ᐅ Cement screed without chemical additives does not properly dry.
Created on: 25 Nov 2025 13:00
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BrnZck91Hello everyone!
On September 3rd, we had 65mm (2.6 inches) of cement screed installed (without chemical additives).
The heating protocol was followed, and we ventilated the house three times daily for 10-20 minutes each time. Several calcium carbide (CM) measurements have already been taken, and even after following the heating schedule, we consistently maintained heating up to 30°C (86°F).
During this time, plasterers and painters were also present. However, that was almost three weeks ago now.
Tomorrow the screed will have been laid for 12 weeks, and the last CM measurement taken last Monday still showed 2.6%.
On the recommendation of the screed company, we have since increased the heating to 45-50°C (113-122°F) up to today and also set up a construction dryer and a smaller room dehumidifier. Someone from the screed company visited today and couldn’t explain the situation. Inside the house, there is no noticeable moisture. It does not smell damp. There is no condensation on the windows, and the humidity levels on three hygrometers placed throughout the house range between 35-44%.
Still, the electronic moisture meter shows values between 1.7 and 2.2, and when the meter is placed in the hole left by earlier CM measurements, it even rises up to 2.7. I am at a loss.
The screed installer contacted another floor installer who recommended lowering the heating to 25°C (77°F), so that the air temperature stabilizes around 20°C (68°F). The reasoning was that the devices do not work correctly at higher temperatures (currently the air temperature is over 35°C (95°F)). The electronic moisture meter even showed 3.0% on the concrete stairs, which seems unlikely. But the CM measurements were done by the tiler and flooring installer, often together using two different devices alternately.
We only have one more measuring point left, and the furniture is arriving on December 9th.
The flooring installer also suggested applying an epoxy resin coating to prevent moisture from rising. To allow space for any ascending moisture, he plans to leave out the baseboards for now. This is not possible in the bathrooms, of course, since there will be tiles on the floor and walls.
I really hope someone here can help. I am getting desperate.
On September 3rd, we had 65mm (2.6 inches) of cement screed installed (without chemical additives).
The heating protocol was followed, and we ventilated the house three times daily for 10-20 minutes each time. Several calcium carbide (CM) measurements have already been taken, and even after following the heating schedule, we consistently maintained heating up to 30°C (86°F).
During this time, plasterers and painters were also present. However, that was almost three weeks ago now.
Tomorrow the screed will have been laid for 12 weeks, and the last CM measurement taken last Monday still showed 2.6%.
On the recommendation of the screed company, we have since increased the heating to 45-50°C (113-122°F) up to today and also set up a construction dryer and a smaller room dehumidifier. Someone from the screed company visited today and couldn’t explain the situation. Inside the house, there is no noticeable moisture. It does not smell damp. There is no condensation on the windows, and the humidity levels on three hygrometers placed throughout the house range between 35-44%.
Still, the electronic moisture meter shows values between 1.7 and 2.2, and when the meter is placed in the hole left by earlier CM measurements, it even rises up to 2.7. I am at a loss.
The screed installer contacted another floor installer who recommended lowering the heating to 25°C (77°F), so that the air temperature stabilizes around 20°C (68°F). The reasoning was that the devices do not work correctly at higher temperatures (currently the air temperature is over 35°C (95°F)). The electronic moisture meter even showed 3.0% on the concrete stairs, which seems unlikely. But the CM measurements were done by the tiler and flooring installer, often together using two different devices alternately.
We only have one more measuring point left, and the furniture is arriving on December 9th.
The flooring installer also suggested applying an epoxy resin coating to prevent moisture from rising. To allow space for any ascending moisture, he plans to leave out the baseboards for now. This is not possible in the bathrooms, of course, since there will be tiles on the floor and walls.
I really hope someone here can help. I am getting desperate.
schubert7925 Nov 2025 17:36We had to sand the screed completely once. A layer had formed on it. I don’t remember the exact term. After a very short time, the problem was resolved.
schubert79 schrieb:
We had to grind the screed completely once. A layer had formed on top. I don't remember the exact term. The problem was resolved after a very short time. Do you remember how much you ground off? Our flooring installer did the same last week.We faced a similar issue. In our case, the flooring installer initially used an electronic measuring device. Even after 8 weeks in the summer, the device supposedly still showed a residual moisture content of 3.5%. After doing a lot of research, I learned that these devices are not very reliable for measuring moisture in floors. 1. They are designed to measure about 6cm (2.4 inches) deep. 2. We have underfloor heating. 3. The device apparently needs to be recalibrated in each room and the sensor ball shouldn’t be touched beforehand.
After we insisted, the installer performed a proper CM measurement using a manometer and pressure testing, and fortunately, the value was only 0.7%.
After we insisted, the installer performed a proper CM measurement using a manometer and pressure testing, and fortunately, the value was only 0.7%.
Summer27 schrieb:
We faced a similar issue. However, in our case, the flooring installer initially always used one of those electronic measuring devices. Even after 8 weeks in the summer, they claimed the residual moisture was still at 3.5%. After a lot of research, I learned that these devices are not very reliable for floor measurements. 1. They are supposed to measure 6cm (2.4 inches) deep. 2. We have underfloor heating. 3. You apparently need to recalibrate the device in each room and definitely must not touch the sensor ball beforehand.
When, at our insistence, he finally performed a proper CM measurement using a manometer and pressure test, the value was fortunately only 0.7%. However, our last CM measurement 8 days ago was unfortunately still 2.6%.
What is the ideal room temperature for such a measurement? What factors could potentially affect the result?
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