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-   -   Parging - Need help (http://www.diychatroom.com/f105/parging-need-help-163050/)

TomU 11-12-2012 08:55 AM

Parging - Need help
 
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I attempted to parge my cold storage room, which right now is ugly poured concrete. The house was built two years ago, so the concrete is in pretty good shape. I haven't observed any moisture issues.

Here's what I did: I broomed off the wall, hammered off some parts that were sticking out too much. Then I got some "Type S" mason mix, mixed it with water until it was a peanut butter like consistency. Then I sponged/sprayed the wall until it was damp, but not wet. I troweled it 1/4" or so onto the wall, working it until it was fairly smooth. Then I waited a bit until it hardened, and I used a sponge to scrub it smooth.

When I came back half an hour later (or so) I noticed several cracks had developed. I checked them, and it looked like the coat had detached from the concrete wall. So I removed it all, because obviously I didn't do it right.

What did I do wrong? I can't seem to find enough information on how to do it properly. Was my mix not wet enough? Was brooming off the wall and removing lose dirt not sufficient? Should I have done a "slurry coat", or should I have used some adhesive on the wall (if so, what would I look for in a typical home improvement store?)? Did I use the wrong trowel? Did I work it too much by trying to smooth it out right away?

I appreciate any help.

TomU 11-14-2012 08:49 PM

Does nobody have any advice for me?

mikegp 11-15-2012 07:46 AM

Interested in an answer as well. I'd like to this or something similar to a basement wall that can't be framed.

stuart45 11-15-2012 11:00 AM

If I was doing the job I would give the concrete a coat of 3/1 water/PVA first and wait till it was tacky.
Then give it a scratch coat of 1/1/4 lime/OPC/sand.
Then a top coat of 1/1/5 lime/OPC/sand. Use plastering sand as there is less shrinkage.

Tscarborough 11-15-2012 01:25 PM

You can use a bonding agent alone (make sure it is a re-emulsifiable bonding agent) painted on the wall, you can use a slurry as mentioned above (but have to work fast or it will become a bond breaker), or add bonding agent to the mix. At 1/4" thick, you are pulling it off the wall when you work it with the trowel, so aim for 3/8" and just get it spread out don't over work it. The cracks are shrinkage cracks from too much moisture in the plaster, probably from wetting the wall.

TomU 11-15-2012 01:40 PM

Quote:

Originally Posted by Tscarborough (Post 1052864)
You can use a bonding agent alone (make sure it is a re-emulsifiable bonding agent) painted on the wall, you can use a slurry as mentioned above (but have to work fast or it will become a bond breaker), or add bonding agent to the mix. At 1/4" thick, you are pulling it off the wall when you work it with the trowel, so aim for 3/8" and just get it spread out don't over work it.

Thanks for the tips. I think my mistake was that I put on too much and overworked by trying to make it the final coat right away. I'm also thinking that the mix was maybe too dry.

Quote:

Originally Posted by Tscarborough (Post 1052864)
The cracks are shrinkage cracks from too much moisture in the plaster, probably from wetting the wall.

I don't think they were shrinkage cracks because these areas were completely detached from the concrete wall behind it.

I'll get a wire brush to try and roughen the surface a bit and then I'll try a slurry coat, followed by a thinner base coat. Then I'll wait until the base coat is hardening and scratch it horizontally. Then wait a day or two before putting on the final coat. When putting on the final coat, same consistency as the base coat? And wait until it hardened a bit before working it with a trowel and sponge?


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