Dear forum,
I hope this is the right section for my question. I bought a condominium and hired a plumber to install a 3cm (1¼ inch) deep, 90x90cm (35x35 inch) shower tray. I discussed this with him before the screed was laid. He planned to place a board to leave space in the screed so the tray could be recessed. Now it turns out this was forgotten. The tiler says it won’t work and that the tray will stick out by 1.5cm (⅝ inch).
My question: it would now be necessary to remove an area of 90x90cm (35x35 inch), minus the 30x30cm (12x12 inch) hole for the drain, at a depth of 2cm (¾ inch). Do I have a chance? Removing the material with a chisel probably won’t work, or can this be done with a milling machine?
Thanks in advance.
Good luck, Frank
I hope this is the right section for my question. I bought a condominium and hired a plumber to install a 3cm (1¼ inch) deep, 90x90cm (35x35 inch) shower tray. I discussed this with him before the screed was laid. He planned to place a board to leave space in the screed so the tray could be recessed. Now it turns out this was forgotten. The tiler says it won’t work and that the tray will stick out by 1.5cm (⅝ inch).
My question: it would now be necessary to remove an area of 90x90cm (35x35 inch), minus the 30x30cm (12x12 inch) hole for the drain, at a depth of 2cm (¾ inch). Do I have a chance? Removing the material with a chisel probably won’t work, or can this be done with a milling machine?
Thanks in advance.
Good luck, Frank
Hello Frank,
We have already met in one of the other forums here.
The bathtub must be supported by the floor slab/concrete ceiling to carry the load!
Trying to level the screed, which rests on insulation layers, by grinding or milling it down is pointless!
Reducing its thickness also decreases the screed’s load-bearing capacity.
So, what should be done?
The solution is simple:
First, you need to determine the area where the screed must be cut out later.
That part has to be removed to the necessary extent. This is not problematic, especially since at least one side is adjacent to a wall!
At the time of execution (only use a cutting technique with a good dust extraction system!!!), you will instruct the plumbing contractor who installed the underfloor heating to turn off the heating and depressurize the system.
They must also bring materials to reconnect any heating elements that might be severed during the screed removal.
The screed area is cut out, the damaged heating elements are reconnected, water is refilled into the heating system, and then everything can continue as usual!
Floating screeds in residential construction are designed for a vertical uniform load of about 150kg/m² (31 pounds per square foot). The edge areas are subject to higher stress than the central parts.
A filled bathtub with a person quickly exceeds 150kg/m² (31 pounds per square foot).
The screed can (and realistically will) break under this load if the bathtub is placed directly on the “floating screed.”
This damage scenario is real—I can confirm this from my own professional experience.
---------------------------
Best regards, KlaRa
We have already met in one of the other forums here.
The bathtub must be supported by the floor slab/concrete ceiling to carry the load!
Trying to level the screed, which rests on insulation layers, by grinding or milling it down is pointless!
Reducing its thickness also decreases the screed’s load-bearing capacity.
So, what should be done?
The solution is simple:
First, you need to determine the area where the screed must be cut out later.
That part has to be removed to the necessary extent. This is not problematic, especially since at least one side is adjacent to a wall!
At the time of execution (only use a cutting technique with a good dust extraction system!!!), you will instruct the plumbing contractor who installed the underfloor heating to turn off the heating and depressurize the system.
They must also bring materials to reconnect any heating elements that might be severed during the screed removal.
The screed area is cut out, the damaged heating elements are reconnected, water is refilled into the heating system, and then everything can continue as usual!
Floating screeds in residential construction are designed for a vertical uniform load of about 150kg/m² (31 pounds per square foot). The edge areas are subject to higher stress than the central parts.
A filled bathtub with a person quickly exceeds 150kg/m² (31 pounds per square foot).
The screed can (and realistically will) break under this load if the bathtub is placed directly on the “floating screed.”
This damage scenario is real—I can confirm this from my own professional experience.
---------------------------
Best regards, KlaRa
@KlaRa,
no, this is not a bathtub but a shower tray. The plumber just forgot to install the adapter board before the screed was poured, so the tray sits 1.5 cm (0.6 inches) too high; otherwise it would have been 1.5 cm (0.6 inches) lower. The heating pipe is about 4–5 cm (1.6–2.0 inches) lower. That means if the board had been installed, the stability would also be ensured, but I need to discuss this with the plumber. I don’t want to risk the warranty right now; I just wanted to know if it’s possible to remove material afterwards.
Good luck, Frank
no, this is not a bathtub but a shower tray. The plumber just forgot to install the adapter board before the screed was poured, so the tray sits 1.5 cm (0.6 inches) too high; otherwise it would have been 1.5 cm (0.6 inches) lower. The heating pipe is about 4–5 cm (1.6–2.0 inches) lower. That means if the board had been installed, the stability would also be ensured, but I need to discuss this with the plumber. I don’t want to risk the warranty right now; I just wanted to know if it’s possible to remove material afterwards.
Good luck, Frank
Hello Frank,
I simply misunderstood the term "duschwanne" (shower tray).
However, even with a shower pan, the installation area should be recessed in the screed.
One of the fundamental questions is:
“What was specified at the time regarding the screed work?”
Was the lowering (which is actually not permitted according to screed standards 13813 and 18353) requested?
If YES, then recessing would be a typical correction, free of charge for the client. There would certainly be no need for legal disputes!
But in any case: the (technical) problem is well solvable!
If it is a factory-made, i.e., prefabricated shower tray, the connection of the waterproofing (to the surface waterproofing of the screed) is most likely already provided and therefore unproblematic. If it is not planned, there are also solutions here! You just need to know what you are doing from a construction perspective.
However, the shower tray should rest on the concrete slab or floor slab because a screed of reduced thickness on an insulation layer would not safely bear these loads, even if they are only about 1 kN (225 pounds-force), without future risk! This is because the shower tray is placed on the screed edge, where the internal stresses caused by point loads and bending moments are quite significant.
Shower trays are supplied with height-adjustable supports, so this can also be technically solved well.
It would be different with a shower pan constructed by hand using, for example, mortar-sloped plates.
Although that is also possible, several important points must be considered to avoid complaints later on.
---------------------
Best regards and good luck, KlaRa
I simply misunderstood the term "duschwanne" (shower tray).
However, even with a shower pan, the installation area should be recessed in the screed.
One of the fundamental questions is:
“What was specified at the time regarding the screed work?”
Was the lowering (which is actually not permitted according to screed standards 13813 and 18353) requested?
If YES, then recessing would be a typical correction, free of charge for the client. There would certainly be no need for legal disputes!
But in any case: the (technical) problem is well solvable!
If it is a factory-made, i.e., prefabricated shower tray, the connection of the waterproofing (to the surface waterproofing of the screed) is most likely already provided and therefore unproblematic. If it is not planned, there are also solutions here! You just need to know what you are doing from a construction perspective.
However, the shower tray should rest on the concrete slab or floor slab because a screed of reduced thickness on an insulation layer would not safely bear these loads, even if they are only about 1 kN (225 pounds-force), without future risk! This is because the shower tray is placed on the screed edge, where the internal stresses caused by point loads and bending moments are quite significant.
Shower trays are supplied with height-adjustable supports, so this can also be technically solved well.
It would be different with a shower pan constructed by hand using, for example, mortar-sloped plates.
Although that is also possible, several important points must be considered to avoid complaints later on.
---------------------
Best regards and good luck, KlaRa
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