# Cracking cornerbead



## Northern Taper (Dec 5, 2017)

Hi Fellows. I am new to this forum, and have a question for you all. I have been using synko mud for many years, but have had a issue on my last job. I had a situation where I have a 45 degree bullnose cornerbead on a 30 degree angle outside corner. When I went to coat it of course the mud application is a little thicker than normal. Well the next day we come back there is a crack along about half the corner bead. So I v out the cracks and fill them but the next day there are cracks again. I have been filling these type of corner like this for 10 years. So the next thing I try is veeing out the cracks and filling them with 20 min hot mud. Everything goes fine, we prime the surface with level 5 primer, then put on the first coat of finish paint. Come back the next day and the cracks are back. Do you have any ideas that's wrong?


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## Mr.Brightstar (Dec 2, 2011)

Movement would be my first guess. 


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## Northern Taper (Dec 5, 2017)

I don't think its movement, but I have learnt to never say never . We finally removed a good part of the finishing mud within a 1.5" of the corner, then filled it with 2 coats of 20 min hot mud. Then skimmed it with finishing and it actually didn't crack. But it still perplexes me. Have any of you had a back batch of mud? Frozen???


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## Mr.Brightstar (Dec 2, 2011)

Sounds like you got solid results. 


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## endo_alley_revisited (Aug 9, 2016)

Northern Taper said:


> Hi Fellows. I am new to this forum, and have a question for you all. I have been using synko mud for many years, but have had a issue on my last job. I had a situation where I have a 45 degree bullnose cornerbead on a 30 degree angle outside corner. When I went to coat it of course the mud application is a little thicker than normal. Well the next day we come back there is a crack along about half the corner bead. So I v out the cracks and fill them but the next day there are cracks again. I have been filling these type of corner like this for 10 years. So the next thing I try is veeing out the cracks and filling them with 20 min hot mud. Everything goes fine, we prime the surface with level 5 primer, then put on the first coat of finish paint. Come back the next day and the cracks are back. Do you have any ideas that's wrong?[/QUOTE
> 
> When you say 45 degree bullnose on 30 degree corner, wth is that? Did you properly prebend the bastard angle bead to match the corner angle? Maybe this should have been hand formed. Sounds like your mud was too thick in depth. It surface dried before the inside mud had a chance to dry. When the inside finally began to shrink, it cracked the dry outside mud. Sounds like operator error to me. I probably would not blame the mud.


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## Mark in Montreal (Aug 29, 2016)

Agree with last post. Bulk fill should have been hot to start with.


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## SamHel64 (Jan 7, 2018)

I agree with Mark and Endo

Sam Hel
http://www.buttetowing.com/helena-mt.html


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## Finire (Feb 21, 2018)

Like others have basically said... premixed mud doesn't provide structural strength like hot mud.


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## hendrix417 (Aug 9, 2018)

usg handbook says,, 'attachment no less than 8 inches apart..'


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