Hello 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.
bauenmk202016 Jun 2022 12:10MeTheBuilder schrieb:
Yes, the roof is still in this condition. The question is whether I can prove a defect to the construction company. In my opinion, this 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 (ventilators). A friend of mine might be able to help, but he won’t do it for free... Does the roof have a slope, and does it drain sufficiently into your internal drainage system? Does water possibly remain standing?
It should also be clarified whether the roof has been fully completed. There is a flat roof guideline you might refer to for orientation. You can also search for "Bauder" as a reference.
Do you have a moisture meter? I would use it to measure the remaining moisture content in the individual building components. Additionally, you could set up a humidity/temperature sensor and possibly log the data.
MeTheBuilder16 Jun 2022 13:06bauenmk2020 schrieb:
Does the roof have a slope, and does it drain sufficiently into your internal drainage system? Does any water remain standing at all?Yes, there is a slope and no water remains standing.bauenmk2020 schrieb:
You could also try searching for "Bauder."I just did. Our structure basically follows what they recommend for carports. My carport doesn’t have any mold either. 😀bauenmk2020 schrieb:
Do you have a moisture meter?Unfortunately, no. The fan has a control unit with a display. The sensor is installed directly under the battens. The control is set to switch on at 70%. In winter, readings were often well above 80%. The fan ran almost continuously. At this time of year, the 70% level is no longer reached.At first, I thought the water was leaking from above... but these are actually residues from the glazing work 🙄 you could have at least taped off the area and removed the cables from the mounts to prevent everything from getting so “dirty”/“filthy”/“messed up”…
About the problem. Summer is not a good time for analysis. 🙄
In winter, you could have taken immediate action by opening the window wide for a few minutes in the morning and evening.
You can then see the condensation directly on the outside pane. Once the fog clears, close it again after about 5 minutes.
You should also measure the surface temperatures in autumn/winter—ceiling, walls, and floor. The ceiling should be by far the coldest surface…
What are the indoor temperatures in winter/summer? Nearly the same as outdoor temperatures?
The window is probably triple-glazed. That’s too good for a shed. A poorer quality double-glazed window would be better, so you can at least wipe off the condensation on the glass...
(If the roof is the culprit)
About the problem. Summer is not a good time for analysis. 🙄
In winter, you could have taken immediate action by opening the window wide for a few minutes in the morning and evening.
You can then see the condensation directly on the outside pane. Once the fog clears, close it again after about 5 minutes.
You should also measure the surface temperatures in autumn/winter—ceiling, walls, and floor. The ceiling should be by far the coldest surface…
What are the indoor temperatures in winter/summer? Nearly the same as outdoor temperatures?
The window is probably triple-glazed. That’s too good for a shed. A poorer quality double-glazed window would be better, so you can at least wipe off the condensation on the glass...
(If the roof is the culprit)
MeTheBuilder16 Jun 2022 18:56driver55 schrieb:
In winter, you could have directly counteracted by opening the window wide for a few minutes in the morning and evening. That’s not something I want to do long-term, neither in the living area nor in a utility room. In the living area, we have a controlled ventilation system, which works well. For the utility room, I’m looking for another solution...
driver55 schrieb:
What are the indoor temperatures in winter/summer? Almost the same as outside? A bit warmer than outside. We haven’t had frost in there yet.
driver55 schrieb:
The window must be triple-glazed. That’s too good for the shed. For me, the window is almost proof that good insulation can prevent condensation. Unfortunately, that doesn’t work with the flat roof. It’s probably really missing insulation.
Would rafter insulation possibly be a solution? That’s something I could technically manage myself. Although I’m not sure about vapor barriers and so on. Should there be an air gap? Would it maybe still mold there? Adding insulation above the roof deck sounds very reasonable. But that’s technically too much for me. Also, my friend said it might even require rebuilding the wall. 😱
W
WilderSueden16 Jun 2022 20:06MeTheBuilder schrieb:
The problem will also be that the air can become stagnant between the rafters.I have thought about something like that as well. I am familiar with this ventilation concept from material boxes on boat trailers, where many people additionally install solar-powered ventilators to prevent the air inside the box from becoming stagnant. Before covering anything, I would rather try to improve the air circulation throughout the entire space.MeTheBuilder schrieb:
A bit warmer than outside. We haven’t had frost there yet.At 35 degrees Celsius (95°F) outside, it’s 38 degrees Celsius (100°F) in the shed? 🙄As I said, measure the surface temperatures…
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