Plaster is used in construction to provide a durable and weather resistant finish to exterior walls. For interiors, plastering helps to prepare a surface for aesthetic decoration such as the application of paint or wallpaper. Plaster can be made from a variety of materials. Some of the most popular plaster materials used for basecoat and finishing are made from natural materials either mined or as a by-product. 

The different characteristics of plaster can determine its suitability in home construction. There are three basic components that make up a plaster compound: the main structural ingredient, a binding agent, and some type of fibre. 

Plaster Composition

In most plaster compositions, sand is used as the structural component with the exception of gypsum plaster. For example, Parex supplies such as Parex render requires the use of a structural component like sand to combine with the binding agent present in the render. Water helps to combine both components and as the water evaporates, the plaster cures and creates a hard finish. 

Fibre is added to the plaster mix in order to increase strength and serve as reinforcement. Some examples of fibre added to plaster are wool, straw, and cattail. 

Gypsum plaster

This type of plaster is composed of a mined mineral, calcium sulphate. It is commonly used in interior walls because gypsum plaster can be used to create texture and patterns. There are manufacturers of rendering materials specialising in the use of gypsum. Some examples of gypsum-based render are Parex Paraguard, Monorex GM, and Monorex GFParex

Since gypsum plaster is water soluble, it is not ideal for use on exterior walls, but it creates a hard and durable finish which is perfect for interior walls and ceilings. 

Lime plaster

Of all the plaster materials available today, lime plaster is considered to be the strongest. It creates excellent protection when applied over cement, brick, and block walls which makes it ideal for exterior walls. One of the disadvantages, however, is that it takes a long time to set. A plasterer also needs to be experienced with handling lime because of its consistency. 

Cement plaster

This plaster composition is usually made with a mixture of cement, sand, and fibre. In some instances, a small amount of lime may be added to the mixture to make it more elastic and prevent cracks. Cement plaster is widely used for exterior walls. It is both durable and easy to apply. One of the disadvantages of cement plaster is its tendency to crack. However, the proper application can ensure that this render will last a lifetime. 

Earthen plasters

Perhaps the oldest type of plaster, earthen plasters have become quite popular again as more builders encourage the use of natural materials such as adobe, and compacted earth.

This type of plaster has to be made from scratch since not many manufacturers offer it in ready to mix bags. It will also require some experimentation to get the right consistency. While earthen plaster is generally environment-friendly, it may not always adhere with local building codes in many areas.