MeTheBuilder15 Jun 2022 18:08Hello forum,
In our newly built house from 2018, which we had built as a turnkey project, there is unfortunately a recurring mold problem on the wooden ceiling of the masonry utility room.
This approximately 9 m2 (97 square feet) extension to our residential building has a cavity wall (sand-lime brick and facing brick), but it is not insulated and is unheated. It has a flat roof made of a wooden structure and bitumen membrane. The roof is also not insulated. We store garden tools and bicycles in this room. For ventilation, the construction company installed two core-drilled holes with a diameter of DN100 (about 4 inches) in opposite walls (one near the top and one near the bottom). There are rust covers with insect screens in front of the openings. The room also has a window, but it remains closed at all times.
Unfortunately, moisture forms under the roof battens during the cold season. After the first winter, mold was clearly visible between the purlins. I initially attributed this to residual construction moisture. The problem recurred in the second winter. When everything had dried out in the summer, I removed the mold both mechanically and chemically and then applied a wood stain. However, in the third winter, I had to realize that my measures did not help. Mold formed again.
I contacted the construction company and asked whether this is a fundamental design issue and if improvements are needed. Our former site manager said that this is state of the art and that we should protect the room from cooling by using an electric heater. However, I really do not want to heat a utility room used for garden stuff.
In the fourth winter, I installed a bathroom fan with humidity control in the ventilation duct. It ran almost continuously because the humidity was so high. Mold was perhaps somewhat less severe that winter, but it was still present.
So something clearly needs to be done. A friend of mine who is a roofer said he would install an external roof insulation. To me, that sounds like a construction defect. What do you think? What are your technical suggestions? Is this a construction defect in your opinion? How would you approach the construction company?
Thank you very much for any input.
In our newly built house from 2018, which we had built as a turnkey project, there is unfortunately a recurring mold problem on the wooden ceiling of the masonry utility room.
This approximately 9 m2 (97 square feet) extension to our residential building has a cavity wall (sand-lime brick and facing brick), but it is not insulated and is unheated. It has a flat roof made of a wooden structure and bitumen membrane. The roof is also not insulated. We store garden tools and bicycles in this room. For ventilation, the construction company installed two core-drilled holes with a diameter of DN100 (about 4 inches) in opposite walls (one near the top and one near the bottom). There are rust covers with insect screens in front of the openings. The room also has a window, but it remains closed at all times.
Unfortunately, moisture forms under the roof battens during the cold season. After the first winter, mold was clearly visible between the purlins. I initially attributed this to residual construction moisture. The problem recurred in the second winter. When everything had dried out in the summer, I removed the mold both mechanically and chemically and then applied a wood stain. However, in the third winter, I had to realize that my measures did not help. Mold formed again.
I contacted the construction company and asked whether this is a fundamental design issue and if improvements are needed. Our former site manager said that this is state of the art and that we should protect the room from cooling by using an electric heater. However, I really do not want to heat a utility room used for garden stuff.
In the fourth winter, I installed a bathroom fan with humidity control in the ventilation duct. It ran almost continuously because the humidity was so high. Mold was perhaps somewhat less severe that winter, but it was still present.
So something clearly needs to be done. A friend of mine who is a roofer said he would install an external roof insulation. To me, that sounds like a construction defect. What do you think? What are your technical suggestions? Is this a construction defect in your opinion? How would you approach the construction company?
Thank you very much for any input.
MeTheBuilder15 Jun 2022 18:26I can only imagine air as the source of the moisture. The roof cools down quickly at night. The air inside the room condenses on the now cold roof. There is nothing in the room that could release moisture. At most, some fertilizer residues, but they are stored in sealed bags.
W
WilderSueden15 Jun 2022 22:00Do you use the bicycles in bad weather as well? For me, that would definitely be a significant source of moisture.
Would it be possible to install a small fan in the holes to ensure good air circulation? My suspicion is that the ventilation might not be as effective as expected, for example, because the area is relatively sheltered from the wind.
Would it be possible to install a small fan in the holes to ensure good air circulation? My suspicion is that the ventilation might not be as effective as expected, for example, because the area is relatively sheltered from the wind.
bauenmk202016 Jun 2022 09:36You could also plaster the interior walls with lime plaster to help regulate humidity. Otherwise, I would recommend keeping the window slightly open more often (when the weather is dry). It’s not ideal that the upper core drilling is located next to the window. Depending on the situation (if the window is open) and if the exhaust vent is installed in this core drilling, you might end up with a “ventilation short circuit” here.
If the flat roof is still in that condition, insulation should be added. There are insulation boards available with built-in slopes that can be installed in sections. Your friend can probably advise you further, and I would discuss the next steps with them.
The question about the floor is also reasonable. What is its composition or construction?
If the flat roof is still in that condition, insulation should be added. There are insulation boards available with built-in slopes that can be installed in sections. Your friend can probably advise you further, and I would discuss the next steps with them.
The question about the floor is also reasonable. What is its composition or construction?
MeTheBuilder16 Jun 2022 11:41WilderSueden schrieb:
Do you use the bicycles in bad weather as well? For me, that would definitely be a significant source of moisture. No, we hardly use the bicycles at all, but that’s another story. 😀
I have already installed a fan in the upper core drill hole. In my opinion, it’s quite noisy. The problem might also be that air can get trapped between the rafters. I could cover the rafters with boards or panels, but then I’m concerned that I would just be hiding the mold.
bauenmk2020 schrieb:
If the flat roof is still in that condition, then insulation needs to be added. There are insulation boards with pre-formed slopes that can be installed in sections. But your acquaintance can probably help you with this, and I would discuss the next steps with them! Yes, the roof is still in that condition. The question is whether I can prove a defect to the construction company. In my opinion, that is the case. We are still within the 5-year warranty period. So far, I haven’t been able to prevent mold in this room, despite proper use and technical aids (fan). My acquaintance might be able to help me, but it won't be free...
bauenmk2020 schrieb:
The question about the floor is also justified. What is its construction? There is a screed laid, with the same setup as in the rest of the house. It is dry and looks in good condition.
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