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-   -   Cracking in painted plaster over cement block wall (http://www.diychatroom.com/f105/cracking-painted-plaster-over-cement-block-wall-181965/)

almoniyot 06-17-2013 05:18 AM

Cracking in painted plaster over cement block wall
 
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Hello everyone from a 1st time poster.

I had bitumen sheets put on my roof to prevent leakage. (note the bitumen cannot be seen as it is underneath the synthetic grass in the middle picture). In order to get a better seal and to prevent water from leaking where the bitumen meets the wall, the contractor chiseled away some plaster and laid the bitumen sheets inside the wall, and then re-filled the wall with plaster. The walls were then painted. After a rainy winter the lower part of the walls that the contractor filled with plaster are now cracking and look to have absorbed water. I am wondering what is causing this cracking... did he use the wrong material? Or is water leaking from the marble on top of the walls (but this does not explain why there are not cracks in the rest of the walls that he didn't touch). Any thoughts would be appreciated as well as suggestions as to the best way to go about fixing this? Please see attached pictures.

tony.g 06-17-2013 04:52 PM

If he'd just stuccoed over the bitumen sheeting, it would be surprising if the plaster hadn't cracked. What's the wall built of? CMUs?

Tscarborough 06-17-2013 10:59 PM

It looks like either there is moisture in the lower part of the wall or it was stuccoed at a different time than the wall. Either way, it appears that there is too much moisture wicking into the wall.

almoniyot 06-18-2013 02:39 AM

Yes the building/wall is built from CMUs, and the bottom of the wall was plastered (sloppily, it just looks like stucco) at a different time than the rest of the building.

What do you mean by "wicking into the wall" ? Any ideas on how to fix this correctly?

tony.g 06-18-2013 08:11 AM

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Quote:

Originally Posted by almoniyot (Post 1203064)

What do you mean by "wicking into the wall" ? Any ideas on how to fix this correctly?

I think he means this. Because the bottom of the plaster is taken down to the level of the 'grass', it will draw up moisture by capillary attraction. As the plaster is relatively thin, and backed by an impervious sheet for the lower few inches, it will always remain wet. Any paint on it will always blister off.

CarpenterSFO 06-18-2013 09:39 AM

Typically one puts a weep screed and other flashing at the bottom of the stucco to separate the stucco from the ground or floor. As for the cracking, most stuccos won't craze and spall like that. What type of "plaster" is it?

And just for what it's worth - you really mean "bituthene", which is a brand name but also has the generic meaning of a composite, black, rubbery roofing or waterproofing membrane. "Bitumen" is a synonym for asphalt or hot tar.

Tscarborough 06-19-2013 12:33 AM

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Basically, it was done wrong. As shown by the line drawn point to point, the thickness of the stucco varies by quite a bit. The lower edge should have used weep screed and terminated 3-4 inches above finished grade, although he did do the flashing more or less correctly.

almoniyot 06-20-2013 05:00 PM

Thank you everyone, Great drawing tony g.


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