ᐅ Plaster facade with external thermal insulation composite system (ETICS) using mineral wool – brown stains
Created on: 13 Feb 2023 21:27
W
wp.seeker
Hello everyone,
Our house was insulated and plastered between early and mid-November 2022.
The insulation is Rockwool Coverrock II, followed by a base coat, reinforcing mesh, top coat, and facade paint.
About two weeks later, brown spots appeared in various places, irregularly distributed on all sides of the facade. There are small spots and larger spots up to about 10cm (4 inches) in diameter, some pale, some intense brown-red. Over the course of 2–3 weeks, more spots showed up, but now no new ones seem to be appearing.
Has anyone had experience with this?
An online search suggested it could be moisture penetration dissolving the binding agents and fillers, or phenolic resin residues, resin pockets in the mineral wool boards themselves somehow coming through.
During the facade work, there were a few brief rain showers, so it’s possible the mineral wool got wet.
However, against the moisture penetration theory is that some spots appeared directly under the eaves, places that couldn’t have been exposed to rain, or on areas that were only installed after the rain. Overall, we had a very favorable weather window for that time of year.
The very irregular appearance could support the phenolic resin residue or resin pocket explanation. As far as we can tell, it’s not related to the board edges or possible fixing points.
Has anyone observed this phenomenon before and how was it resolved?
Thank you very much
Our house was insulated and plastered between early and mid-November 2022.
The insulation is Rockwool Coverrock II, followed by a base coat, reinforcing mesh, top coat, and facade paint.
About two weeks later, brown spots appeared in various places, irregularly distributed on all sides of the facade. There are small spots and larger spots up to about 10cm (4 inches) in diameter, some pale, some intense brown-red. Over the course of 2–3 weeks, more spots showed up, but now no new ones seem to be appearing.
Has anyone had experience with this?
An online search suggested it could be moisture penetration dissolving the binding agents and fillers, or phenolic resin residues, resin pockets in the mineral wool boards themselves somehow coming through.
During the facade work, there were a few brief rain showers, so it’s possible the mineral wool got wet.
However, against the moisture penetration theory is that some spots appeared directly under the eaves, places that couldn’t have been exposed to rain, or on areas that were only installed after the rain. Overall, we had a very favorable weather window for that time of year.
The very irregular appearance could support the phenolic resin residue or resin pocket explanation. As far as we can tell, it’s not related to the board edges or possible fixing points.
Has anyone observed this phenomenon before and how was it resolved?
Thank you very much
HausiKlausi13 Feb 2023 21:59Right at the beginning, the question: Someone must have insulated/plastered this, right? What does that person say? I would consider this a defect and first ask those responsible about it. (Apart from that, drilling at an inconspicuous spot could provide more clarity, but of course not BEFORE the step described above.)
The facade contractor is at a loss and claims to have done everything correctly.
The mineral wool manufacturer states that the stains will disappear after one to two years (according to the facade contractor who spoke with them).
The site management remains reserved, as they are paid by the building owner.
The energy consultant/construction supervisor has not seen anything like this before and believes that the entire facade should be treated with some kind of separation layer and repainted—not just the individual stains as the mineral wool manufacturer suggests, but the entire surface.
There is also a meeting planned with all parties involved, but they might all give us excuses; everyone wants to avoid responsibility. That is why I am asking here for any experiences.
The mineral wool manufacturer states that the stains will disappear after one to two years (according to the facade contractor who spoke with them).
The site management remains reserved, as they are paid by the building owner.
The energy consultant/construction supervisor has not seen anything like this before and believes that the entire facade should be treated with some kind of separation layer and repainted—not just the individual stains as the mineral wool manufacturer suggests, but the entire surface.
There is also a meeting planned with all parties involved, but they might all give us excuses; everyone wants to avoid responsibility. That is why I am asking here for any experiences.
B
Bausparfuchs13 Feb 2023 22:13Based on my amateur understanding, I don’t think the insulation is the cause of the stains.
It looks more like contamination within the plaster itself. To be certain, you would probably need to open up the wall structure.
If it were coming from the insulation, the stains would likely cover a larger area.
As I said, it appears to be foreign substances in the plaster or even in the paint itself.
What can be done? Find the cause and repaint completely, of course. This kind of issue is not attractive.
It looks more like contamination within the plaster itself. To be certain, you would probably need to open up the wall structure.
If it were coming from the insulation, the stains would likely cover a larger area.
As I said, it appears to be foreign substances in the plaster or even in the paint itself.
What can be done? Find the cause and repaint completely, of course. This kind of issue is not attractive.
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