Hi,

ive had a tiler tile my kitchen only to find after a week of being laid the tiles have lifted up, they havent taken to the floor (they sound hollow underneath), you can walk around the kitchen hearing them creek! i did mention to him before he started that it may need priming, but he said it would be ok. The house is a new build and the floor is a concrete screed flow floor finish. Should this have been primed by the tiler as a course of best practice, or is there another reason for this to have happened unrelated to the tiler, because it does need to be sorted and he's refusing to take the blame saying the screeders should have primed it.

Thanks in advance for your help.

hi matey.

On a fresh screed I always prime first, as they are nearly always dusty. If not primed then adhesive won't bond properly to screed. If not only to cover my own back.

Hollow sound may be a sign of spot fixing or it maybe that those particular tiles are loose already.

As for him saying that it should have already been primed? The people who lay the screed wernt to know what was going down. For example a carpet needs no primer so like I said it would have took tiler no time to prime, just in case.

Also find out what adhesive he used!

Sean

i agree with sean as above..also you had to mention to him you thought it may need primed to which his reply was it will be okay? he cant turn round now and say the guys who screeded the floor should have primed it,,primer costs pennies and takes no time to apply,also sounds like hes not properly fixed your tiles if they sound hhollow there is most probably air gaps underneath them,

Hi mate, what kind of tiles were they ?
Ceramic ?
Porcelain ?
Stone ?

He could have also used incorrect adhesive ?
That said it is always best to prime a new concrete floor

Hi,
Thanks for your prompt reply.
It is an Anhyrdrite screed floor not a concrete floor, sorry. The adhesive used is called Rapid set. The tiles were ceramic floor tiles. Is it always best practice to use a floor primer?

I always prime a screeded floor wether its new or old, it's just good practice. Just a thought, was the screed dry enough to tile onto. Moisture naturally comes to the surface during the drying out process making newly laid tiles seem to lift and sound hollow because you will get a certain amount of shrinkage in the screeed when it drys out. Hope this helps.

anhydrite screed needs special attention before tiling.
By the sound of things youv'e got trouble on your hands.

Yes it is isn't it............come on guys wake up


It's going to need taking up and re-laying I'm affraid

The surface of anhydrite screeds need scarifying to get off the latence (the light powdery surface), then seal twice in opposite directions before using a cement based adhesive to relay the tiles.

There is an easier way using a dry lay membrane, simply lay the membrane over the area and tile directly onto it...............easier but it costs more obviously.

Not sure this helps but your fixer needs a kick in the a$$

..

Agree with wetdec.....gypsum flow screeds like that needs propper preparation prior to tiling....and personally i would use a fexible adhesive as well....


How old is the flow screed..?

Trouble is that there will be numerous tilers who do not know what an anhydrite screed is. Therefore treat it as normal.

do they look different to concrete screed..

Yes often looks like self leveler with tiny bubble marks in it, light grey powdery colour feels matt to the touch ............

.

flow screeds need to have the top ground off with a diamond headed grinder then they need two coats of bal apd primer the adhesive will not stick to the flow screed it would be like tiling on a sponge it would suck the life out of the adhesive

Originally Posted by Leatherface

Trouble is that there will be numerous tilers who do not know what an anhydrite screed is. Therefore treat it as normal.

yeh well its their job to know leather , too many jokers about who think anybody can tile ..

hi guys

i have the same problem me 100m2 of classic travatine have also been laid on a gyvlon flow sreed floor by my tiler using a flexi rapid set adhesive we aloud the currect drying time and more, 1mm per day, my problem is that the floor was not primed before they were fitted and are now all coming loose after 6 weeks being down, i have come to terms with the fact they need to all come up and new ones relaid (my stairs and kitchen have been fitted on top of the tiles and i am hoping to take them up around them so with the adhesive already fixed on the back plus new adhsive the old ones i take up will be to proud when relaid) my problem is whos to blame, i told my tiler it was a screed flow floor and he asssumed that it was like any other concrete floor and that no primer would be needed,having read the previous posts i have gone back to the tiler saying it is good practice to prime first anyway and now he is trying to say he thought the floor had already been primed and that it was ready for him to tile on straight away, this is a mess, he is clearly trying to get out of this being his fault, i am a reasonable man and this sounds like an unfortunate mistake by a good tiler one that i have used many times before, he was not aware of the material that he was fixing too, i have not yet paid him for the work he has done, he is saying he will relay new ones free of charge and that i have to take up the old ones prime the floor and buy the new ones, is it me or does this sound like a bad deal if so can you tell me what a good one should sound like, i am trying to get a tilers perspective on this matter..

many thanks in advance

Hello and welcome...

You have stated that you informed the tiler that is was a flow screed floor, so in theory he should have known that you need to remove the laitence from the screed surface and then prime with acrylic primer twice...once in one direction then when dry prime in the opposite direction.

Did he ask you if the laitence had been removed and did he ask if a primer had been applied.....This to me just sounds like a case of lack of substrate preperation knowledge for flow screed and not his tiling skills ....So i think you need to put these options to him and then take it from there.

hi dave
thanks for the prompt response, thats exactly what it is....
he didnt ask if it had been primed as i told him it had not, he just didnt think it needed it.
any suggestions as to the best way forward

many thanks in advance

You need to confront him and tell him about removing the laitence and priming and that it was his mistake that he didn't know about the prep work for that type of substrate....he must hold his hands up that he didn't do it right....no costs should be incurred by yourself...imo..

Yes Anhydrite screeds always need sealing was water will cause a expansion within the screed a blow the tiles. You need a seperating barrier to tile sucsessfuly onto this type of screed

You seal gypsum based flow screeds to stop ettringite failure from using a cement based adhesive....

my understanding of ANHYDRITE SCREEDS is that they need scarifying by mechanical means and vacum up all loose chippings,apply two coats of primer (which is vital to ensure a bond between substrate and tile)AND USE RAPID SET FOR ADHESIVE UNLESS THERE IS UFH then a SPF should be used......is this not the correct way?

sorry just trying to get a better understanding of the substrate and how to deal with it...as i hav e no experience of working with Anhydrite screeds.

Some info that others might find useful........


Tiling On Anhydrite Screeds

While anhydrite screeds are growing in popularity throughout the UK, they are not without their critics, especially as a number of flooring installations over anhydrite screeds have failed. There are also many installations, of course, which have been completely successful. Like with fixing any flooring surface onto any type of substrate, long-lasting integrity can only be ensured by proper and adequate preparation.
While the Contract Flooring Association has published a technical paper on the generic installation of floor coverings onto these calcium sulfate-based screeds, Schlüter-Systems Ltd., is increasingly being asked about the specific requirements for a successful ceramic or stone installation on an anhydrite screed. And the tiling industry's trade body, The Tile Association, has also published a 21-page paper entitled "Tiling to Calcium Sulfate Based Screeds" which looks in detail at all considerations required for the perfect tiling installation.
As with all screeds, as long as appropriate steps are taken, there is no reason why tiled surfaces over anhydrite screeds cannot stay looking good for many years.
However, the choice of a ceramic or natural stone floor on anhydrite screeds needs careful consideration at the design stage - and contractors should consider bringing in tiling contractors who are familiar with fixing to calcium sulfate screeds, or, at the very least, seek advice from the tile manufacturers or suppliers - as, indeed, they should for all types of substrate.
One of the key considerations for a sound tiling installation on anhydrite screeds, is the preparation before tiling. The Tile Association recommends that where a calcium sulfate screed has been used - particularly where the finished floor may be exposed to moisture - a watertight membrane is installed.
According to the applicable standards, the residual moisture of such gypsum-based screeds should not exceed 0.5% prior to the tiles being installed. However, The Tile Association points out that with the use of a special separating - or uncoupling - system, tiling can commence on an anhydrite screed with a residual moisture content of 2% (by volume). It states: "One speciality separating system is a pressure stable polyethylene membrane, manufactured in a configuration that allows the tile adhesive to mechanically bond into the surface of the system. The separating function allows any stresses, such as drying shrinkage, that occur between the substrate and tiled surface, to be accommodated.
"Interconnected air channels on the underside of the separating system remain open allowing moisture from the substrate to evaporate, thus neutralising the vapour pressure in the calcium sulfate screed."
If required, the screed surface may need to be pretreated (sanding or priming) in accordance with industry standards and manufacturers' recommendations. A typical polyethylene membrane, as recommended by The Tile Association, is Schlüter-DITRA, which can be applied using a suitable adhesive that is suitable for the substrate.
It protects the screed against moisture penetration from the surface; especially important, as gypsum-based screeds are particularly sensitive to moisture and must be protected from additional moisture penetration.
Anhydrite screeds are a mixture of screeding sand and binder. If tilers are unsure of whether the screed they're to work on is, or isn't, anhydrite, they should always ask. Information about the screed should be kept in the building owner's Operation and Maintenance Manual.
MOVEMENT JOINTS
Provision should be made at the design stage for the thermal expansion of the screed and surface covering. Industry guidelines for ceramic and stone coverings require movement joints to be placed at all perimeters, and where tiling meets restraining surfaces such as steps, kerbs, columns and fixed plant etc.
Intermediate movement joints should be placed in accordance with the covering requirements, which, for ceramic tile and natural stone flooring is between 8-10 metres in each direction. Ideally the tile fields should be kept as square as possible.
Where underfloor heating is installed within the screed layer, movement joints should be used to divide the tile fields into areas of no more than 40 square metres, with the longest side no more than eight metres.
The movement joint should pass through the covering, adhesive bed and screed.
Movement joints should be placed in the screed in line with industry guidelines, however, because of the difficulty of forming such joints in the required precise location while the screed is being laid, it is advisable to form intermediate joints in non-heated screeds by using a dry cut floor saw to cut through the screed when the tiling is being installed.
The structural movement joints in the bed and tiling should be sited immediately over, and be continuous with, the joints in the base.
This is just a brief overview of what is needed for a successful ceramic or stone installation on an anhydrite screed.



So basicly if a gypsum screed is likely to get wet then a product like ditra should be used, but it is not likley to get soaked in a kitchen.....

Some other info as well.....


Tiling onto anhydrite screeds - Weber, world?s leading manufacturer of industrial mortars for the facade, tile fixing and construction markets

When a cement-based adhesive is applied directly onto the floor, cement in the tile adhesive reacts with the gypsum in the screed resulting in a mineral called ettringite being formed at the interface.

The associated structural change is sufficient to cause a complete debond of the cementitious adhesive away from the screed base.

As anhydrite cures, a weak layer of laitance is formed on the surface and should be removed.

This layer is too weak to tile onto and also slows the drying time of the screed.

Anhydrite screeds are made from inert fillers such as sand, with a binder system based on calcium sulphate. Consequently they can look very similar to a sand/cement screed.

Anhydrite will tend to appear lighter, sometimes almost white, but in practice it is difficult to identify an existing anhydrite screed from a traditional one.

brilliant technical info Dave.

http://www.ardex.co.uk/pdfs/ARDEX%20X7G%20PLUS.PDF

Calcium Sulfate based screeds i.e. Anhydrite
Ensure they have been laid and prepared in accordance
with the manufacturers recommendations. Generally
they require sanding and have a moisture content of
0.5% or less. Prime with ARDEX P 51, diluted with
3 parts of water.

Originally Posted by selfbuilder

hi guys

i have the same problem me 100m2 of classic travatine have also been laid on a gyvlon flow sreed floor by my tiler using a flexi rapid set adhesive we aloud the currect drying time and more, 1mm per day, my problem is that the floor was not primed before they were fitted and are now all coming loose after 6 weeks being down, i have come to terms with the fact they need to all come up and new ones relaid (my stairs and kitchen have been fitted on top of the tiles and i am hoping to take them up around them so with the adhesive already fixed on the back plus new adhsive the old ones i take up will be to proud when relaid) my problem is whos to blame, i told my tiler it was a screed flow floor and he asssumed that it was like any other concrete floor and that no primer would be needed,having read the previous posts i have gone back to the tiler saying it is good practice to prime first anyway and now he is trying to say he thought the floor had already been primed and that it was ready for him to tile on straight away, this is a mess, he is clearly trying to get out of this being his fault, i am a reasonable man and this sounds like an unfortunate mistake by a good tiler one that i have used many times before, he was not aware of the material that he was fixing too, i have not yet paid him for the work he has done, he is saying he will relay new ones free of charge and that i have to take up the old ones prime the floor and buy the new ones, is it me or does this sound like a bad deal if so can you tell me what a good one should sound like, i am trying to get a tilers perspective on this matter..

many thanks in advance

All screeds should be primed prior to fixing tiles. Anhydrite is no exception.Indeed it has a very absorbant surface so will as one previous poster said "suck the life out of the adhesive. If the screed has a laitance this should be sanded off and the dust removed to leave a clean dry dust free surface. If a cement tile adhesive is to be used then I would suggest a water based epoxy primer or at least 2 to 3 coats of good quality acrylic. This should be one that does not reqire diluting IMO. the epoxy will prevent the migration of sulphates through the primer thus preventing ettrignite reaction. Alternatively you could use a gypsu based tile adhesive although there are not many of these about in the UK yet. . there are several of these in France where much more anhydrite is used.