Advice from render experts! Rust?

DAR21

New Member
Hi All,

I had a small development project (house conversion into flats) done three years ago. At the time I had contracted all works out. My builder recommended a mosaic plaster and we went with Ceresit C77 mosaic render as the top coat on exterior. The finished job looked brilliant.

Three years on, the side of the property is now covered in rust marks. We are on a very busy main road which could have played a role. Can anyone advise what could have caused this? Would something like a k-pro or Paraguard helped? Not sure if that can be used ontop of these mosaic renders.

I purchased a new family home and we are redoing the external render which is currently a horrible green so keen to get it right this time and avoid the mosaic render (although we love this look) if this is likely due to the product itself.

Thanks in advance.
20200628_112810.jpg
 

yanto

New Member
Some drydashing chips are prone to rusting on the wall. I wonder if there's been a bit of contamination while mixing
 

bobski

Well-Known Member
Could be in the mix (mosaic bucket coat), I would have thought it would be more regular if that was the case (factory problem).
It might be through the application, could be a rusty/s**t tool they stirred it or applied with.

For the amount you have there (20 odd?), I'd pick them out to not cause further agg, and touch in.
 

The Hobo

Well-Known Member
Hi All,

I had a small development project (house conversion into flats) done three years ago. At the time I had contracted all works out. My builder recommended a mosaic plaster and we went with Ceresit C77 mosaic render as the top coat on exterior. The finished job looked brilliant.

Three years on, the side of the property is now covered in rust marks. We are on a very busy main road which could have played a role. Can anyone advise what could have caused this? Would something like a k-pro or Paraguard helped? Not sure if that can be used ontop of these mosaic renders.

I purchased a new family home and we are redoing the external render which is currently a horrible green so keen to get it right this time and avoid the mosaic render (although we love this look) if this is likely due to the product itself.

Thanks in advance.View attachment 50958
cut out one bleeder to see what the cause is
 
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