials and labour.
Talk to granfix tech,they will help you,they even supply a additive
that mixes with the grout,makes it like bubble gum.
They will also advise on the comisioning the floor with this process.

 

[Ajax123]

Hi Paul,
Expansion joints are normaly put in on runs of 10 m or more,if i was you
i would loose the ditra and the addy you have chosen.
Granfix do a addy that goes onto the screed with no decoupling.
Used it twice now with no problems,saved a fortune in materials and labour.
Talk to granfix tech,they will help you,they even supply a additive
that mixes with the grout,makes it like bubble gum.
They will also advise on the comisioning the floor with this process.

Sorry Philipb but that is poor advice. The British standard 5385 part 3 states quite categorically that natural stone on heated screed needs to be uncoupled. The fact that the screed at 70m2 with embedded underfloor heating has no joints in it means it is a high risk floor. Heated sand cement should be split into bays of 15m2 or room size to be done correctly (NHbC chapter 8). If you choose to ignore the standards that are written by panels of experts and you get away with it that's fine but if it goes wrong you would not have a leg to stand on in court. Can you really see gran fix standing up in court defending you... I think not. If it were ceramic or porcelaine on a correctly laid and configured screed the I would agree no ditra. But limestone on a heated and incorrectly laid screed... I don't think so.

bear in mind also that the pints are not just for expansion but for movement in all directions. Expansion is only one aspect. Long term shrinkage of the screed is likely to have more of an effect and will take the limestone with it If the screed cracks.

 

[Stef]

I have just spent 3 days ripping up 38 limestone tiles (600x400) on a heated screed.
We laid them almost 2 years ago & advised the builder it had to be uncoupled but they wouldn't listen.
This job will end up costing them more in the long run..
Listen to Alan (Ajax) on this one, he's yr man.

 

[AD Ceramics]

Sorry Philipb but that is poor advice. The British standard 5385 part 3 states quite categorically that natural stone on heated screed needs to be uncoupled. The fact that the screed at 70m2 with embedded underfloor heating has no joints in it means it is a high risk floor. Heated sand cement should be split into bays of 15m2 or room size to be done correctly (NHbC chapter 8). If you choose to ignore the standards that are written by panels of experts and you get away with it that's fine but if it goes wrong you would not have a leg to stand on in court. Can you really see gran fix standing up in court defending you... I think not. If it were ceramic or porcelaine on a correctly laid and configured screed the I would agree no ditra. But limestone on a heated and incorrectly laid screed... I don't think so.

bear in mind also that the pints are not just for expansion but for movement in all directions. Expansion is only one aspect. Long term shrinkage of the screed is likely to have more of an effect and will take the limestone with it If the screed cracks.

Hi Ajax

I do understand what you are saying, but to ask the contractor I sub-contract for to install 15m² bays in the screed would be impossible, I try to put breaks across all doorway as this seems to be a weak point for the screed cracking but as for a main area no chance, I install Ditra under every tile I install for them even if there is no heating as most of the time the screed is fairly green(and I don't pay for it they do)
So if there was a bathroom with 25m² would you expect to see a movement joint Ajax? not many of the rooms in these houses I do have floor areas much smaller than that unless it is a smaller ensuite.
Been a member of this site for a while but never got around to making a post, it'll be great to bounce ideas about and questions on here, it's rare I meet up with other tilers on site.

Cheers lads.

 

[Ajax123]

Hi Ajax

I do understand what you are saying, but to ask the contractor I sub-contract for to install 15m² bays in the screed would be impossible, I try to put breaks across all doorway as this seems to be a weak point for the screed cracking but as for a main area no chance, I install Ditra under every tile I install for them even if there is no heating as most of the time the screed is fairly green(and I don't pay for it they do)
So if there was a bathroom with 25m² would you expect to see a movement joint Ajax? not many of the rooms in these houses I do have floor areas much smaller than that unless it is a smaller ensuite.
Been a member of this site for a while but never got around to making a post, it'll be great to bounce ideas about and questions on here, it's rare I meet up with other tilers on site.

Cheers lads.

in a bathroom of 25m2 with underfloor heating I would have to advise placement of a joint but of course being pragmatic in I would not expect to see it placed. The incorrect installation of screeds has been going on for years . The simple fact is though I have you advise best practice and not what you would generally get away with.

There is an old saying that suggests that rules are for the obedience of fools and the guidance of wise men. The rules for laying screeds I.e. The relevant British standards 8204 parts 1 to 7 are written by committees of experts drawn from diverse fields within the screeding industry. The standards lay down rules to make the design and installation of screeds robust including guidance on joints. I guess My own technical knowledge of screeds and the interactions between interfacing materials allows me to make and educated judgement as to the realistic need for joints in any given situation. Many screeders know how to lay a screed but don't necessarily know about what happens within a screed in different circumstances so would be wise to cover themselves by sticking to the rules.

If a screed is not laid correctly then it isprobably even more critical that the tiler mitigates his own risk by incorporating mechanisms such as ditra to help reduce his own exposure to the risk left behind by the preceding trade.

 

[AD Ceramics]

You're a wise man Ajax....... A wise man


Thank you:hurray:

 

[DHTiling]

This info is the bs5385 tiling to heated screeds.

Movement joints in the floor tiling onto heated screeds should be incorporated as outlined in British Standard BS 5385: Part 3:1989 Clauses 19 and 23.6 and BS 5385 Part 4. Briefly, this document requires that joints be located over existing and/or structural movement joints. Around the perimeter of the floor and where tiling abuts columns, curbs, steps and plant fixed to the base. In large floor areas tiles should be divided into bays not exceeding 25 square metres in area.


The problem is in domestic installations , is aesthetically it can spoil the look.

 

[m3fitter]

Guys. On the subject of decoupling underfloor heated floors, I am increasingly getting developers question the use of ditra on screed, obviously, I don't want to lose their business but do need to direct them to an authority or type that states it, where can I link them to for them to read about it, I have personally seen porcelain after 6 years crack on ufh screed, so I don't need convincing...its them..

Ps Granfix are pants

 

[Ajax123]

Guys. On the subject of decoupling underfloor heated floors, I am increasingly getting developers question the use of ditra on screed, obviously, I don't want to lose their business but do need to direct them to an authority or type that states it, where can I link them to for them to read about it, I have personally seen porcelain after 6 years crack on ufh screed, so I don't need convincing...its them..

Ps Granfix are pants

How about directing them to bs5385. One of the issues might be the recomendation for ditra in situations where it isn't needed. And of course the cost....

 

[m3fitter]

Found this on schluter website: Successful installation over floor heating systems using an uncoupling membrane - Schluter-Systems


Precaution should be taken when installing ceramic tile and natural stone over heated substrates. The effect of temperature fluctuations during the heating and cooling processes induces thermal movement that without proper compensations will lead to failure in the surface covering. Applying an uncoupling membrane has proven to be a successful technique for a variety of floor heating systems
An uncoupling membrane serves several functions in successful tile installations and is particularly suitable for floor heating systems.
The membrane uncouples the tile covering from the substrate and prevents the transfer of stresses to the tile flooring. As a result, stresses caused by deformation of the substrate through thermal movement, shrinkage of the curing screed or concrete, deflection, etc. are neutralized.

 

[Ajax123]

Found this on schluter website: Successful installation over floor heating systems using an uncoupling membrane - Schluter-Systems


Precaution should be taken when installing ceramic tile and natural stone over heated substrates. The effect of temperature fluctuations during the heating and cooling processes induces thermal movement that without proper compensations will lead to failure in the surface covering. Applying an uncoupling membrane has proven to be a successful technique for a variety of floor heating systems
An uncoupling membrane serves several functions in successful tile installations and is particularly suitable for floor heating systems.
The membrane uncouples the tile covering from the substrate and prevents the transfer of stresses to the tile flooring. As a result, stresses caused by deformation of the substrate through thermal movement, shrinkage of the curing screed or concrete, deflection, etc. are neutralized.

but
suchluter don't write the standards, they sell ditra. Not saying it is not of benefit. Clearly it can be but as per my pm it is not always necessary.

 

[Ajax123]

No reason for it to be private so have put it in the public thread hope that's ok with you m3fitter

q. Are you saying that Ditra isn't recommended on screed with UFH ???



A. not in all cases. The British standard only make reference to the need for uncoupling natural stone tiles. This recomendation is reflected by the British stone federation. Even then neither say that uncoupling should be by means of an uncoupling membrane such as ditra. Uncoupling can be achieved by other means. Realistically the ditra type systems are the modern way to acheive uncoupling.


The success or failure of any floor also depends on the quality of the substrate. If the screed is laid correctly and the tiles are laid correctly with appropriate joints etc etc, then it is arguable and indeed likely that uncoupling would not be needed with any tile type, except the natural stone caveat.


all that said if you can get the dosh for it then it is not likely to do any harm so go for it...

 

[m3fitter]

of course, I understand, but as a tiler, trying to alleviate problems and keep a good relationship with developers that use you year in, year out, I have to advise them of the fact that decoupling, can only benefit them, especially on large areas, if the screed hasn't been installed with movement joints

 

[Ajax123]

of course, I understand, but as a tiler, trying to alleviate problems and keep a good relationship with developers that use you year in, year out, I have to advise them of the fact that decoupling, can only benefit them, especially on large areas, if the screed hasn't been installed with movement joints

Ill agree with that. Seems sensible.