This depends on how much plaster is applied and in how many layers, but a decent estimate is around 150 square feet. If you are applying only two coats on a small wall, there is a chance you may only need one or two gallons for the entire project. If you are plastering a large living room wall with high ceilings, using one of the more involved techniques–like Scagliola–that requires several coats, expect the project materials costs to add up quickly. 

Both plaster and drywall are durable wall finishes, but they differ significantly in installation, cost, performance, and aesthetics.

Installation & Cost: Drywall installation is faster and more affordable, typically costing $1.50 to $3 per square foot. It uses premade sheets, making it a more accessible DIY project. Plastering is a labor-intensive craft that requires specialized skills, pushing costs to $2 to $10 per square foot. It involves applying a wet paste over a lath framework.

Durability & Performance: Plaster is generally more durable, longer-lasting, and provides superior soundproofing. It is also a better insulator, which can help reduce energy costs. Drywall is easier to remove for future renovations.

Aesthetics: Drywall provides a smooth, uniform surface ready for paint or texture. Plaster offers a high-end, naturally textured look that can hide imperfections and is often preferred for achieving a classic or historic aesthetic.

Which is better? The choice depends on your priorities. Drywall is ideal for those prioritizing a lower upfront cost, faster installation, and DIY potential. Plaster is the better option for a higher-end project where durability, soundproofing, and a unique, premium finish are more important than the initial cost.

Vinegar and bleach are effective options for removing mold from drywall. Vinegar is a better choice if you have a smaller mold issue while bleach is best if you have a larger mold problem. If the area you're cleaning has limited ventilation, using vinegar would be a better option. In that case, you could mix vinegar with baking soda to remove more stubborn mold growth.

The short answer is yes, a sagging plaster ceiling is dangerous. Sagging plaster on a wall is something you should fix immediately, but it isn’t a major concern. If the same type of sagging occurs on a ceiling, however, you could be in danger of your ceiling falling in large chunks. When plaster sags, it loses its strength and ability to hold itself up. The bonds that hold it together are strong, though, so if a sagging area falls, it will take large pieces down with it.