Do you want to remodel your current house or start constructing a new one? One of the most essential yet often debated aspects of construction is the plastering material.
A common question among homeowners and builders is, “Which is better, cement plaster or gypsum plaster?”
Both cement plaster and gypsum plaster are widely used in Australia and around the world for different purposes, and each has its own set of advantages and disadvantages.
This article will help you explore the differences between these two options, outlining their features, benefits, and best use cases.
With this information, you’ll be better equipped to choose the right plaster for your project.
Let’s get straight to the point
Cement plaster and gypsum plaster are both widely used in construction, each with its own advantages and disadvantages.
Cement plaster, made from cement, sand, and water, is durable, moisture-resistant, and ideal for exterior walls, but it’s labour-intensive and prone to cracking.
Gypsum plaster, made from gypsum powder and water, sets quickly, is lightweight, and provides a smooth finish for interiors, but isn’t suitable for wet areas or exterior use.
Cement is cheaper but takes longer to apply, while gypsum costs more but reduces labour time. The best choice depends on the project’s location, time constraints, and maintenance needs.
What Is Cement Plaster?
Cement plaster, also known as cement mortar plaster, is a mixture of cement, sand, and water.
It is a versatile material used to coat and protect both interior and exterior walls. When applied to a surface, it hardens over time to create a durable, solid finish.
How Cement Plaster Is Made
The typical composition of cement plaster involves mixing cement and sand in ratios ranging from 1:3 to 1:6.
Water is gradually added to achieve the required consistency, and the plaster is then applied to clean walls using either a trowel or spray equipment.
Benefits of Cement Plaster
- Durability: Cement plaster is highly durable, making it a perfect choice for exterior surfaces where strength is essential.
- Moisture resistance: It offers better moisture resistance compared to other materials, helping to protect walls from damp conditions.
- Fire resistance: Cement plaster provides a fire-resistant layer, adding an extra level of safety to your home.
- Versatile application: This material can be applied to various surfaces, including brick, concrete, and stone.
Drawbacks of Cement Plaster
Despite its strength, cement plaster does have some disadvantages:
- Labour-intensive application: Applying cement plaster can be a time-consuming process, especially when multiple layers are needed.
- Curing requirement: Cement plaster needs to be kept moist during the curing process, typically over several days, to avoid cracks.
- Tendency to crack: Cement plaster is prone to shrinkage cracking, particularly during drying, which may require patching.
What Is Gypsum Plaster?
Gypsum plaster, commonly referred to as plaster of Paris, is made from a mixture of gypsum powder, water, and additives.
It is primarily used for interior walls and ceilings and is appreciated for its smooth finish and ease of application.
How Gypsum Plaster Is Made
The gypsum used to create this plaster is either naturally mined or produced as a byproduct of certain industrial processes.
The material is then calcined, which involves heating it to remove water, producing a fine powder.
When this powder is mixed with water, it creates a paste that can be easily applied to walls and ceilings.
Benefits of Gypsum Plaster
- Quick setting time: Unlike cement plaster, gypsum plaster sets quickly, often within a few hours.
- Smooth finish: Gypsum provides a naturally smooth surface without the need for extensive polishing.
- Lightweight: Gypsum plaster is much lighter than cement plaster, reducing the load on the building structure.
- Fire-resistant: Gypsum has excellent fireproofing qualities, making it a safer choice for interior spaces.
- Mould-resistant: Gypsum plaster has anti-fungal properties, preventing the growth of mould and mildew in humid conditions.
- Eco-friendly: Being a natural material, gypsum plaster is environmentally friendly and contributes to a healthy indoor climate by regulating moisture levels.
Drawbacks of Gypsum Plaster
While gypsum plaster has its advantages, it is not suitable for all applications:
- Limited to interiors: Unlike cement plaster, gypsum plaster cannot be used for exterior surfaces. It is vulnerable to moisture and is not recommended for use in wet areas like bathrooms or kitchens.
- Higher cost: Although the initial cost of gypsum plaster may be higher, it can save on labour costs due to its quick application time.
Cement Plaster vs Gypsum Plaster: A Detailed Comparison
1. Raw Materials
- Cement plaster: Made from a mix of Portland cement, sand, and water. The ingredients are readily available and can be mixed on-site.
- Gypsum plaster: Made from gypsum powder, which is combined with water and some additives.
2. Setting Time
- Cement plaster: Requires at least 24 hours of drying between coats, and the complete curing process can take up to 48 hours or more.
- Gypsum plaster: Sets within a few hours, allowing for faster project completion.
3. Application Area
- Cement plaster: Suitable for both interior and exterior surfaces. It can be used in a variety of environments, including wet areas like bathrooms.
- Gypsum plaster: Best suited for interior walls and ceilings. It should not be used in damp or wet environments.
4. Thickness
- Cement plaster: Requires a minimum thickness of 10mm for effective coverage.
- Gypsum plaster: Requires a thinner application—usually around 8mm to 11mm—which makes it easier to apply and reduces material use.
5. Non-toxic and Anti-Fungal Properties
- Cement plaster Can develop mould and mildew in high-moisture areas, especially if not properly sealed.
- Gypsum plaster: Naturally resists mould and fungi, making it a hygienic choice for indoor spaces, particularly in hospitals or clinics.
6. Cracking
- Cement plaster: Prone to shrinkage cracks during the drying process, requiring careful curing to avoid this issue.
- Gypsum plaster Does not shrink, which means no cracking during the drying phase.
7. Cost Comparison
- Cement plaster: While cement plaster is generally cheaper per square foot, its longer application time and labour-intensive process can increase the overall cost of a project.
- Gypsum plaster: Though initially more expensive, it can reduce labour costs and speed up the construction timeline.
Expert Tips for Choosing Between Cement and Gypsum Plaster
If you’re still undecided on which plaster to choose, here are some expert tips to help you:
1. Consider the Application Area
If you are plastering exterior walls or areas prone to moisture, such as bathrooms or laundries, then cement plaster is the better option. For interior walls and ceilings where a smooth finish is essential, gypsum plaster is ideal.
2. Weigh Time vs. Cost
If you’re on a tight schedule, the fast setting time of gypsum plaster could be more convenient, even if it’s slightly more expensive. Cement plaster, on the other hand, is more affordable but requires longer curing times.
3. Focus on Maintenance
Gypsum plaster requires less maintenance because it is less likely to crack or develop mould. Cement plaster might need more frequent inspections and repairs to maintain its appearance over time.
4. Evaluate Environmental Impact
If sustainability is important to you, gypsum plaster is the more eco-friendly option due to its natural origin and recyclability.
Conclusion
Both cement plaster and gypsum plaster have their place in the Australian building industry.
Cement plaster is more versatile and durable, particularly for exterior applications and wet environments, while gypsum plaster offers a smooth finish, quick setting, and lighter weight, making it ideal for interior walls.
Ultimately, the best plaster depends on the specific needs of your project. Whether you’re looking for durability with cement plaster or a fast, smooth finish with gypsum plaster, understanding their properties will help you make an informed decision.
Frequently Asked Questions
Can I Use Cement Plaster For Interior Walls?
Yes, cement plaster can be used for interior walls. It provides a strong and durable finish, making it suitable for areas where strength and resistance to wear are important.
Cement plaster is commonly used in basements, foundations, and other interior surfaces that require a robust wall finish.
However, it’s worth considering that cement plaster may not provide the same level of smoothness as gypsum plaster.
If you desire a perfectly smooth and leveled surface for your interior walls, gypsum plaster might be a better option.
Gypsum plaster is known for its ability to create a seamless and flawless finish, which is often desired in interior spaces.
Is Gypsum Plaster Suitable For Exterior Applications?
Gypsum plaster is generally not recommended for exterior applications due to its lower resistance to moisture and limited durability compared to cement plaster.
Exterior surfaces are exposed to harsh weather conditions, and cement plaster provides better protection against moisture infiltration and damage.
Cement plaster is the preferred choice for exterior applications as it offers superior strength, durability, and resistance to the elements.
It can withstand temperature changes, moisture, and other external factors, making it suitable for long-lasting finishes on exterior walls.
Can Gypsum Plaster Be Used In Areas With High Humidity?
Gypsum plaster is not recommended for areas with high humidity levels, such as bathrooms, kitchens, or areas prone to water splashes.
Although gypsum plaster has some moisture-resistant properties, it is not as suitable as cement plaster for areas with excessive moisture.
High humidity can cause gypsum plaster to deteriorate over time, leading to potential mold growth or other moisture-related issues.
In such areas, it is advisable to use cement plaster or consider alternative moisture-resistant materials specifically designed for humid environments.
Does Gypsum Plaster Require Any Special Preparation Before Application?
Yes, there are a few essential preparations to consider before applying gypsum plaster:
- Surface cleaning: Ensure that the surface is clean, free from dust, grease, and loose particles. Cleaning the surface thoroughly helps in achieving better adhesion and a smooth finish.
- Priming: It is recommended to apply a primer or a coat of diluted gypsum plaster on the surface before the actual application. Priming helps in improving the bond between the surface and the plaster, enhancing the overall finish.
- Mixing consistency: Follow the manufacturer’s instructions for mixing gypsum plaster with water to achieve the right consistency. Proper consistency ensures easier application and a uniform finish.
- Application technique: Gypsum plaster is typically applied in multiple thin layers. Each layer should be allowed to dry partially before applying the next layer. This helps in preventing cracks and achieving a smooth and even finish.
Is Gypsum Plaster Fire-Resistant?
Yes, gypsum plaster is inherently fire-resistant. Gypsum, the main component of gypsum plaster, contains water molecules within its crystalline structure.
When exposed to fire, the water molecules are released as steam, acting as a barrier to slow down the spread of flames.
Due to its fire-resistant properties, gypsum plaster is commonly used in fire-rated assemblies and structures.
It helps to improve the fire safety of buildings by providing additional time for occupants to evacuate and reducing the spread of fire within a space.
However, it’s important to note that gypsum plaster is not completely fireproof. In the event of a severe fire, prolonged exposure to high temperatures can eventually cause the plaster to degrade.
Therefore, it is crucial to adhere to building codes, regulations, and fire safety measures when incorporating gypsum plaster into a construction project.
