How Plastering Can Improve Soundproofing in Your Home

Creating a quiet and peaceful home environment is more important than ever, especially with the increasing noise from urban living and busy households. While many traditional soundproofing methods involve high-tech solutions or bulky materials, plastering offers a surprisingly effective and often overlooked way to reduce noise. 

Whether you’re dealing with traffic sounds, noisy neighbours, or simply the everyday hum of a busy household, plastering, whether in its traditional form, acoustic plaster, or acoustic plasterboard, can significantly enhance your home’s soundproofing. In this guide, we’ll explore how plastering techniques can help you create a more peaceful home by blocking and absorbing unwanted noise, with tips and real-world examples based on my own experience in the field.

Plastering Enhances Soundproofing in Your Home

Now that we’ve covered the basics of soundproofing, let’s dive into how plastering can play a pivotal role in improving your home’s acoustics. Plaster, in its various forms, has been used for centuries to enhance the aesthetics and functionality of homes, but its ability to improve soundproofing often goes unnoticed.

Traditional Plaster vs Acoustic Plaster

Let’s start by distinguishing between traditional plaster and the more modern acoustic plaster. Both types of plaster offer soundproofing benefits, but their effectiveness varies depending on the specific needs of your home.

However, acoustic plaster goes a step further. This isn’t your run-of-the-mill plaster; it’s specially formulated with additives like mineral wool or granulated cork, which improve its ability to trap sound waves and absorb sound energy. I’ve had clients in apartments in the CBD who have used acoustic plaster to not only reduce the amount of noise coming through the walls but also control reverberation inside rooms, especially in spaces like home theatres and offices. The result? A smoother, quieter environment that doesn’t make you feel like you’re living in a tin can.

Plaster’s Role in Sound Insulation

Plaster plays a dual role in soundproofing — it both blocks sound and absorbs it. When it comes to sound blocking (or insulation), plaster creates a dense barrier that can stop noise from passing through walls. This is especially beneficial if you’re dealing with airborne sound like music, voices, or traffic noise.

On the other hand, acoustic plaster does a fantastic job at absorbing sound within a room, reducing echoes and reverberation. It acts like a sponge for sound, absorbing excess noise and preventing it from bouncing around. A real example from a recent project in Fitzroy comes to mind. We plastered an open-plan living space, and the difference in sound quality was immediate. The space felt more intimate, and conversations didn’t echo, making it easier to hear each other without raising voices. This is a major plus for homes with large, open areas that tend to amplify sound.

Acoustic Plasterboard: A Popular Choice for Soundproofing

If you’re looking for a more cost-effective solution, acoustic plasterboard (or soundproof plasterboard) is another option that’s commonly used in both residential and commercial spaces. Unlike regular plasterboard, this type of plasterboard is made with a denser gypsum core and often contains additives like fibreglass or viscoelastic polymers. These materials enhance their ability to block sound, making them a go-to solution for reducing noise transmission between rooms.

Why Plastering is Effective for Soundproofing

What makes plaster an effective soundproofing material is its ability to add mass to a wall or ceiling. The heavier the material, the harder it is for sound to pass through. Traditional plaster and acoustic plaster work by increasing the mass of the surface, which makes it significantly harder for sound waves to penetrate.

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Top Plastering Techniques for Soundproofing Your Home

Plastering is one of the most reliable methods for enhancing soundproofing in your home. However, achieving the best results requires a solid understanding of plastering techniques and the application process. In this section, I’ll walk you through some of the best plastering techniques to maximise your home’s acoustic performance.

Layering and Thickness: Best Practices for Plaster Application

When it comes to soundproofing with plaster, thickness matters. You might think that a thicker coat of plaster would do the trick, but applying multiple thin layers of plaster often works better. Here’s why:

Think of it like a cake. A single thick layer might look good, but it’s often the layers of frosting, sponge, and filling that give it structure and depth. Similarly, when you apply multiple thin layers of plaster, each layer acts like an individual barrier that helps to trap sound waves and prevent them from passing through.

During a renovation I did in a flat in Hawthorn, the client was concerned about noisy neighbours. We applied three thin layers of plaster, each with a light sanding between applications, to ensure maximum adhesion and a smooth finish. The result was a significant reduction in noise, particularly in the bedroom, which faced the main road. The sound didn’t completely vanish, but it went from intrusive to just a dull hum.

The general rule of thumb when using plaster for soundproofing is to aim for a layer thickness of at least 12mm. This thickness, when applied in layers, creates enough mass to block noise effectively. However, it’s also important not to go overboard with thickness, as it can cause the plaster to crack or weaken over time.

Combining Plaster with Other Soundproofing Materials

Plastering on its own is excellent for blocking airborne sound, but for optimal performance, it works best when combined with other soundproofing materials. Here’s how you can enhance your plastering efforts:

1. Acoustic Insulation: Filling the wall cavity with acoustic insulation, like mineral wool or fibreglass, can improve soundproofing dramatically. These materials work by absorbing sound energy within the wall cavity, preventing it from vibrating through the wall.
   A great example of this was a project I worked on in South Yarra, where we added Rockwool insulation between the studs before applying the plaster. This combination was a game-changer for the family living there, who were previously hearing every footstep and conversation from the apartment next door. With the added insulation, they found the noise from the adjoining apartment was reduced by over 50%.
   
2. Mass Loaded Vinyl (MLV): If you’re looking to block out low-frequency noise (like bass or heavy thumping), Mass Loaded Vinyl (MLV) is a fantastic option. This dense, flexible material works as a barrier to airborne sound, and when layered between plaster and drywall, it provides an excellent soundproofing system.
   During a commercial project in a busy part of the city, we used MLV in conjunction with acoustic plasterboard to reduce both airborne and impact sound. The combination of plaster, insulation, and MLV created a multi-layered barrier that blocked out a significant amount of street noise and office chatter.
   
3. Resilient Channels: For even better results, consider using resilient channels or sound isolation clips. These are metal channels that decouple the plasterboard from the studs, reducing the amount of sound that travels through the structure. While these systems can be more expensive and require additional installation steps, they are highly effective in reducing impact noise like footsteps.
   I worked on a townhouse renovation in Fitzroy, where we used resilient channels on the ceiling to help isolate sound from the upstairs tenants. The results were impressive, reducing not only noise from footsteps but also the sounds of furniture being moved.
   

Surface Preparation for Optimal Adhesion

For plastering to be effective, the surface you’re applying it to must be prepared correctly. If the surface isn’t clean or smooth, your plaster will not adhere properly, and the soundproofing results will be compromised.

Here’s a checklist for proper surface preparation:

• Clean the Wall Surface: Make sure the wall is free from dust, grease, or any other contaminants that could prevent the plaster from sticking. In Melbourne, where we can get a bit of humidity, it’s important to check for any mould or moisture issues before plastering.
  
• Seal Cracks and Holes: Before applying plaster, use an acoustic sealant or caulk to fill in any cracks, gaps, or holes. Even small imperfections can undermine your soundproofing efforts. For example, during a job in Port Melbourne, I found that the walls had small gaps that weren’t visible at first glance. Sealing those gaps before plastering made a huge difference in the final results.
  
• Priming: If the wall has been painted, lightly sand it to improve plaster adhesion. You may need to apply a primer to ensure that the plaster bonds properly to the surface. If you’re working with newer drywall, you’ll want to ensure it’s properly primed before applying the plaster to avoid cracking.
  

Plaster Application Methods: Manual vs Machine

You can apply plaster either manually or with a machine. The manual method is often preferred by traditional plasterers because it allows for greater control, especially in custom work. It’s perfect for smaller, intricate projects or when you want a seamless finish.

On larger projects, however, like the renovation of multi-level apartments I worked on in Melbourne, we used plastering machines. These machines can apply a uniform coat quickly and efficiently. The downside? They require a skilled operator to ensure the plaster goes on evenly and smoothly, avoiding excess thickness or clumping that can lead to cracking.

The choice between manual and machine plastering often comes down to the size of the project and the desired finish.

Comparing Plaster to Other Soundproofing Methods

Now that we’ve covered plastering techniques and how they contribute to soundproofing, let’s compare plaster to other popular soundproofing methods. While plaster is an excellent material for blocking and absorbing sound, it’s important to consider whether it’s the best solution for your specific needs, or if combining it with other materials could deliver even better results.

Traditional Soundproofing Materials vs Plaster

When you think of soundproofing, your mind might jump to materials like foam panels, fibreglass, or soundproof windows. These materials are great at absorbing sound, but they often fall short when it comes to blocking sound from passing through walls and ceilings. This is where plaster comes in. Plaster is dense, heavy, and mass-loaded, making it one of the best materials for sound insulation. It’s particularly effective when dealing with airborne noise like traffic or loud music.

Here’s a quick comparison:

As you can see, plaster generally offers better sound blocking, while foam panels and fibreglass excel at absorbing sound. In many cases, a combination of both types of materials is the best route for comprehensive soundproofing.

Plaster’s Durability and Cost-Effectiveness

One of the major benefits of plaster, especially in residential projects, is its durability. Once applied, plaster requires very little maintenance and will last for decades. It’s fire-resistant and long-lasting, making it an ideal choice for homes, schools, and offices.

In comparison, materials like foam panels and fibreglass are more prone to damage and need replacing or maintenance more frequently. I’ve had clients in the past who were dealing with deteriorating foam panels that had started to break down, especially in areas with high humidity like bathrooms or kitchens. Plaster, on the other hand, can withstand moisture and humidity (though proper ventilation is always key).

When it comes to cost-effectiveness, plaster is often more affordable than high-tech soundproofing systems. For example, acoustic plasterboard can be a little more expensive than standard plasterboard, but the price difference is often outweighed by its improved acoustic performance. Additionally, plastering typically doesn’t require expensive machinery or constant replacement, making it a great long-term investment.

Plastering Mistakes to Avoid

While plaster is a highly effective soundproofing material, there are several common mistakes that can undermine your efforts. I’ve worked with clients who thought plastering alone would solve their noise problems, only to find that flanking transmission (where sound travels around barriers) was still an issue. Here’s a quick rundown of some mistakes to avoid:

1. Skipping Surface Preparation: As mentioned earlier, surface preparation is critical. Failing to clean or repair cracks in the wall can lead to poor adhesion and gaps that allow sound to leak through.
   
2. Not Considering Flanking Paths: Sound doesn’t just pass through walls; it can also sneak through floors, ceilings, and even adjoining walls. Ignoring flanking paths is one of the biggest mistakes people make in soundproofing. For instance, when we worked on that apartment in Fitzroy, we had to address the flanking paths between the floor and ceiling before applying the plaster. Without addressing these, the neighbours upstairs would still be able to hear conversations from below. 
3. Using Low-Quality Plaster: Not all plaster is created equal. Using lightweight or non-acoustic plaster for soundproofing can reduce the effectiveness of your efforts. Always use acoustic plasterboard or acoustic plaster designed for soundproofing.
   
4. Ignoring Installation Techniques: Improper installation of plaster can lead to cracks or weak spots that will compromise soundproofing. For example, applying plaster too thick can cause it to crack as it dries, leading to gaps that will let sound pass through.