We realized after 12 days that our installer had set the wrong drying program. It has been running constantly at 30 degrees Celsius (86°F) for 12 days. This is an electrically powered external device, not the heat pump.
The installer is coming tomorrow. What do you recommend? I will have the screed moisture measured today. However, my main concern is the expansion. If I increase the temperature from 30 to 40 degrees Celsius (86 to 104°F) tomorrow, then from Friday to Saturday to 50 degrees Celsius (122°F), and keep it there for two days until Monday, will that be sufficient?
We have already scheduled all subsequent work steps with all contractors after the drying program. It would be a disaster if we had to extend the program.
The installer is coming tomorrow. What do you recommend? I will have the screed moisture measured today. However, my main concern is the expansion. If I increase the temperature from 30 to 40 degrees Celsius (86 to 104°F) tomorrow, then from Friday to Saturday to 50 degrees Celsius (122°F), and keep it there for two days until Monday, will that be sufficient?
We have already scheduled all subsequent work steps with all contractors after the drying program. It would be a disaster if we had to extend the program.
30 degrees Celsius (86°F) is still too low for functional heating. The maximum design temperature should be reached, usually 35 degrees Celsius (95°F).
50 degrees Celsius (122°F) is outdated.
During the subsequent drying heating phase (surface readiness heating), the goal is to remove residual moisture; otherwise, tiling and parquet flooring won’t work (measured in cm). This is always uncertain. Sometimes an additional 1-2 weeks of heating is needed, which should be planned as a buffer.
Self-made stress. There is no guarantee of surface readiness after a set number of days.
50 degrees Celsius (122°F) is outdated.
During the subsequent drying heating phase (surface readiness heating), the goal is to remove residual moisture; otherwise, tiling and parquet flooring won’t work (measured in cm). This is always uncertain. Sometimes an additional 1-2 weeks of heating is needed, which should be planned as a buffer.
Tx-25 schrieb:
It would therefore be a disaster if we have to extend the program.
Self-made stress. There is no guarantee of surface readiness after a set number of days.
Hello questioner.
This is confusion multiplied by ten.
You mention a "drying program" and refer to an electric (external) heating device.
What is that supposed to achieve? It can (and will) support the drying out of the screed, but as others have already pointed out, the first step here should be the "functional heating."
This serves, on the one hand, to check whether all parts of the underfloor heating system are working properly and leak-free, and on the other hand, the slow heating removes the stresses in the screed that occur due to drying.
----------------
Confusion 2:
"But I am concerned about the expansion."
What does that mean? What do you fear will expand, when, and under what circumstances?
-----------------
Confusion 3:
"The installer is coming tomorrow. (...) If I raise the temperature from 30 to 40 tomorrow, then from Friday to Saturday to 50, and leave it like that for two days until Monday, will that be enough?"
So the underfloor heating is working again?
"It would therefore be a disaster if we have to extend the program."
I would be happy to take you with me on my expert inspections so you can see in practice what is actually understood by a "disaster."
Currently, I am at a very high-quality residential building where all the porcelain tiles in all rooms have cracked due to improper or not performed drying measures of the heated screed, exactly what you are facing now.
The owner lives in the property with their family; all installations—as well as the floor tiles—have to be removed, the furniture temporarily stored, the owners relocated to a hotel, and the resulting construction debris lifted over the house by a crane and placed into the debris container.
Those are costs that—in a situation like yours—would have to be paid out of your own pocket.
No, a time delay to prevent such damage should not be called a "disaster."
Ignorance and/or negligence (which I do not wish to assume here) certainly are!
----------------
Also, what does "2% was reached" mean? Was that mass percent, calcium carbide moisture (CM) percent, or a value from a device scaled 0–100?
How and over what cross-section of the screed was the measurement taken, and by whom?
Is there a written report including the batch weight, pressure build-up in the pressure bottle, and the residual moisture result?
As you can see, construction practice is, unfortunately, not as simple as it might seem.
Best regards: KlaRa
This is confusion multiplied by ten.
You mention a "drying program" and refer to an electric (external) heating device.
What is that supposed to achieve? It can (and will) support the drying out of the screed, but as others have already pointed out, the first step here should be the "functional heating."
This serves, on the one hand, to check whether all parts of the underfloor heating system are working properly and leak-free, and on the other hand, the slow heating removes the stresses in the screed that occur due to drying.
----------------
Confusion 2:
"But I am concerned about the expansion."
What does that mean? What do you fear will expand, when, and under what circumstances?
-----------------
Confusion 3:
"The installer is coming tomorrow. (...) If I raise the temperature from 30 to 40 tomorrow, then from Friday to Saturday to 50, and leave it like that for two days until Monday, will that be enough?"
So the underfloor heating is working again?
"It would therefore be a disaster if we have to extend the program."
I would be happy to take you with me on my expert inspections so you can see in practice what is actually understood by a "disaster."
Currently, I am at a very high-quality residential building where all the porcelain tiles in all rooms have cracked due to improper or not performed drying measures of the heated screed, exactly what you are facing now.
The owner lives in the property with their family; all installations—as well as the floor tiles—have to be removed, the furniture temporarily stored, the owners relocated to a hotel, and the resulting construction debris lifted over the house by a crane and placed into the debris container.
Those are costs that—in a situation like yours—would have to be paid out of your own pocket.
No, a time delay to prevent such damage should not be called a "disaster."
Ignorance and/or negligence (which I do not wish to assume here) certainly are!
----------------
Also, what does "2% was reached" mean? Was that mass percent, calcium carbide moisture (CM) percent, or a value from a device scaled 0–100?
How and over what cross-section of the screed was the measurement taken, and by whom?
Is there a written report including the batch weight, pressure build-up in the pressure bottle, and the residual moisture result?
As you can see, construction practice is, unfortunately, not as simple as it might seem.
Best regards: KlaRa
Hello @KlaRa.
Confusion 1: The screed is dried below the underfloor heating. However, not with our heat pump but with a different device connected to the circuit. So it is not a construction dryer.
Confusion 2: By expansion, I mean the movement/stress build-up and release in the screed. Can this be achieved without 50 degrees? The heat pump will only run at 35 degrees anyway. So is heating up to 50 degrees necessary?
Confusion 3: Explained in point 1. I agree it’s not a real disaster. But it does throw everything off for us.
The screed was broken open. Measurements were taken as you described, with calibration weight and pressure buildup in the pressure bottle. The result is not documented in writing. Measurements were done by a professional woman from the family.
Our current plan is to heat to 45 degrees tomorrow, then 50 degrees on Saturday. Hold for 2 days, then reduce in 10-degree steps. The screed is already dry. The function of the pipes is tested then, right?
Confusion 1: The screed is dried below the underfloor heating. However, not with our heat pump but with a different device connected to the circuit. So it is not a construction dryer.
Confusion 2: By expansion, I mean the movement/stress build-up and release in the screed. Can this be achieved without 50 degrees? The heat pump will only run at 35 degrees anyway. So is heating up to 50 degrees necessary?
Confusion 3: Explained in point 1. I agree it’s not a real disaster. But it does throw everything off for us.
The screed was broken open. Measurements were taken as you described, with calibration weight and pressure buildup in the pressure bottle. The result is not documented in writing. Measurements were done by a professional woman from the family.
Our current plan is to heat to 45 degrees tomorrow, then 50 degrees on Saturday. Hold for 2 days, then reduce in 10-degree steps. The screed is already dry. The function of the pipes is tested then, right?
Hello questioner.
Perhaps I often assume too much technical knowledge from those asking questions, so I would like to apologize if my somewhat “direct” manner came across as harsh to you.
The stress buildup mentioned under point 2 is caused by drying. This does not require any additional heat input, for example from underfloor heating. Every screed dries out even without heating (otherwise all other unheated screeds would never be ready for covering).
Another point to clarify some common misunderstandings:
Functional heating is very often mistakenly understood by architects and site managers themselves as "ready-for-cover heating."
This technical misconception will cost a poor parquet installer approximately €750,000 in a recently inspected, very prestigious villa in Munich due to moisture damage and the complete replacement of the "Versailles pattern parquet."
The CM (calcium chloride) residual moisture measurements were indeed carried out professionally but were done far too early and, due to the size of the building, at too few locations.
No criticism of the specialist who conducted the measurements at your property!
However, based on my many years of experience, I distrust any CM measurement that I have not performed and analyzed myself.
Still, best of luck with all your further construction progress: KlaRa
Perhaps I often assume too much technical knowledge from those asking questions, so I would like to apologize if my somewhat “direct” manner came across as harsh to you.
The stress buildup mentioned under point 2 is caused by drying. This does not require any additional heat input, for example from underfloor heating. Every screed dries out even without heating (otherwise all other unheated screeds would never be ready for covering).
Another point to clarify some common misunderstandings:
Functional heating is very often mistakenly understood by architects and site managers themselves as "ready-for-cover heating."
This technical misconception will cost a poor parquet installer approximately €750,000 in a recently inspected, very prestigious villa in Munich due to moisture damage and the complete replacement of the "Versailles pattern parquet."
The CM (calcium chloride) residual moisture measurements were indeed carried out professionally but were done far too early and, due to the size of the building, at too few locations.
No criticism of the specialist who conducted the measurements at your property!
However, based on my many years of experience, I distrust any CM measurement that I have not performed and analyzed myself.
Still, best of luck with all your further construction progress: KlaRa
W
Wintersonne2 May 2020 20:05Dear KlaRa,
I am also interested in this now. After how many weeks (including heating the underfloor heating) can one be certain (if you don’t fully trust the calcium meter moisture measurement or the person conducting it) that the screed is ready for covering? (in the case of a calcium sulfate liquid screed).
How many weeks does it usually take without heating on average?
Are there any guidelines for this?
I am also interested in this now. After how many weeks (including heating the underfloor heating) can one be certain (if you don’t fully trust the calcium meter moisture measurement or the person conducting it) that the screed is ready for covering? (in the case of a calcium sulfate liquid screed).
How many weeks does it usually take without heating on average?
Are there any guidelines for this?
Hello "Wintersonne".
At first glance, your question seems straightforward, but there are many aspects to consider behind it. I will start by answering your question from a simplified perspective.
There are conventionally installed screeds, so-called wet screeds, made on both cement and calcium sulfate bases. The latter were formerly called "anhydrite screeds." Such screeds are installed in residential construction with nominal thicknesses of 45mm (1.8 inches) and, under favorable drying conditions on site, dry to readiness for covering in about 6 weeks. This rule applied to screed thicknesses up to 60mm (2.4 inches). For each additional centimeter, the drying time must be squared, so, for example, with a thickness of 80mm (3.1 inches) – meaning 2 cm (0.8 inches) extra thickness – you would calculate 6 weeks plus (2 cm squared = 4 weeks).
Flowing calcium sulfate screeds (abbreviated CAF) dry faster due to a different curing mechanism than cement screeds, so readiness for covering can be expected sooner. However, this does not mean the screed is actually ready. This must be confirmed by residual moisture measurement (the industry-standard method is the CM method).
------------------
That was the simplified explanation.
Due to demands from clients and planners for the shortest possible drying phase of screeds, the industry responded by offering so-called "screed additives," which are intended, among other things, to shorten the waiting time until readiness for covering. Some of these products work, others do not.
The major issue, however, is that all screeds with additives deviate from the DIN standard and are therefore classified as special screeds (which carries legal implications in some cases). In addition, the properties of the screed mortar have changed. For example, such screeds can no longer always be reliably measured with the CM method to check readiness for covering.
For the calcium sulfate flowing screeds you mentioned, matters have become even more complicated. There is no information in the literature, but we experts in the field notice that, due to manufacturers’ recipe changes, the pore sizes in the hardened flowing screed have become smaller. This has a significant (negative) impact on drying.
To summarize: Even in heated screeds, where thermal pressure would logically suggest a shorter release time for mixing water, the opposite has occurred—drying times have actually been extended.
----------------------------------
This means: readiness for covering can only be determined by CM measurements or by a DARR test (the latter is performed only by experts, not by a tradesperson).
According to current standards, for cement screeds up to 55mm (2.2 inches) thick, a drying time of 5-6 weeks can be expected; for CAF screeds (not heated screeds), about 7 days, assuming appropriate room climate (such as shock ventilation and external heating in winter).
I hope this (somewhat detailed) information has helped clarify things!
Best regards,
KlaRa
At first glance, your question seems straightforward, but there are many aspects to consider behind it. I will start by answering your question from a simplified perspective.
There are conventionally installed screeds, so-called wet screeds, made on both cement and calcium sulfate bases. The latter were formerly called "anhydrite screeds." Such screeds are installed in residential construction with nominal thicknesses of 45mm (1.8 inches) and, under favorable drying conditions on site, dry to readiness for covering in about 6 weeks. This rule applied to screed thicknesses up to 60mm (2.4 inches). For each additional centimeter, the drying time must be squared, so, for example, with a thickness of 80mm (3.1 inches) – meaning 2 cm (0.8 inches) extra thickness – you would calculate 6 weeks plus (2 cm squared = 4 weeks).
Flowing calcium sulfate screeds (abbreviated CAF) dry faster due to a different curing mechanism than cement screeds, so readiness for covering can be expected sooner. However, this does not mean the screed is actually ready. This must be confirmed by residual moisture measurement (the industry-standard method is the CM method).
------------------
That was the simplified explanation.
Due to demands from clients and planners for the shortest possible drying phase of screeds, the industry responded by offering so-called "screed additives," which are intended, among other things, to shorten the waiting time until readiness for covering. Some of these products work, others do not.
The major issue, however, is that all screeds with additives deviate from the DIN standard and are therefore classified as special screeds (which carries legal implications in some cases). In addition, the properties of the screed mortar have changed. For example, such screeds can no longer always be reliably measured with the CM method to check readiness for covering.
For the calcium sulfate flowing screeds you mentioned, matters have become even more complicated. There is no information in the literature, but we experts in the field notice that, due to manufacturers’ recipe changes, the pore sizes in the hardened flowing screed have become smaller. This has a significant (negative) impact on drying.
To summarize: Even in heated screeds, where thermal pressure would logically suggest a shorter release time for mixing water, the opposite has occurred—drying times have actually been extended.
----------------------------------
This means: readiness for covering can only be determined by CM measurements or by a DARR test (the latter is performed only by experts, not by a tradesperson).
According to current standards, for cement screeds up to 55mm (2.2 inches) thick, a drying time of 5-6 weeks can be expected; for CAF screeds (not heated screeds), about 7 days, assuming appropriate room climate (such as shock ventilation and external heating in winter).
I hope this (somewhat detailed) information has helped clarify things!
Best regards,
KlaRa
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