HELP?!
All those Keim coating fans .... ideas please?
I am looking at a high profile modern building in Beijing at the moment. Finished about 7-8 years ago, it is quite a large low-rise building with about 40,000 square metres (400,000 square feet) of rendered concrete walls. All with flat rendered parapets. The render was a multiple layer sprayed concrete render, in four different colours (off-white, light grey, mid-grey and black).
There are several problems:
1) The render is cracked and debonding in a few locations, probably due to poor installation originally (hearsay from people who were present on site at the time).
2) There is cracking and delamination occurring along the top edge of the walls, probably due to water penetration and subsequent freeze-thaw, possibly exacerbated by differential thermal movement.
3) There is very bad soiling of the walls, particularly due to run-down soiling from the parapets, where the atmospheric fallout (which is substantial) is washed over the edge during light to medium rain events.
We are proposing to install a metal weathering along the top of all parapets to shed the water away from the wall (projection will be about 30mm or so - any more will be totally unacceptable from an aesthetic viewpoint ... the concept itself is bad enough). However, ultimately we believe that the render will need to be coated in order to bring the appearance back to an acceptable level.
One area was painted with an acrylic latex paint 12 months ago, and this is standing up okay so far, but it is early days yet.
Several years ago some limited trials were done on very small patches with what I believe were Keim coatings plus others. As I do not know which were the Keim coatings, it is difficult to assess their success. However, I don't think they have stood up very well.
My questions for the list (and especially the Keim coating aficionados, since this is not really a histo-presto issue) are:
1) Are Keim coatings going to provide any protection to the render, or are they merely an aesthetic upgrade solution?
2) Are the Keim coatings likely to cover the variation in colour we now have (varies from rain-washed bleached areas, through original, to gypsum/soot stained areas) so as to give an even colour?
3) How durable are the Keim coatings likely to be?
4) How resistant to further soiling are the Keim coatings likely to be?
If these questions should be directed to Keim themselves, please give me a contact address (preferably email) so that I can do so.
I am trying to borrow a digital camera so that I can send a photo to anybody interested enough to want to follow through with this.
Cheers
david
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david west
Arup Facade Engineering
477 Kent Street, Sydney NSW 2000
PO Box Q116, QVB Post Office NSW 1230
Australia
Tel: +61 (2) 9320 9447
Fax: +61 (2) 9320 9321
Mobile: +61 (419) 223 405
Email: [log in to unmask]
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