Recommended Plaster Specifications
A list of specifications for mixes suitable for various situations, which cover single-coat, two-coat and three-coat work is given in the table below.
|
No. of Coat of Plaster |
Situation |
Mix proportion by volume (Cement:Lime:Sand) |
| Single coat plaster | Both internal and external | 1:0:3 |
| 1:0:4 | ||
| 1:0:6 | ||
| 1:1:6 | ||
| 1:2:9 | ||
| Two coat plaster | Both internal and external | |
| (a) under coat | 1:0:3 | |
| 1:0:4 | ||
| 1:0:6 | ||
| 1:1:6 | ||
| (b) Finishing Coat | 1:0:3 to 6 | |
| 1:1:6 | ||
| 1:2:9 | ||
| Three coat plaster | Very rough surface; both internal and external | |
| (a) Base coat | 1:0:3 | |
| 1:0:4 | ||
| 1:0:6 | ||
| 1:1:6 | ||
| (b) Second coat | 1:0:3 to 6 | |
| 1:1:6 | ||
| 1:2:9 | ||
| (c) Finishing coat | Fat lime and fine sand or marble dust in equal proportions |
Notes to Remember
- Where two or three coat plasters are adopted, as far as possible the mix for the under coats should contain coarse sand (conforming to grading zone 2) having fineness modulus not less than 2.0
- For single coat plaster the fineness modulus of sand should be as far as possible 1.5. The strength of plaster mix gets reduced with the reduction in the fineness modulus of sand.