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Although they are used for similar tasks, spackle and joint compound are not the same. Joint compound, also known as drywall mud, consists of limestone and gypsum and is primarily used for large-scale projects like taping and finishing seams on new drywall. Spackle is composed of gypsum and binding agents, making it a thicker compound best suited for small wall repairs like filling nail holes or cracks, as it dries quickly and is easy to sand. For small repairs, either product can be suitable. However, you can use joint compound for small jobs in place of spackle, but you cannot use spackle for large-scale taping and mudding projects.

Plaster itself has a higher R-value than drywall. However, there are other considerations surrounding plaster and insulation. As a general rule, it's easier to obtain consistency in insulating value and quality when working with drywall rather than plaster. Plaster walls often don't contain any insulation behind the wall covering by design, and careful evaluation is necessary when choosing to add it.

Yes, you can apply new plaster over an existing plaster surface, such as a wall or ceiling, provided the old plaster is in good condition. Before you begin, check the stability of the existing plaster. The surface must be clean, free of loose material, and have no peeling paint. It is also recommended to roughen the surface slightly to promote adhesion. For older plaster, applying a base coat like a PVA emulsion or a specific bonding agent or primer is crucial. This step makes the existing plaster less porous and ensures the new and old layers adhere properly for a smooth, long-lasting finish.

You can plaster over regular drywall, but it's essential to prepare the surface properly. Before plastering, the drywall should be clean, free of dust, and any loose or peeling paint should be removed. Applying a primer specifically designed for plastering can improve adhesion. Some professionals recommend applying a base coat of plaster or joint compound to create a better surface for the plaster to adhere to. Proper preparation ensures a smooth and durable plaster finish over regular drywall.