ᐅ The screed will not be fully dry after 10 weeks, even with a heating schedule.
Created on: 14 Oct 2022 17:17
J
joschua_85
Hello,
On July 12th, we had 7 cm (3 inches) of cement screed installed throughout the entire house.
Since there was no rush, we only started the heating program on September 24th. So the screed had actually been drying for about 11 weeks.
The majority of the water should be out by now; the floor coverings are next, which is why the hot air blower was turned on.
We heated according to the "program" provided by my heating technician, in coordination with the screed installer, until October 11th. I understand this is not the usual "standard program," which I personally think is preferable, since no new build needs a 55-degree Celsius (131°F) supply temperature nowadays. The screed will never see that with our heat pump. The maximum supply temperature according to calculations is 35 degrees Celsius (95°F).
Our heating schedule was as follows:
1: 30°C (86°F)
2: 35°C (95°F)
3-5: 45°C (113°F) (so the screed experienced a higher temperature)
6-12: 35°C (95°F)
13-17: 40°C (104°F) (after the first quick test, it was still too damp, so the supply temperature was raised again)
18: 35°C (95°F)
19: 30°C (86°F)
But hopefully, that’s not the main issue. I am still puzzled that after such a long time, my tiler still finds a CM (calcium carbide) moisture test unnecessary because his moisture meter (from GANN) still shows 65 digits. I understand the intention behind preliminary testing, but I don’t understand why everything still seems so damp?
Yes, I ventilate 3-4 times daily with cross-ventilation. I have two hygrometers in the house, and I ventilate as long as the humidity inside decreases, which is usually around 10 minutes. I do not want to connect multiple industrial dehumidifiers to the hot air blower because that would drive the cost through the roof.
My questions:
Should I keep the windows tilted open in principle? Even at night? Or keep them tilted open plus ventilate quickly during the day and close them at night? Or only ventilate quickly?
Should I avoid ventilation altogether in rainy weather? Warm and saturated air with moisture should be removed anyway, right?
Is there a minimum supply temperature that should be maintained?
Apart from the “special program,” what else could be causing this?
Thank you all.
On July 12th, we had 7 cm (3 inches) of cement screed installed throughout the entire house.
Since there was no rush, we only started the heating program on September 24th. So the screed had actually been drying for about 11 weeks.
The majority of the water should be out by now; the floor coverings are next, which is why the hot air blower was turned on.
We heated according to the "program" provided by my heating technician, in coordination with the screed installer, until October 11th. I understand this is not the usual "standard program," which I personally think is preferable, since no new build needs a 55-degree Celsius (131°F) supply temperature nowadays. The screed will never see that with our heat pump. The maximum supply temperature according to calculations is 35 degrees Celsius (95°F).
Our heating schedule was as follows:
1: 30°C (86°F)
2: 35°C (95°F)
3-5: 45°C (113°F) (so the screed experienced a higher temperature)
6-12: 35°C (95°F)
13-17: 40°C (104°F) (after the first quick test, it was still too damp, so the supply temperature was raised again)
18: 35°C (95°F)
19: 30°C (86°F)
But hopefully, that’s not the main issue. I am still puzzled that after such a long time, my tiler still finds a CM (calcium carbide) moisture test unnecessary because his moisture meter (from GANN) still shows 65 digits. I understand the intention behind preliminary testing, but I don’t understand why everything still seems so damp?
Yes, I ventilate 3-4 times daily with cross-ventilation. I have two hygrometers in the house, and I ventilate as long as the humidity inside decreases, which is usually around 10 minutes. I do not want to connect multiple industrial dehumidifiers to the hot air blower because that would drive the cost through the roof.
My questions:
Should I keep the windows tilted open in principle? Even at night? Or keep them tilted open plus ventilate quickly during the day and close them at night? Or only ventilate quickly?
Should I avoid ventilation altogether in rainy weather? Warm and saturated air with moisture should be removed anyway, right?
Is there a minimum supply temperature that should be maintained?
Apart from the “special program,” what else could be causing this?
Thank you all.
J
joschua_8514 Oct 2022 20:47Thank you @KlaRa for your detailed feedback.
I don’t want to offend my tiler, he has quite a few years of experience, and he said that based on his experience, with his measuring device, usually anything over 60 digits does not reach the 1.8% residual moisture? which I believe is required for cement screed.
It’s not very critical if just a few thousandths are missing when laying tiles. For parquet flooring, he would of course be more precise. But as mentioned, the screed could still cure for a few more weeks.
As stated at the beginning, since the screed was installed, there have been 2 hygrometers placed around the house.
Last week, both hygrometers mostly showed readings between 20%-30%. One of the devices even recorded 14% air humidity below the minimum. So since our "special program" has been running, the indoor humidity has not been above 40% unless I’m mistaken. But as said, we generally stayed below 30%, at the latest when airing out the house.
I have to add though that the painters were in the house this week, just finished today, and currently it is about 55% humidity. But I don’t think this will affect the screed now. Of course, it will affect the accuracy of your measurement. That’s why I’m giving the readings from last week!
I am thinking of keeping the ventilation running until Sunday evening and then scheduling the CM measurement on Monday. Or is that unnecessary based on the data?
I won’t be charged for the measurement anyway. He just doesn’t want to “bash” the screed, that’s it.
I look forward to your feedback.
Thank you.
I don’t want to offend my tiler, he has quite a few years of experience, and he said that based on his experience, with his measuring device, usually anything over 60 digits does not reach the 1.8% residual moisture? which I believe is required for cement screed.
It’s not very critical if just a few thousandths are missing when laying tiles. For parquet flooring, he would of course be more precise. But as mentioned, the screed could still cure for a few more weeks.
As stated at the beginning, since the screed was installed, there have been 2 hygrometers placed around the house.
Last week, both hygrometers mostly showed readings between 20%-30%. One of the devices even recorded 14% air humidity below the minimum. So since our "special program" has been running, the indoor humidity has not been above 40% unless I’m mistaken. But as said, we generally stayed below 30%, at the latest when airing out the house.
I have to add though that the painters were in the house this week, just finished today, and currently it is about 55% humidity. But I don’t think this will affect the screed now. Of course, it will affect the accuracy of your measurement. That’s why I’m giving the readings from last week!
I am thinking of keeping the ventilation running until Sunday evening and then scheduling the CM measurement on Monday. Or is that unnecessary based on the data?
I won’t be charged for the measurement anyway. He just doesn’t want to “bash” the screed, that’s it.
I look forward to your feedback.
Thank you.
Let’s start with the last point: the tile installer does not want to "beat down" the screed.
That’s completely unfounded; you cannot "beat down" a screed.
If 10 measurements are required, 10 correspondingly small test openings must be made, which should be sealed again with a quick-setting mortar before the floor covering work begins.
Experience aside, if the hygrometer shows a validated value below 50%, the screed or other mineral-based components no longer release moisture into the indoor air. You should, however, hold the hygrometer (taking your own safety into account, of course) in the steam of a pot of boiling water. After about 5 minutes, it should show a value well above 90%.
Beforehand (!), place the hygrometer in the refrigerator for about 2 hours. The value should be around 10%.
This is a kind of "quick calibration" to check whether the values displayed on the device’s scale are approximately correct.
---------------
When the floor installer performs the CM (calcium carbide) test, please make sure to document the following parameters:
a) Depth of the test opening in cm
b) Sample weight in g (for cement screeds, this should be between 20g and a maximum of 50g)
c) Whether the installer handled the sample with their fingers during collection
d) Duration of the measurement inside the pressure vessel
e) Whether the sample or pressure vessel was gently shaken during the measurement phase
f) The manometer reading in bar
g) The CM residual moisture value recorded by the tile installer as the final value
--------------------------
These details are important!!
Simply writing down a value, for example, 1.8%, is by no means sufficient for documentation!!
Ultimately, a brief note in the measurement report (to be created by the floor installer and handed over to the client) should indicate exactly where the measurement spot was located.
Not as simple as it might seem.
Let’s hope the fuss was unnecessary, that you hired a qualified professional, and that the trade "Tiling and slab work" remains free of defects in the long term!
Best regards: KlaRa
That’s completely unfounded; you cannot "beat down" a screed.
If 10 measurements are required, 10 correspondingly small test openings must be made, which should be sealed again with a quick-setting mortar before the floor covering work begins.
Experience aside, if the hygrometer shows a validated value below 50%, the screed or other mineral-based components no longer release moisture into the indoor air. You should, however, hold the hygrometer (taking your own safety into account, of course) in the steam of a pot of boiling water. After about 5 minutes, it should show a value well above 90%.
Beforehand (!), place the hygrometer in the refrigerator for about 2 hours. The value should be around 10%.
This is a kind of "quick calibration" to check whether the values displayed on the device’s scale are approximately correct.
---------------
When the floor installer performs the CM (calcium carbide) test, please make sure to document the following parameters:
a) Depth of the test opening in cm
b) Sample weight in g (for cement screeds, this should be between 20g and a maximum of 50g)
c) Whether the installer handled the sample with their fingers during collection
d) Duration of the measurement inside the pressure vessel
e) Whether the sample or pressure vessel was gently shaken during the measurement phase
f) The manometer reading in bar
g) The CM residual moisture value recorded by the tile installer as the final value
--------------------------
These details are important!!
Simply writing down a value, for example, 1.8%, is by no means sufficient for documentation!!
Ultimately, a brief note in the measurement report (to be created by the floor installer and handed over to the client) should indicate exactly where the measurement spot was located.
Not as simple as it might seem.
Let’s hope the fuss was unnecessary, that you hired a qualified professional, and that the trade "Tiling and slab work" remains free of defects in the long term!
Best regards: KlaRa
J
joschua_8515 Oct 2022 16:31Thank you for the detailed response, but I think the humidity is still too high anyway because of the painter… although last night it was already down to 49%. I will probably test it tomorrow. CM measurement has already been arranged.
J
joschua_8519 Oct 2022 21:24So, a quick update. We conducted the CM (Calcium Carbide) measurement today, even though the GANN meter still showed almost everywhere above 60 digits. The CM measurement finally showed 1.9. Tomorrow, I will pick up my tiles, and work starts on Friday.
He followed all the steps as described by @KlaRa. Using a spoon, 50 grams (1.8 oz) were taken from the cross-section of the screed, shaken for 2 minutes, waited for 5 minutes, then shaken again for 1 minute—resulting in 1.9; done.
He followed all the steps as described by @KlaRa. Using a spoon, 50 grams (1.8 oz) were taken from the cross-section of the screed, shaken for 2 minutes, waited for 5 minutes, then shaken again for 1 minute—resulting in 1.9; done.
Similar topics