Replies

1. 
   Jer | Sep 02, 2008 11:54pm | #1

   Prime the brown coat with white shellac first, then bonder (Plasterweld), then white coat.

   Cut away the brown coat so the edges are undercut in order to mechanically hold things in plce.

1. 
   stephen53 | Sep 03, 2008 12:16am | #2

   thanks, Jer

2. 
   DonCanDo | Sep 03, 2008 01:25am | #3

   I don't have any plaster skills so all of my plaster repairs are with joint compound.  If it needs to be a hard finish, I use Durabond which is harder than regular compound, but still not as hard as plaster.  It works well for me and I haven't had any complaints or problems.

1. 
   MSA1 | Sep 03, 2008 02:59am | #4

   I was gonna say the same thing. I've had repairs all the way down to the lath in a few of my houses. The durabond did the trick. The patch I have in mind was done last summer and is still fine.

   It was kinda neat cause the repair was on the ceiling and when we went into the attic you could see how the Durabond acted just like plaster locking on to the lath. 

   Family.....They're always there when they need you.

3. 
   cynwyd | Sep 03, 2008 03:02am | #5

   might consider some metal lath ove the brown coat

1. 
   Yersmay | Sep 03, 2008 06:46am | #6

   It isn't clear if you're filling a crack or if you're plastering an entire wall... The Plasterweld is a good idea... but it sounds like the brown coat was too dry and it sucked the water out of the finish coat before it had a chance to set. It's important to really wet the brown coat down in advance of the finish coat. Trowel the first thin layer of the finish coat over the brown... it should take a preliminary set right away, then go over it again with another thin layer. That, too, should take an initial set really quickly and then you can either fill in the cat's faces if you want a smooth coat, or you can experiment with texture. Whatever you do, a finish coat should be troweled repeatedly to compress it. It's hard to tell you just how much time should go by, but after a while it's good to apply some water and trowel that into the finish plaster... it further consolidates the finish plaster and it keeps it from drying out too soon. However, if you apply water too soon you'll see the finish plaster blister, which is not so good. This will all take some experience to figure out, but you'll get a feel for it. Best of luck!

4. 
   MikeHennessy | Sep 03, 2008 03:16pm | #7

   The cracking is due to the old plaster sucking the water out of the new. As others have indicated, you can minimize this by sealing the old plaster before applying the new. I have also had luck with moistening the old plaster a bit with a spray bottle, and spraying the new plaster every so often so it doesn't dry out prematurely. This won't work if the base coat is too crumbly -- it's just make the base coat worse. But in that case, unless there are historical issues, I usually just replace the base coat(s) as well. Easier in the long run.

   Mike Hennessy
   Pittsburgh, PA