Plastering: Plastering is the process for using mortar coats on the exterior of walls, columns, ceiling to provide a sleek finish. Mortar that is utilized in plastering may range from lime mortar, cement mortar or lime-cement mortar. Lime mortar that is utilized should contain fat lime to sand ratio of 1 : 3 or 1 : 4. If hydraulic lime is applied, it’s mix ratio (lime: sand) is 1 : 2. Cement mortar of 1 : 4 or 1 : 6 mix is mostly utilized for plastering, richer mix is applied for outside walls. Lime-cement mortar is the combination of lime mortar and cement mortar in the ratio of (cement : lime : sand) 1 : 1 : 6 or 1 : 1 : 8 or 1 : 2 : 8. Lime-cement mortar can save significant plastering cost.
Lime mortar is generally applied in 3 coats whereas cement mortar is used in two or three coats toward the stone and brick masonry. Cement mortar is used in two or three coats toward concrete surfaces.
Most often, one coat of cement mortar is used for concrete building blocks.
The first coat is useful for attaining level surface. The final coat produces smooth surface. When three coats are applied, second coat is called floating coat. The average density of first coat is 10 to 15 mm. The density of middle coat is 6–8 mm. The density of final coat is just 2 to 3 mm. When single coat is applied, the density remains among 6 to 12 mm. Such coats are useful for concrete surfaces not uncovered to rain.
Pointing: In some cases, special mortar finishing work is applied to the uncovered joints in place of providing plaster to the whole surface of the masonry. It is known as pointing. It comprises of slanting the joints to a depth of 10 mm to 20 mm and stuffing it with richer mortar mixes. Toward lime mortar, the ratio of pointing mix is 1 : 2 and for cement mortar pointing mix is applied in the ratio of 1 : 3. Pointing is mostly suitable for stone masonry as stones contain eye-catching colors and strong resistance power against water penetration. Pointing makes weaker part of masonry (i.e. to joints) more accurate and it enhances the aesthetic view of the masonry.
Given below, some points of variations among plastering and pointing.