ᐅ Ceiling Penetration Condensation in Drainage Pipe

Hello,

I hope I'm in the right subforum and that you might be able to help me.

In our house, there is a ceiling opening from the upper floor to the ground floor in an outer corner. The main bathroom is on the upper floor, and the utility room is on the ground floor.

The wastewater pipe from the bathtub and the toilet runs through this opening. Additionally, there is a flexible pipe for a potential future photovoltaic system. The opening is sealed with what I believe is gypsum and painted white in the usual way.

In September, we first noticed water accumulating in the floor of the utility room. This comes through the ceiling opening and runs down the pipe.

Since the house is still under warranty (new house), condensation water was suspected. The roof (hip roof), bathroom, and pipes in the attic were inspected — everything was dry except for the utility room.

By now, the area with the "gypsum" has become really soft and is starting to develop mold. The assumption is that moisture-laden air is reaching this spot, passes through the gypsum (thermal bridge), comes down, and is pushed from above.

Therefore, today the gypsum was completely removed and the area lined with insulation wool. This reportedly helped in another house.

Coincidentally, today I had a client at my company who runs a plumbing business.

He said that using insulation wool is generally the right approach. However, he would mix Rotband (gypsum plaster) with a product called Fit and re-plaster the area. Fit to make the plaster no longer vapor-permeable. He would do this to prevent moisture from reaching the insulation wool in the first place.

What do you think? What can be done? If the insulation wool helps, that is already good. But it also looks quite bad, because now you can see the insulation wool in the ceiling.

Attached are some pictures, first from the bathroom above the utility room, then from the utility room itself, showing the pipe…

Thank you very much for your help

I don’t understand why the pipe should be cold at exactly this spot. After all, it is all within the thermal envelope of the house.

Because the drainpipe is located there. It also serves as the exhaust pipe for the bathroom upstairs. Additionally, a flexible empty conduit runs there for a possible photovoltaic system.

Yesterday, I noticed water running down behind this insulation. I then completely removed it. It was dry at the bottom and wet at the top.

The fact is that water is accumulating up there. Whether it comes from the utility room and condenses there or from somewhere else, I cannot determine.

Coletrickle_7808 schrieb:

Because the downpipe is located there. It also serves as the exhaust pipe for the bathroom on the upper floor. Additionally, a flexible empty conduit runs there for a potential photovoltaic system.

Yesterday, I noticed water running behind this insulation. I completely removed it. The bottom part was dry, the top was wet.

The fact is that water is forming up there. Whether it is coming from the utility room and condensing there or from somewhere else, I cannot say.

Do you mean ventilation for the waste pipe? (It’s usually called venting, but ventilation is meant; it’s necessary to prevent negative pressure caused by water flowing down the pipe.)

Then cold air from outside can also enter there. So the pipe is cold (due to outside air), and warmer, more humid air is around it = condensation.

What exactly do you mean by a prepared conduit for photovoltaics? Does it also run through the roof membrane? Is it sealed or accidentally left open?

I mean the ventilation. However, the pipe is insulated up to the first T-joint (toilet inlet) (see first picture).

I believe the flexible conduit runs up to the attic (cold roof).

From Sunday to Monday, I blocked everything with toilet paper and sealed the opening with foil. Then I removed it yesterday evening. The paper was completely damp, almost soaked through.

So it seems the water is running off the roof after all?
I don’t fully understand the situation... You recently built (or had it built), right?
Who is responsible? Contact them, this is definitely an issue or defect that needs to be fixed.