Plastering mortar refers to the mortar plastered onto the surface of buildings or components. According to the construction site, it is divided into indoor plastering and outdoor plastering. The former includes the inner wall, ceiling, dado, floors and stairs, etc.; while the latter includes the outer wall, parapet wall, windowsill and balcony, etc. By functions, it is divided into ordinary plastering mortar and special-purpose plastering mortar (such as outer thermal insulation plastering mortar, cracking-resistant mortar, decorative mortar and waterproof mortar, etc.). According to the thickness used, it is divided into ordinary plastering mortar and thin-layer plastering mortar. For ordinary plastering mortar, the total plaster thickness is 20-35mm, and the plaster thickness of each layer is about 7mm; while for thin-layer plastering mortar, the total plaster thickness is 3-5mm, and the plaster thickness of each layer is 2-3mm. Ordinary plastering mortar is sometimes mixed on site, and sometimes produced in the factory, namely, ready-mixed mortar; while thin-layer plastering mortar is generally produced in the factory.
On-site mixed plastering mortar can be classified by its compositions into cement-lime composite mortar and cement mortar. Its varieties are named after the proportions of components. For example, 1:3 cement mortar indicates that the mortar compositions are 1 part of cement and 3 parts of sand by volume; 114 composite mortar shows that the ratio of cement, lime putty and sand in mortar is 1:1:4. The commonly used plastering mortar includes 114 composite mortar, 116 composite mortar, 1:3 cement mortar and 1:2cement mortar, etc. Ready-mixed mortar by industrial production is generally represented by its strength grade, which is divided into M5, M10, M15 and M20. Thin-layer mortar is mainly used for overlay protective mortar of exterior insulation and finish systems (EIFS), and commonly known as cracking-resistant mortar, rendering coat mortar, and thin-layer plaster. Each variety has only one strength grade, so is directly named in general.