Hello everyone, we want to have our bathroom tiled as part of a renovation. It is located on a wooden joist ceiling.
Dry screed was installed here, and the tiler came for an inspection and tested the subfloor (he jumped on it a bit, etc.) and said it was no problem, that tiles can be laid with a decoupling membrane.
I’m not completely sure and mentioned that I could do some additional work before the tiling begins. He said that wouldn’t be necessary.
That’s fine with me for now. But if in the worst case the grout cracks or something similar happens after a year – would a warranty apply and would I have the right to have the tiler come back and fix it?
In my research, I’ve only found conflicting information...
Dry screed was installed here, and the tiler came for an inspection and tested the subfloor (he jumped on it a bit, etc.) and said it was no problem, that tiles can be laid with a decoupling membrane.
I’m not completely sure and mentioned that I could do some additional work before the tiling begins. He said that wouldn’t be necessary.
That’s fine with me for now. But if in the worst case the grout cracks or something similar happens after a year – would a warranty apply and would I have the right to have the tiler come back and fix it?
In my research, I’ve only found conflicting information...
KlaRa schrieb:
In my view, the discussions keep drifting further away from the original question of the person who asked.
Fundamentally the following applies:
In bathrooms, especially in timber-framed buildings, the floors must be sealed so that in the event of an incident no water can seep underneath the floor construction. Just imagine the damage that would result if water were to flow down the wall surfaces into the lower levels of the building.
Now, as the questioner explained, we have a walking surface made of gypsum fiber panels. The inspection and duty of care of the floor installer (in this case: the tile installer) therefore specifically relates to a substructure that significantly differs from a conventional mineral screed.
Such a construction must certainly be checked sufficiently and appropriately for possible deflections under point loads.
Ultimately, in the event of damage, proof must be provided of which inspections were carried out according to which methods—and which results were apparent at the time.
Later simply stating "Everything was fine" will certainly not serve as an exonerating argument for the tile installer in case of dispute.
In the simplest case, a long straightedge is placed on the unloaded surface of the dry screed elements, and the surface is then loaded with body weight. There must not be any significant deflection.
However, since there will inevitably be deflections, especially with a timber joist ceiling, the manufacturers of the lightweight construction specify a maximum tile size of 30cm x 30cm (12" x 12") along with a flexible adhesive and flexible grout joint.
That covers ceramic floor coverings.
Now let’s turn to the preparatory work.
This consists of waterproofing the entire bathroom surface, regardless of the water exposure class, using a suitable liquid waterproofing membrane.
Anyone thinking of using a bituminous sealant at this point should quietly reconsider and follow the further discussion on this topic passively.
A bitumen-based waterproofing membrane indoors, especially on gypsum fiber boards (prefabricated screed), is a no-go!
Once the floor surface has been coated with the first waterproofing layer, the transitions on rising surfaces are integrated into the second liquid waterproofing layer within around 12 hours using appropriate sealing tapes and system corner solutions. This second layer usually has a different color than the first layer so that any missed spots can be quickly identified.
An uncoupling mat usually serves only the craftsman, as they tend to pass on the associated costs to the often anxious and solution-grateful client.
It should at least be briefly noted here that uncoupling mats are only used for critical screeds.
A floor level based on (naturally suitable) gypsum fiberboard is not a critical substrate!
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To summarize:
Waterproofing, for example based on a brush- or roller-applied liquid membrane, combined with sealing tapes on rising wall surfaces, is absolutely essential in timber frame construction.
An uncoupling mat is by no means a required building material when new gypsum fiberboards are used as “dry screed.”
Flexible auxiliary construction materials such as flexible tile adhesive and flexible grout are also necessary.
Tiles must not exceed 30cm x 30cm (12" x 12"), otherwise, due to the unavoidable deflections of dry screeds on timber joist ceilings, there is a significant risk of breakage or cracking from normal use loads.
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I hope these notes are helpful once again!
Regards, KlaRa Thank you very much for this detailed and especially question-related answer!
A primer was applied over the dry screed panels, then the uncoupling mat was bonded with flexible mortar. The inside and outside corners, as well as the entire wall surfaces, were sealed with a blue waterproofing tape. So everything is in order. The connection to the shower tray was also done properly.
My concern is only about the deflection of the substrate. There were sometimes about 2-3mm (0.08-0.12 inches) of deflection. I pointed this out to the tile installer. His response was: Everything is fine. The flexible adhesive adds so much stability to the substrate that it is not an issue.
The tile size is now (unfortunately) 60cm x 60cm (24" x 24"), laid with 5-8mm (0.2-0.3 inches) of flexible adhesive and grouted with flexible grout.
And I have my doubts whether this will be durable (which I also expressed earlier). Hopefully, time will tell.
My real concern, in case it doesn’t hold up, was whether I have any claims or recourse.
Finch039 schrieb:
In a worst-case scenario, I just wanted to know if I have any claims if it doesn’t hold up. The answer to this question is simple:
If it was an official contract (not just “neighborly help,” as it’s often called), then according to building regulations, you have a warranty period of 5 years.
I would recommend keeping the final invoice as well as—if available—the craftsman’s original quote, plus any dated notes or comments regarding concerns!
The flexible adhesive is not related to the risk of ceramic tiles breaking in larger formats!
The crucial factor here is the deflection of the substrate, as these stresses affect the tile material structure.
If the bending tensile stresses caused by substrate deflection exceed the inherent strength of the tiles, the flexible adhesive won’t save them.
I don’t want to be “doom and gloom” here!
Even if workmanship in some cases doesn’t fully meet current standards, that doesn’t necessarily lead to damage.
That’s exactly why the client has a warranty on materials and services.
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Regards, KlaRa
KlaRa schrieb:
The answer to this question is simple:
If it was an official contract (not just “helping out the neighbor,” as it’s called), then according to building regulations, you have a warranty period of 5 years.
I would recommend keeping the final invoice, as well as—if available—the craftsman’s original offer and any dated notes regarding concerns very carefully!!
The flexible adhesive has nothing to do with the risk of breakage in larger format ceramic tiles!
The deflection of the substrate is the crucial factor here, as these stresses affect the tile material structure.
If the bending tensile stresses caused by substrate deflections exceed the intrinsic strength of the tiles, the flexible adhesive will not save them.
I do not want to “paint the devil on the wall” here!
Even if workmanship in some cases does not meet the current technical standards, this does not necessarily lead to damage.
That is exactly what the builder’s warranty for materials and services is for.
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Regards, KlaRa Official contract with invoice. Thank you very much for your help 🙂
Finch039 schrieb:
The tile size is now (unfortunately) 60 x 60 cm (24 x 24 inches) Finch039 schrieb:
And I have my doubts whether this will hold up in the long run (which I had already mentioned before). Did you already have concerns before about whether 60 x 60 cm (24 x 24 inches) would work?
Although FERMACELL allows the installation of larger-format tiles or panels on their gypsum fiberboards above wooden beam ceilings, they require the tiles to be at least 15mm (0.6 inches) thick and have an edge length of up to 80cm (31.5 inches).
A critical factor that remains unaddressed is the unavoidable deflection of the substrate.
To reiterate: installing tiles up to 30cm x 30cm (12 inches x 12 inches) is uncritical, as any stresses caused by bending moments can be neutralized in the joints.
A critical factor that remains unaddressed is the unavoidable deflection of the substrate.
To reiterate: installing tiles up to 30cm x 30cm (12 inches x 12 inches) is uncritical, as any stresses caused by bending moments can be neutralized in the joints.
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