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Posted: 6/27/2002 7:02:09 AM EDT
ust put in a new piece of drywall for my father-in-law to patch a hole around his AC intake. The mud had to be applied fairly thick to match up what was their before. The first coat of mud I put on cracked [b]badly[/b] when it dried. My question is why did the mud crack? The mud I used had been thinned with water (the last job I did was a ceiling & I thinned it so it would be easer to spread) did it crack because of a thick coat of thinned mud or is their something else I'm not seeing? echo6
Link Posted: 6/27/2002 7:14:41 AM EDT
It cracked because you put too much on at one go. As drywall mud dries it shrinks.....a nomral small layer does not shrink enough to crack but a thick layer does. So just like a mudpuddle it cracked when its surface area was too large. The best way is to put on MULITPLE coats and let each one dry...sand in between.
Link Posted: 6/27/2002 7:18:34 AM EDT
Originally Posted By Stormbringer: The best way is to put on MULITPLE coats and let each one dry...sand in between.
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Strombringer is correct. I usually do about 4 coats or so on places out in the open like the living room or kitchen. Keving67
Link Posted: 6/27/2002 7:20:48 AM EDT
If you want to lay the mud on thickly, use a setting type joint compound. That's the kind that comes in a bag and is mixed with water on the job. The kind that comes "ready-mixed" in the pail or a cardboard box is a drying type compound and will shrink and crack when applied in thick fills. The setting type is closer to a high strength plaster. It's generally harder to sand unless you get the kind using perlite as the aggregate.
Link Posted: 6/27/2002 7:22:11 AM EDT
You guys are awesome; this place really is the "be-all, know-all repository of knowledge " Should I sand off all the cracked areas or just sand the mud smooth, and recoat it? Thanks again, Echo6
Link Posted: 6/27/2002 7:38:51 AM EDT
sand until cracks are gone, then build it up do not thin joint compound unless spraying it for texture...
Link Posted: 6/27/2002 9:42:35 AM EDT
Nice to know we got drywall people around here, as we are finishing our downstairs.. just got the drywall delivered yesterday. I'm currently finishing up some recessed lighting and some speaker wire for the surround sound.. then it's drywall time!! I sure hope I know what I'm doing!
Link Posted: 6/27/2002 9:53:24 AM EDT
ShamusMcOI is a drywall guy....
Link Posted: 6/27/2002 9:56:02 AM EDT
SNorman, Just remember this mantra...."less is better"...you can always add coats, but to sand is a time waste. When sanding you should only be running the pole sander lightly over all areas that need it just to take off the light ridges from knife work. Oh..and use paper tape, not mesh, mesh is for setting type and patches. The paper tape is to be used with general purp. mud as it has a higher concentration of naturally occuring "glue" and makes the resulting joints much stronger when bonded to the paper of the "rock". Good luck, and remember if you look like the Pillsbury Dough Boy when sanding then you have used too much mud. ;)
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