Plastering is an ancient building technique to cover the exposed surface and give protective surface against penetration of rain water, other atmospheric agencies like vermin and improves the appearance of the structure and gives decorative effects.
Nowadays there are number of trends, technology advancements and innovations with many applications in the construction sector. They all aim at making construction faster and delivering higher and better performance. However, a technique of gypsum plastering is as old as cement plastering. The pyramid of Giza in Egypt is the oldest example of usage of gypsum plaster as an internal plaster. It is proof of durability and performance of gypsum plaster.
Gypsum building plasters are used extensively in many countries of the world including Australia, Canada, United Kingdom, United States of America and USSR, for general building operations and for the manufacture of performed gypsum building products which have the specific advantages of lightness and high fire resistance.
Cement Plaster vs Gypsum Plaster
Here we give you brief comparison of Cement Plaster vs Gypsum Plaster:
01. Composition
- The sand cement plaster is a homogeneous mixture of Portland cement and sand with water. The sand and cement are mixed at the site in different ratios. Nowadays it is also available in Ready-made packages.
- In gypsum plaster, gypsum is used as a binding material instead of Portland cement. It is ready to use and does not need sand.
02. Area Recommendation
- It is used on both surfaces internal as well as external.
- It is used only in internal walls and ceilings. Again it cannot be used in wet areas like a toilet, bath, kitchen, wash area, etc.
03. Thickness
- The thickness of cement plaster should not be less than 10 mm. The Thickness of cement plaster may vary and it depends on the surfaces to be covered and its plumb and texture.
- For example, for brick walls thickness of plaster is 12 mm to 20 mm.
- For underside of the RCC ceiling/ roof, thickness of plaster is generally 10 to 12 mm.
- The thickness of undercoat of gypsum plasters are generally 11 mm thick for walls and 8 mm thick for ceiling and finish coat plaster is 2 mm thick.
04. Insulation Properties
- It has more or less same thermal conductivity as gypsum.
- Gypsum plaster has low thermal conductivity and good thermal properties and ensures energy and power saving.
05. Flexural- Tensile Strength
- Cement mortar is basically weak in tension and flexural strength and hence prone to cracking. Further most of cracking happens due to shrinkage, which is quite common.
- Gypsum plasters exhibit high tensile and flexural strength. They are less prone to cracking.
06. Non-Toxic and Anti-fungus
- Cement plaster is not 100 % permeable to water vapour. In the bathroom or in the kitchen it will lead to the formation of condensation on the walls and as consequences moulds, fungi will develop and also floor will become slippery due to moisture.
- Gypsum plaster is not affected by insects and does not nourish mould growth of fungal. They pose no health hazards and are therefore frequently specified in hospitals and clinics.
07. Curing
- Pre-Curing and Post-Curing are necessary for cement sand plaster.
- Cement plaster needs an enormous amount of water during its curing period. The site becomes dirty due to it and also needs more time for works.
- Gypsum plaster requires no water curing and should be permitted to dry out as quickly as possible.
- Gypsum plaster requires no curing which saves up on all that water.
08. Fire Inhibitor
- Cement plaster up to 200 to 300 C acts as refractory material and resists fire but later it becomes brittle and cracks and falls and looses bond with wall.
- Gypsum is non-combustible and contains a high content of crystal water. In the event of a fire, it acts as a barrier and will protect the blockwork, concrete and steel.
09. Acoustic Properties
- It has more or less same acoustics properties.
- Gypsum as a binder is used in the manufacture of acoustic tiles and plasters, a contributory factor to the absorption of air borne sounds.
10. Bonding Properties
- It cannot be applied on the smooth surface.
- Due to the nature and structure of gypsum, it exhibits excellent bonding properties hence is applied in a single coat on RCC ceilings, internal bare-brick walls, AAC blocks and concrete columns.
- It can be applied on smooth as well rough surfaces.
11. Rust Inhibitor
- Cement plaster is not a rust inhibitor.
- Gypsum Plaster is the perfect rust preventive agent and also inhibits corrosion of electric metal fittings, pipes etc. Metal lathing embedded in gypsum plaster will not corrode or rust and serves durable and long life.
12. Ease of Application
- The mixture of the sand and cement is to be done on site in different ratios. This is generally done and controlled by mostly unskilled labour and hence not likely to be accurate and perfect.
- Gypsum plaster is pre-mixed and available in easy to handle bags. Only addition of water is required. A single coat application is resulting in less wastage of time, labour and material.
13. Aesthetic Finish
- After sand cement plaster, POP punning is required for the better and leveled surface finish.
- The space looks smaller and unattractive as it is dark grey in colour.
- Gypsum plaster provides a smooth interior finish for ceiling, walls and is ideal back ground for good quality paints and wallpaper finishes.
- The room space looks large and beautiful as gypsum plaster is pure white in colour.
14. Absence of Shrinkage Cracking
- Development of shrinkage cracks is quite frequent in cement plaster.
- Gypsum plaster do not shrink like cement during the drying out and hardening process.
15. Light Weight
- Density of cement plaster is higher than gypsum plaster; hence the load on the building is increased as compared to gypsum plaster and needs water to attain strength.
- Gypsum plaster is light in weight and total strength is achieved in air.
16. Workability
- Cement plaster is comparative gives a rough finish.
- Gypsum plaster is easily workable for excellent finish. It gives smooth finish compatible to receive all type of paints. Various surface textures and surface hardness can be obtained.
17. Setting Time
- Minimum Twenty-four-hour interval between coats of interior Portland cement plaster. After a 48-hours period finished coat plaster may be applied to interior cement base coats.
- Setting time of gypsum plaster can be controlled. Time between two successive coats is very small.
18. Wastage
- Percentage of wastage is higher during application.
- Percentage of wastage is nominal during application.
19. Cost
- The application of cement plaster is time-consuming process hence increases the project cost.
- However, per square feet cost of cement plaster is less than gypsum plaster due to higher cost of gypsum.
- The application of gypsum plaster is time saving process, thus decreases the project cost.
- Gypsum plaster is costlier than cement plaster for same thickness.
Conclusion
From the above comparison of Cement Plaster vs Gypsum Plaster, Gypsum plaster is advisable as compared to cement plaster asit gives better-desired finish and performance. Gypsum plaster is also advisable where river sand/natural sand is not easily available for the construction. Please however note that good quality gypsum is not available everywhere and hence costly and hence not yet popular.