Are there differences to drywall joint compound and plaster?

Question

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?

Answer 1

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.

Answer 2

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