ᐅ Floor installer refuses to proceed due to residual moisture in the subfloor.
Created on: 29 Dec 2022 21:57
P
pim1985Hello everyone,
we have the following problem with our parquet installer (a small family business in NRW). He refuses to lay the parquet because the CM value from the last measurement is 0.44 percent. He expects a value of 0.3 percent. Our site manager (from the developer, by the way, we were very satisfied with the construction of the house, final inspection took place in mid-November) believes that a value of 0.5 percent is sufficient.
Here are further details regarding the situation:
- New build,
- Anhydrite screed
- Underfloor heating
- Functional heating started on 20.09.2022 / ended on 12.10.2022. The heating was done using an electric heating unit.
The underfloor heating has been running at full power for about 4 weeks.
Our neighbors (semi-detached house) installed vinyl flooring about 2 weeks ago and are already living there. The other neighbors in the detached houses (all three houses were built at the same time) also laid vinyl today and will move in soon. Our screed was installed first...
Apparently, the desired value will be reached next week in the upstairs area. The value on the ground floor, according to the parquet installer’s digital device, has remained unchanged...
We are quite desperate and don’t really know when we can move in.
What do you think about using a PU (polyurethane) moisture barrier/primer? It is supposed to reduce the residual moisture quickly. Would this be a sensible solution, or is there something else that could help?
we have the following problem with our parquet installer (a small family business in NRW). He refuses to lay the parquet because the CM value from the last measurement is 0.44 percent. He expects a value of 0.3 percent. Our site manager (from the developer, by the way, we were very satisfied with the construction of the house, final inspection took place in mid-November) believes that a value of 0.5 percent is sufficient.
Here are further details regarding the situation:
- New build,
- Anhydrite screed
- Underfloor heating
- Functional heating started on 20.09.2022 / ended on 12.10.2022. The heating was done using an electric heating unit.
The underfloor heating has been running at full power for about 4 weeks.
Our neighbors (semi-detached house) installed vinyl flooring about 2 weeks ago and are already living there. The other neighbors in the detached houses (all three houses were built at the same time) also laid vinyl today and will move in soon. Our screed was installed first...
Apparently, the desired value will be reached next week in the upstairs area. The value on the ground floor, according to the parquet installer’s digital device, has remained unchanged...
We are quite desperate and don’t really know when we can move in.
What do you think about using a PU (polyurethane) moisture barrier/primer? It is supposed to reduce the residual moisture quickly. Would this be a sensible solution, or is there something else that could help?
M
Myrna_Loy29 Dec 2022 23:21Are you having wood flooring installed or vinyl as well? With wood, the residual moisture content is more critical, especially if the substrate is also wood and not MDF or something similar. I’m not familiar with the exact values, but I’m sure there is a DIN standard or a recommendation from the chamber on this. If the specialist contractor handles it that way, I would rely on their assessment, because the construction manager can say a lot without being liable.
You probably have little choice but to satisfy the floor layer enough for them to agree to install the flooring. Not only if you have no alternative (another floor layer) should you take their concerns seriously. With anhydrite screed, the large amount of mixing water is a problem that must be resolved for glued parquet flooring applied directly on it. Surely, @KlaRa can provide more information on this.
A quick search also shows that the value of 0.3 CM-% is commonly cited as decisive. Remember: A tradesperson is liable even if you sign a waiver of liability!
Excerpt from the text below (source *bgbau*):
For calcium sulfate screeds, the moisture content must be ≤ 0.5 CM-% according to DIN 18560 (heated also ≤ 0.5 CM-%). However, for trades related to floor installation (laying floor coverings, parquet, and ceramic tiles), 0.3 CM-% is the relevant threshold.
*The limit values for calcium sulfate screeds were raised during the revision of DIN 18560-1, but flooring companies still often refer to the 0.3 CM-% limit.
What to do if the residual moisture is too high?
If the residual moisture of the screed is too high, the screed needs more time—possibly supported by measures such as air dryers—to reach suitable readiness for covering. Unfortunately, this usually does not fit into most construction schedules, especially since the drying process slows down over time.
Therefore, a common method is to use a reactive moisture barrier. This is a polymer layer applied to the surface of the screed that significantly reduces the water vapor diffusion rate. These systems typically form highly cross-linked, water-resistant, and saponification-stable polymers with a low water vapor diffusion rate, protecting both the adhesive and the floor covering from moisture. Epoxy resins are most often used for this. However, their application poses a risk of allergic skin reactions for individuals. Technically proven alternatives with considerably lower health risks are polyurethane products (isocyanates) as well as dispersions.
A quick search also shows that the value of 0.3 CM-% is commonly cited as decisive. Remember: A tradesperson is liable even if you sign a waiver of liability!
Excerpt from the text below (source *bgbau*):
For calcium sulfate screeds, the moisture content must be ≤ 0.5 CM-% according to DIN 18560 (heated also ≤ 0.5 CM-%). However, for trades related to floor installation (laying floor coverings, parquet, and ceramic tiles), 0.3 CM-% is the relevant threshold.
*The limit values for calcium sulfate screeds were raised during the revision of DIN 18560-1, but flooring companies still often refer to the 0.3 CM-% limit.
What to do if the residual moisture is too high?
If the residual moisture of the screed is too high, the screed needs more time—possibly supported by measures such as air dryers—to reach suitable readiness for covering. Unfortunately, this usually does not fit into most construction schedules, especially since the drying process slows down over time.
Therefore, a common method is to use a reactive moisture barrier. This is a polymer layer applied to the surface of the screed that significantly reduces the water vapor diffusion rate. These systems typically form highly cross-linked, water-resistant, and saponification-stable polymers with a low water vapor diffusion rate, protecting both the adhesive and the floor covering from moisture. Epoxy resins are most often used for this. However, their application poses a risk of allergic skin reactions for individuals. Technically proven alternatives with considerably lower health risks are polyurethane products (isocyanates) as well as dispersions.
schubert7930 Dec 2022 06:49The question is how the residual moisture is supposed to decrease now when it hasn't gone down in the last 2 months. Sanding?
schubert79 schrieb:
The question is just how the residual moisture is supposed to decrease now, if it hasn’t dropped in the last 2 months. Sanding? The floor was sanded about a week ago. Our site supervisor suggested this weeks ago, but the floor installer only carried it out a week ago. Are polyurethane products suitable for an anhydrite screed with underfloor heating?
Hello "pim1985".
In this case, the answer is not straightforward.
From a technical standpoint, the current state of the art is as "i_b_n_a_n" described it. According to the flooring professionals’ guidelines, this corresponds to a CM residual moisture value of 0.5 CM-% for underfloor heating and calcium sulfate screeds, as also listed in the current DIN 18365 standard.
However, this is contrasted by the opinion of parquet installers (as well as industry associations). At the moment, there are actually two opposing groups in a dispute, with "the power" seemingly shaped by industry lobbyists who participate in the DIN committees.
In fact, the 0.5 CM-% value has been the recognized state of the art without reported damage for years in Switzerland.
Back in Germany, the parquet installers’ "fear" of being held liable for moisture damage is, in my personal view, quite understandable.
Moreover, the sample extraction from the screed cross-section differs: flooring professionals typically take samples only from the upper third, while parquet installers prefer to take their samples across the entire cross-section when determining residual moisture content.
So, it is not easy to clearly answer your question purely based on technical regulations.
And DIN?
Well, the assumption is that a DIN standard accurately reflects the state of the art at the time it is published.
However, anyone professionally involved with building damage and standards knows this is often not the case.
Also, regarding the suggestion in one of the follow-up posts to apply a synthetic resin-based moisture barrier to your question, "pim1985", I can only strongly advise against this!
This solution, which may work in practice with cement screeds depending on the manufacturer—or may not—must absolutely not be used with calcium sulfate screeds! Trapped moisture, whether as excessive residual moisture or penetrating moisture, is "deadly" for moisture-sensitive calcium sulfate screeds. Excess moisture leads to decalcification. The result: the screed softens, at least at the interface of the barrier.
So what to do in the described situation?
On one hand, there is pressure from the client to move in; on the other, the parquet installer’s legitimate concern about potential damage. I would personally take three samples from the full screed cross-section at different locations, immediately seal them in double, resealable PE bags, and dry these as soon as possible using the gravimetric method at 45°C (113°F) until weight constancy is reached.
This method is admittedly uncommon in everyday trade practice, but it is used by floor technology experts when clear results are required.
Since both methods, gravimetric and CM, yield values of different dimensions (mass-% versus CM-%), but the difference in results is practically zero up to 0.5, a result below 0.5 CM-% can be accepted as ready for installation if the sample is taken from the entire cross-section. Because the gravimetric method in the drying oven tends to show slightly higher (and correct) values, a safety margin is ensured.
-------------------------------------------------------
I further suggest that you print out this article and give it to the site manager—whose view is quite correct—and to the parquet installer, who also has a reasonable but contrasting opinion.
Ultimately, it is not important who held which opinion when; what matters is that moisture-related floor damage does not occur later on!
-------------------------------
Good luck: KlaRa
In this case, the answer is not straightforward.
From a technical standpoint, the current state of the art is as "i_b_n_a_n" described it. According to the flooring professionals’ guidelines, this corresponds to a CM residual moisture value of 0.5 CM-% for underfloor heating and calcium sulfate screeds, as also listed in the current DIN 18365 standard.
However, this is contrasted by the opinion of parquet installers (as well as industry associations). At the moment, there are actually two opposing groups in a dispute, with "the power" seemingly shaped by industry lobbyists who participate in the DIN committees.
In fact, the 0.5 CM-% value has been the recognized state of the art without reported damage for years in Switzerland.
Back in Germany, the parquet installers’ "fear" of being held liable for moisture damage is, in my personal view, quite understandable.
Moreover, the sample extraction from the screed cross-section differs: flooring professionals typically take samples only from the upper third, while parquet installers prefer to take their samples across the entire cross-section when determining residual moisture content.
So, it is not easy to clearly answer your question purely based on technical regulations.
And DIN?
Well, the assumption is that a DIN standard accurately reflects the state of the art at the time it is published.
However, anyone professionally involved with building damage and standards knows this is often not the case.
Also, regarding the suggestion in one of the follow-up posts to apply a synthetic resin-based moisture barrier to your question, "pim1985", I can only strongly advise against this!
This solution, which may work in practice with cement screeds depending on the manufacturer—or may not—must absolutely not be used with calcium sulfate screeds! Trapped moisture, whether as excessive residual moisture or penetrating moisture, is "deadly" for moisture-sensitive calcium sulfate screeds. Excess moisture leads to decalcification. The result: the screed softens, at least at the interface of the barrier.
So what to do in the described situation?
On one hand, there is pressure from the client to move in; on the other, the parquet installer’s legitimate concern about potential damage. I would personally take three samples from the full screed cross-section at different locations, immediately seal them in double, resealable PE bags, and dry these as soon as possible using the gravimetric method at 45°C (113°F) until weight constancy is reached.
This method is admittedly uncommon in everyday trade practice, but it is used by floor technology experts when clear results are required.
Since both methods, gravimetric and CM, yield values of different dimensions (mass-% versus CM-%), but the difference in results is practically zero up to 0.5, a result below 0.5 CM-% can be accepted as ready for installation if the sample is taken from the entire cross-section. Because the gravimetric method in the drying oven tends to show slightly higher (and correct) values, a safety margin is ensured.
-------------------------------------------------------
I further suggest that you print out this article and give it to the site manager—whose view is quite correct—and to the parquet installer, who also has a reasonable but contrasting opinion.
Ultimately, it is not important who held which opinion when; what matters is that moisture-related floor damage does not occur later on!
-------------------------------
Good luck: KlaRa
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