Plastering Guide: Cement Ratio, Thickness and Plastering vs Pointing
Summary
- Plastering is applied to create a strong base for your walls. It provides brickwork with a smooth, even surface for putty, painting, and tiling.
- Choose the right cement-sand ratio and plaster thickness. You should use 12 mm of thickness for internal walls and 15 mm to 20 mm for exterior walls.
- Use the right plastering process for strength and durability. Clean the surface, use the correct cement-sand ratio, apply the recommended thickness, and cure it properly.
- Order genuine high-quality construction essentials from HomeRun and get them delivered to your doorstep within 60 minutes.
Plastering is a process of applying a thin coating of mortar on walls and ceilings. It is applied to protect the brickwork from moisture and improve the durability of your house. The right plastering requires proper application with the correct cement-sand ratio and plastering thickness. In this guide, we'll explain what plastering is, plaster types, and the correct cement-sand ratio.
What Is Plastering?
Plastering is the process of applying a layer of mortar on walls and ceilings. It adds a protective layer that strengthens the wall. Plastering is also used to prepare the surface for painting or tiling.
Walls and ceilings are plastered to provide important protection. Here are the benefits of plastering:
Benefits of Plastering:
- Plaster is applied on the masonry to protect it from moisture and water damage.
- Plastering is applied on walls to increase strength and durability.
- Plastering creates a smooth base for applying putty and paint.
- Plasters cover cracks, joints, and uneven surfaces to provide a clean surface.
Plaster should not be confused with putty. Plaster is used to form the base layer over masonry. On the other hand, putty is a thin finishing coat applied before painting.
Types of Plaster
Let's look at the common types of plaster used in Indian homes:
- Cement plaster
- Gypsum plaster
- Lime plaster
- Mud plaster
- Waterproof plaster
| Type | Application | Main Benefit |
|---|---|---|
| Cement plaster | It is commonly used in interior and exterior walls. | Strong, durable, and weather-resistant |
| Gypsum plaster | Preferred for interior walls and ceilings. | Smooth finish and faster application |
| Lime plaster | Used in heritage buildings | Flexible and breathable |
| Mud plaster | Common in rural homes | Eco-friendly and economical |
| Waterproof plaster | Used in bathrooms, terraces, balconies. | Better moisture resistance |
Cement plaster is the most common choice for Indian homes. This is because cement plaster is highly durable and can be used in various weather conditions. Read our guide on Types of Cement in India to choose the right cement for your plastering project.
Cement Plaster Mix Ratio
The strength of the plaster depends on the cement-sand ratio. The correct ratio depends on the plaster's application.
| Cement-Sand Ratio | Recommended Use |
|---|---|
| 1:3 | For repairs and wet areas |
| 1:4 | For exterior walls |
| 1:5 and 1:6 | For internal walls |
Adding more cement to the mixture can improve the strength. But more cement can make the plaster prone to cracks. Read our complete guide on Water-Cement Ratio in Concrete and check how each material can influence the quality of your construction.
Use Quality Sand and Right Amount of Water The quality of the sand used can also affect the strength of the plaster. You should use clean and well-graded M-sand or river sand. The sand should be free from clay and other impurities. Read our guide on Types of Sand for Construction to understand the difference between river sand, M-sand, and P-sand. Add only enough water to make the mortar workable. Adding too much water can weaken the mixture. A weak mixture reduces strength and can cause the plaster to crack after it dries.
Plastering Thickness
The right thickness is as important as the cement-sand ratio. A thin plaster can expose uneven masonry and thick plaster can sag or develop cracks.
- Internal Walls: Thickness should be 12 mm. Apply only a single coat. This thickness is suitable for most residential walls. It will create a smooth base for putty and paint.
- Exterior Walls: Use a thickness of 15 mm to 20 mm. It can be applied in two coats. A 20 mm thickness will give better weather resistance and is less prone to cracks.
- Ceilings: A thickness of 6 mm to 8 mm is enough. A thinner coat is sufficient as ceilings are not exposed to extreme weather conditions.
If you are applying plaster on rough or uneven masonry, apply additional plaster. However, do not apply one thick layer of plaster to achieve the required thickness. You can apply in multiple coats to prevent sagging and cracking.
How to Plaster a Wall?
Follow these steps to apply plaster on your walls for long-lasting results:
- Clean the Surface: Remove dust, loose mortar, and old paint. Wet the wall slightly before you apply plaster.
- Prepare the Mortar: Mix the right amount of cement and sand. Add water gradually to the mixture to make a workable mixture. Make only the quantity that you can use before it starts to set.
- Apply the Base Coat: Spread the mortar evenly across. Use a straightedge to level the surface. Check that the wall remains plumb.
What is Plumb?: Plumb means that the wall or surface is perfectly vertical from top to bottom. Builders use a plumb bob or spirit level to check the alignment of the wall.
- Apply the Finishing Coat: Apply the final coat after the base coat has hardened. Use a wooden or steel float to smooth the surface.
- Cure the Plaster: Curing is an important step in plastering. Sprinkle water on the plaster for at least seven days. Curing will allow the cement to harden properly and gain strength.
Plastering vs Pointing: What's the Difference?
Plastering is the process of covering the entire wall or ceiling. A layer of mortar is added to create a smooth surface. Pointing is the process of filling and finishing the mortar joints between exposed bricks or stones. It is commonly used for decorative masonry as brick or stone surfaces remain visible.
Common Types of Pointing:
- Flush Pointing
- Weathered Pointing
- Recessed Pointing
- Keyed Pointing
Common Plastering Mistakes
Incorrect application or poor material can cause problems in plastered walls. Here are some mistakes to avoid:
- Using the incorrect cement-sand ratio.
- Applying plaster on a dry or dusty surface.
- Not curing the plaster properly.
- Applying an excessively thick coat.
- Using poor-quality sand.
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Frequently Asked Questions
What is the cement-sand ratio for wall plastering?
Use a 1:3 mix for wall repair and wet areas. A 1:4 mix is used for exterior walls for better durability. Use a 1:6 ratio for internal walls.
What is the correct thickness of plaster for internal and external walls?
The correct thickness for internal walls is 12 mm, and 6 mm to 8 mm for ceilings. For external walls, apply plaster of 15 mm to 20 mm thickness.
What is the difference between plastering and pointing?
Plastering is a wall finishing method in which cement mortar is spread over the entire surface. Pointing is a masonry finishing technique. It only fills the mortar joints and leaves the brick or stone exposed.
How do you replaster an old wall?
Remove the loose plaster from the wall. Repair cracks and hollow patches. Clean the surface properly. Wet the wall and apply fresh plaster.
How long should plaster cure before painting?
Cure the plaster with water for at least seven days before you apply putty or paint. Curing will improve the strength and will reduce the risk of cracking.
