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The drywall store near me told me the they don't have (or use) joint compound for drywall seams, they use something called "slow plaster" (free translation) for over the drywall tape with the same or better results.

Any truth to that? Why would I choose one over the other?

4

There are huge differences. I am sure a professional tradesman can go over the exact specifics but here is my common man take (even though I have drywalled too many houses to remember):

  • plaster generally sets more quickly
  • plaster is thicker
  • plaster can be applied more thickly (joint compound you get about 1/8")
  • plaster to me is like working with thinset except you will see the plaster as thinset is almost always hidden
  • joint compound can be sanded more easily
  • joint compound is more prone to cracking (this is about application too)
  • I would personally only use plaster for a very small area that is having cracking problems. I have done some plaster work and literally drove me nuts. Also I do not consider myself artistic. When applying plaster it is an art. If you over apply sanding it down is way harder than joint compound. I would never think about plastering all of a drywall in a house.

The only thing else I can add is I don't know what they consider slow plaster. I am sure that refers to the setting time. The plaster I have used starts setting in 30-60 minutes (hence my reference to thinset). Maybe they have something that lasts longer or maybe it is some combo plaster/compound.

  • Searching the net I've found just a few mentions to plaster and drywall. One of them is talking about "plaster skimming", which is done on the whole wall (from what I understand). The other mention that I've found says that joint compound is more britle, cracks easily and needs 3 coats to be applied, plaster is harder (and hard to sand) and can be applied at once. – Luiz Borges Dec 9 '14 at 18:16
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    If you are a master plasterer -which is a true art - then I could believe that plaster might take less time and it is surely more durable. I for one am not a master plasterer and if I did a house like this it would look like a kid did the mudding. 99% of the time if you use joint compound correctly you won't have issues. – DMoore Dec 9 '14 at 20:08
  • Thanks, I will go for the right stuff then. The powdered variety is easier to come by here, it dries in 90 minutes. The ready-mix in buckets takes a whole day to dry and isn't so easy to find. – Luiz Borges Dec 9 '14 at 20:19
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Plaster of Paris sets faster and cracks less. The downside is it is much harder to sand once it is set.

There is an alternative... you can add crack resistance and quicken drying time by mixing the two. The easiest way is to buy pre-mixed drywall compound and sprinkling plaster paris powder into it and then mixing together. add more or less depending on the type of results you are looking for

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