ᐅ Mold? – Removing stains in the stairwell and identifying possible causes
Created on: 31 Jan 2023 12:09
A
abc12345Hello everyone,
A few years ago, during the renovation of the living spaces, we removed the wallpaper in our stairwell and now plan to replaster it. We have noticed that one wall (an exterior wall) in the stairwell has black spots. As a layperson, I would suspect mold.
My question is whether I should completely remove the damaged plaster down to the masonry, or if it might be sufficient to just remove the surface layer?
I am wondering how mold could form there. It only appears on this one wall and nowhere else in the entire three-story stairwell. Out of curiosity, I placed a hygrometer there. We do not heat the stairwell (there is currently no radiator and none planned, although the installation provision exists), and the temperature is around 12–13°C (54–55°F) with a relative humidity fluctuating between 65 and 68 percent.
The facade is intact and was recently repainted by a professional. There are no cracks or other damage that might allow moisture to penetrate from outside to inside.
Thank you for your feedback.
A few years ago, during the renovation of the living spaces, we removed the wallpaper in our stairwell and now plan to replaster it. We have noticed that one wall (an exterior wall) in the stairwell has black spots. As a layperson, I would suspect mold.
My question is whether I should completely remove the damaged plaster down to the masonry, or if it might be sufficient to just remove the surface layer?
I am wondering how mold could form there. It only appears on this one wall and nowhere else in the entire three-story stairwell. Out of curiosity, I placed a hygrometer there. We do not heat the stairwell (there is currently no radiator and none planned, although the installation provision exists), and the temperature is around 12–13°C (54–55°F) with a relative humidity fluctuating between 65 and 68 percent.
The facade is intact and was recently repainted by a professional. There are no cracks or other damage that might allow moisture to penetrate from outside to inside.
Thank you for your feedback.
Too Cold and Too Damp
13 degrees Celsius (55°F) and 60% humidity would already be quite damp, I believe, according to the chart, especially at 20 degrees Celsius (68°F).
Should I put in a small dehumidifier with a heater?
I once read(!) that the risk of mold decreases starting at around 16 degrees Celsius (61°F).
13 degrees Celsius (55°F) and 60% humidity would already be quite damp, I believe, according to the chart, especially at 20 degrees Celsius (68°F).
Should I put in a small dehumidifier with a heater?
I once read(!) that the risk of mold decreases starting at around 16 degrees Celsius (61°F).
W
WilderSueden31 Jan 2023 13:10The crucial factor is less the air temperature and more the surface temperature of the wall, as well as the dew point (which is calculated from air temperature and humidity). Do you have an infrared thermometer to measure the wall?
You can see that the mold is mainly in the corner. Are these two exterior walls? Then you have a geometric thermal bridge, plus limited air circulation due to the corner.
You can see that the mold is mainly in the corner. Are these two exterior walls? Then you have a geometric thermal bridge, plus limited air circulation due to the corner.
Thank you for your initial feedback. The house was built in 1965, and the stairwell has always been cold because there has never been any heating installed there, which is why the mold development surprises me. The exterior wall hasn’t been altered except for a single repaint.
Unfortunately, I don’t have an infrared thermometer to measure the wall temperature, but I can think of an acquaintance who has one.
Yes, exactly, the mold in the corners is on two exterior walls.
What is the best approach to take BEFORE replastering the stairwell, and what can I do AFTER completion to ensure that the mold problem is fully resolved?
Unfortunately, I don’t have an infrared thermometer to measure the wall temperature, but I can think of an acquaintance who has one.
Yes, exactly, the mold in the corners is on two exterior walls.
What is the best approach to take BEFORE replastering the stairwell, and what can I do AFTER completion to ensure that the mold problem is fully resolved?
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