Is Polished Plaster Waterproof?

by | Jan 18, 2023 | Polished Plaster

Updated 31/08/2023

Is polished plaster waterproof? The quick answer is no. However, the plaster can still be used in swimming pool, spa, and bathroom designs. But there are some considerations.

How Can You Make Polished Plaster Waterproof?

Venetian plaster (also called polished plaster) can be made water-resistant but not waterproof. What’s the difference?

“Waterproof” usually means that a material is impervious to water. Water is not able to go through the material. The material may be waterproof on its own or may require a sealant to make it waterproof. The seal creates a barrier that keeps water out.

On the other hand, “water-resistant” means that a material repels some water but not all. Water-resistant is very different from waterproof. Materials that are water-resistant will repel water to a point. After some time, water may soak or seep through the material.

When it comes to polished plaster, it can be made water-resistant with the addition of topical sealants. These can be applied to the plaster’s surface; however, they will not make the surface waterproof.

For this reason, Venetian plaster is not the right material for a shower enclosure or a space where large amounts of water will hit the plaster surface. However, the polished plaster can be applied to a space that may experience occasional water splashes. But then there are certain requirements to consider.


Why Isn’t Polished Plaster Waterproof?

Polished plaster in an unsealed and unwaxed state is very porous, very much like natural stone. Some finishes are more porous than others. There’s a general rule that says the more texturized the polished plaster, the more porous it is. Textured polished plaster such as Pitted, Granito, and Dragged tend to be more porous, while Marmorino Spatula, Mamorino, and Smooth are less porous.

To make polished plaster water-resistant, it’s necessary to use waxes and sealants to help provide them with the protection they need and to keep the plaster in good condition. When these surfaces are waxed or sealed, they become low maintenance. All it takes to clean these surfaces is a damp cloth and warm soapy water. However, the Venetian plaster surfaces are still not waterproof, even with sealants. But with the added protection, it is possible to use polished plaster in areas where water may be splashed onto the plaster.

The main reason that polished plaster is not waterproof is that it’s made with lime. Lime is a natural material that gives polished plaster its breathable quality. While this quality can be a benefit in some cases, when used in wet areas, without sealants, the plaster can become damaged.


Is it Possible to Use Venetian Polished Plaster in Wet Environments?

Yes, and it’s a great choice, too. Venetian polished plaster is breathable and has a high pH, making the plaster inhibit the growth of mould, mildew, and bacteria common in damp, wet environments.

You may use a solvent-based paraffin wax to protect the surface; however, it’s best to first ply a water-repellent product first and then apply the wax over this.

However, it’s best to consult with a Venetian polished plaster expert to get their advice on how to make the surface waterproof.


Is Venetian Polished Plaster Appropriate for Wet Environments?

The answer is yes. Lime-based materials, such as polished plaster, are breathable and have a high pH. These qualities make polished plaster great for wet environments. For instance, the high pH keeps mould, mildew, and bacteria from growing. These microbes are all common in humid environments.

However, we must warn you that polished plaster is not appropriate for areas that are constantly bombarded with large amounts of water, such as a shower. It is possible to use polished plaster in the shower, but it takes quite a lot of work and investment to ensure the plaster won’t let water through.


What are the Benefits of Using Polished Plaster in Wet Environments?

There are several benefits to using polished plaster in wet environments, including:


Venetian Plaster is Easy to Maintain

Unlike tiles that can develop mould and discoloration in the grout, Venetian plaster doesn’t have grout lines. The plaster is then much easier and faster to maintain than tiles. Even minor scuffs are easy to remove with mild detergent and soapy water.


Venetian Plaster is a Natural Material

When plasterboard is used in a wet environment, it must be treated and painted. What’s more, bathroom wall paint can emit VOCs (volatile organic compounds) that can be irritating to the airways and to anyone who has multiple chemical sensitivities.

What’s more, wall paint and other wall treatments must dry completely before additional work can be done on the room. On the other hand, polished plaster is made with natural ingredients that don’t release VOCs.


Polished Plaster Resists Mould, Mildew, & Bacteria

Lime, the main ingredient in polished plaster, has antimicrobial properties that help reduce the growth of mould, mildew, and bacteria. You won’t have to deal with mould and other microbes, which is especially beneficial for anyone who has a mould allergy or tends to become sick with bacterial infections.


Venetian Plaster is Durable

Polished plaster is one of the most durable materials that can be used on a home’s interior. Plasterboard, for instance, can crack, become dented, or be damaged with holes.

Venetian plaster hardens slowly, so it’s less susceptible to cracking. If it’s well-maintained, polished plaster can last decades or centuries.


Polished Plaster Can Be Applied Over Old Tiles

Most bathroom renovations involve the removal of old tiles and then retiling the walls and floors. However, you won’t have to do any of that work if you go with polished plaster.

Venetian polished plaster can be applied directly over existing wall tiles. The material is plastered onto the surface of the tiles, and all deformities and irregularities are covered. You can then go faster with your bathroom renovation and end with a style and look you prefer.


Summing It Up

While polished plaster is not waterproof, it can be made water-resistant with the addition of sealants and wax. Venetian polished plaster can’t be used in a shower; however, it can be used in other parts of a wet area, including around sinks and more.

So, why not consider polished plaster for your pool area, spa, or bathroom? If you want a luxurious, stunning wall treatment, you can’t do better than polished plaster!


Q: Can polished plaster be used in showers?
A: While possible, it’s not recommended due to its limited waterproofing capacity.

Q: Is polished plaster scratch-resistant?
A: While it’s durable, sharp objects can still cause scratches or damage.

Q: Can I apply polished plaster myself?
A: It’s advisable to hire a professional to ensure proper application and finish.

Q: Does polished plaster require regular maintenance?
A: Yes, regular dusting and gentle cleaning are necessary to preserve its beauty.

Q: Can polished plaster be used for exterior surfaces?
A: No, it’s designed for interior use and may not withstand outdoor conditions.

Q: Can polished plaster cover uneven wall surfaces?
A: Yes, its textured nature can help conceal minor imperfections.

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