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.
What type of screed is this? What you should avoid is causing drafts on the screed. If you fully open the windows twice daily, you create about one hour of draft inside the house every day. I tried ventilating with windows tilted open.
I am not an expert and cannot say if something is wrong with your screed. However, in our case, the windows were still damp at the bottom edge in the morning even after 4 to 5 weeks. At the beginning, we also ventilated too little for a long time.
Before grinding the screed based on assumptions, there is the option to break open the screed at one spot to inspect the lower layer. This must be done where the "pinöppel" is embedded in the screed.
I am not an expert and cannot say if something is wrong with your screed. However, in our case, the windows were still damp at the bottom edge in the morning even after 4 to 5 weeks. At the beginning, we also ventilated too little for a long time.
Before grinding the screed based on assumptions, there is the option to break open the screed at one spot to inspect the lower layer. This must be done where the "pinöppel" is embedded in the screed.
@Stefan2.84:
Please do not take away the only (official) method the following floor installer has to perform a CM residual moisture measurement!! Leave everything as it is, without opening the screed construction. Moisture cannot be seen, only measured.
For this reason, it is unclear why – without any necessity and especially without any realistic chance of obtaining useful results – the only properly designated measuring point in the room should be opened.
Regarding moisture in the room:
Nowhere is it stated that condensation must occur on windows during the installation of screed. So why assume a special situation, which can actually occur in new buildings may, as a prerequisite?
About sanding:
It is indeed true that calcium sulfate flowing screeds are sanded in order to open the surface by releasing the pores, allowing water transport from the screed structure to the room air.
But!
This requires the necessity to perform such a measure. Such necessity arises only and exclusively after several weeks of ventilation when a residual moisture measurement (!) confirms that the screed still has too high residual moisture.
From what I read in your post, none of that has happened so far; everything is based on assumptions and misinformation, thus on “fearmongering.”
It’s best to leave the matter to the professionals.
The floor installer will carry out a CM test at the designated measuring point, record everything in their report, and provide it to you (as the client).
Only then can it be decided whether any additional measures are needed before installing the floor covering.
If you open the screed structure at the measuring point just out of curiosity, the floor installer will no longer be able to perform a measurement, will express concerns, and will present you with the decision on how to proceed. You will then assume the responsibility and risk, even as a layperson.
Because the measuring point where they can safely open the heated screed (which is likely the case here, given that measuring sites are marked) will no longer be available.
So (deliberately put somewhat informally):
Hands off the screed and wait for the expert (in this case: the floor installer) to come!
Wishing you continued success:
KlaRa
Please do not take away the only (official) method the following floor installer has to perform a CM residual moisture measurement!! Leave everything as it is, without opening the screed construction. Moisture cannot be seen, only measured.
For this reason, it is unclear why – without any necessity and especially without any realistic chance of obtaining useful results – the only properly designated measuring point in the room should be opened.
Regarding moisture in the room:
Nowhere is it stated that condensation must occur on windows during the installation of screed. So why assume a special situation, which can actually occur in new buildings may, as a prerequisite?
About sanding:
It is indeed true that calcium sulfate flowing screeds are sanded in order to open the surface by releasing the pores, allowing water transport from the screed structure to the room air.
But!
This requires the necessity to perform such a measure. Such necessity arises only and exclusively after several weeks of ventilation when a residual moisture measurement (!) confirms that the screed still has too high residual moisture.
From what I read in your post, none of that has happened so far; everything is based on assumptions and misinformation, thus on “fearmongering.”
It’s best to leave the matter to the professionals.
The floor installer will carry out a CM test at the designated measuring point, record everything in their report, and provide it to you (as the client).
Only then can it be decided whether any additional measures are needed before installing the floor covering.
If you open the screed structure at the measuring point just out of curiosity, the floor installer will no longer be able to perform a measurement, will express concerns, and will present you with the decision on how to proceed. You will then assume the responsibility and risk, even as a layperson.
Because the measuring point where they can safely open the heated screed (which is likely the case here, given that measuring sites are marked) will no longer be available.
So (deliberately put somewhat informally):
Hands off the screed and wait for the expert (in this case: the floor installer) to come!
Wishing you continued success:
KlaRa
S
Stefan2.8425 Jun 2020 10:15Hello KlaRa,
thank you for your detailed explanation.
As with many things, there are always around 100 different opinions. For me, as a layperson, this naturally creates a lot of uncertainty. At a neighbor’s house, the calcium sulfate screed was tested after 7 weeks and was still too moist. The person conducting the measurement believed that sanding should have been done immediately after one week. The same was said by the tile installer, who, by the way, will also be installing my tiles. I then called the screed specialist. Dorte explained that the sanding is only a cleaning grind and has nothing to do with drying. This sanding should also be carried out by the following trade. So that means I will wait a few more weeks, then have it measured, and if it is still too moist, I will sand and wait a few more weeks again? Most people then ask themselves why not sand right away. It can really drive you crazy.
thank you for your detailed explanation.
As with many things, there are always around 100 different opinions. For me, as a layperson, this naturally creates a lot of uncertainty. At a neighbor’s house, the calcium sulfate screed was tested after 7 weeks and was still too moist. The person conducting the measurement believed that sanding should have been done immediately after one week. The same was said by the tile installer, who, by the way, will also be installing my tiles. I then called the screed specialist. Dorte explained that the sanding is only a cleaning grind and has nothing to do with drying. This sanding should also be carried out by the following trade. So that means I will wait a few more weeks, then have it measured, and if it is still too moist, I will sand and wait a few more weeks again? Most people then ask themselves why not sand right away. It can really drive you crazy.
Hello Stefan,
What you pointed out is (almost) entirely correct.
Ideally, the surface should be ground after one week to allow the screed to dry faster afterward. However, technically speaking, grinding is a service whose necessity can only be determined after confirming insufficient drying. And after one week, no screed (except those made with rapid cement or screed additives) can be dry.
The mandatory cleaning grind performed by the floor installer should not be confused with the initial grinding to improve drying!
Unfortunately, as the client, you need to invest time and be prepared to adapt to the circumstances!
The problem of calcium sulfate flowing screeds not drying properly is well known to me from my own experience. For example, a heated screed still showed significantly high moisture values even after six continuous weeks of heating and ventilation. This is due to the pore size and the associated moisture transport mechanism.
This makes the entire situation more complex than you might expect.
In such cases, it is the responsibility of my professional group to assess whether this constitutes a “defect” (a legal term), which can also be important in legal proceedings.
My recommendation to you:
Nothing has happened so far. There is no indication yet that the screed is unusually moist. As the saying goes, don’t make a mountain out of a molehill and wait to see what the floor installer will tell you about his results regarding the CM (calcium carbide) measurement.
Best regards, KlaRa
What you pointed out is (almost) entirely correct.
Ideally, the surface should be ground after one week to allow the screed to dry faster afterward. However, technically speaking, grinding is a service whose necessity can only be determined after confirming insufficient drying. And after one week, no screed (except those made with rapid cement or screed additives) can be dry.
The mandatory cleaning grind performed by the floor installer should not be confused with the initial grinding to improve drying!
Unfortunately, as the client, you need to invest time and be prepared to adapt to the circumstances!
The problem of calcium sulfate flowing screeds not drying properly is well known to me from my own experience. For example, a heated screed still showed significantly high moisture values even after six continuous weeks of heating and ventilation. This is due to the pore size and the associated moisture transport mechanism.
This makes the entire situation more complex than you might expect.
In such cases, it is the responsibility of my professional group to assess whether this constitutes a “defect” (a legal term), which can also be important in legal proceedings.
My recommendation to you:
Nothing has happened so far. There is no indication yet that the screed is unusually moist. As the saying goes, don’t make a mountain out of a molehill and wait to see what the floor installer will tell you about his results regarding the CM (calcium carbide) measurement.
Best regards, KlaRa
Stefan2.84 schrieb:
I have not noticed any moisture development anywhere yet (on windows or on the concrete ceiling)? Really nothing. Have you set up a hygrometer?
Apart from that, condensation requires high humidity and a temperature difference.
Here, it has been at least 15°C (59°F) at night for weeks, and usually 25 to now 35°C (77 to 95°F) during the day.
S
Stefan2.8425 Jun 2020 12:52I just wanted to check if there’s anything I can optimize here. So far, nothing significant has happened that requires much thought. Starting next week, the heating system will be running. I’ll set up a hygrometer to monitor the humidity. Of course, I don’t want to waste time if the screed isn’t dry yet. That’s why I’m asking about sanding.
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