Is Polyfilla Waterproof? (Everything You Need To Know)

Polyfilla is one of the most versatile filler products on the market and can be used for applications on a variety of surfaces.

How well does it stand up to water?

None of the Polyfilla products are fully waterproof, but some specific types of Polyfilla are classified as weatherproof. Weatherproof Polyfilla is meant for exterior use and can withstand rain and snow. Moisture-resistant Polyfilla is also available. It’s great for use in kitchens and bathrooms, but is not intended to stand up to large amounts of water.

Continue reading to learn more about various Polyfilla products. We’ll also talk about Polyfilla’s uses and the differences between Polyfilla and plaster.

Is Polyfilla Resistant To Water?

There are multiple types of Polyfilla. 

Some are considered water-resistant, while others are meant for outdoor use and are classified as weatherproof.

Moisture-Resistant Polyfilla

Just as this product’s name suggests, this type of Polyfilla is a water-resistant filler. It’s meant to fill cracks between surfaces, particularly in areas like bathrooms and kitchens.

To use it, you first need to work the tube between your fingers before removing the cap and squeezing the Polyfilla out in a continuous bead.

Next, level off the filler using a damp cloth or a wet knife. You’ll want to angle the bead so that water drips off of it.

Wipe off the excess Polyfilla before it dries, and then ensure it doesn’t come into contact with water until it’s completely dry. Finally, replace the cap and wash your tools in warm water.

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Multi Purpose Exterior Polyfilla

Because this product is intended for use outdoors, it’s much tougher and can stand up to more moisture than the moisture-resistant Polyfilla.

It’s classified as weatherproof and can withstand rain and snow. However, it’s not fully waterproof. Instead, it’s both water-resistant and water-repellent. 

Suitable for all outside filling projects, the Multi Purpose Exterior Polyfilla takes one hour to set. Once it’s set, it has a weatherproof finish that doesn’t crack or shrink. It also accepts bolts and screws. 

One difference between this product and the moisture-resistant variation is that it’s grey in colour once it has set, rather than white.

To use the weatherproof Polyfilla, squeeze it directly into the crack. Then, use a wet filling knife to smooth it off. If your repair is deeper than 10mm, you’ll want to build up the Polyfilla in layers.

Once dry, sand it down and paint over it if desired.

Polyfilla Uses

Polyfilla is highly versatile and can be used for a variety of projects.

You can repair minor imperfections like cracked paint, nail holes, chipped concrete blocks, and rough wood grain. Polyfilla bonds to masonry, brick, concrete, wood, drywall, and plaster, so it can be used on nearly any surface.

Although Polyfilla can be used for many applications, there are some situations it’s not intended for.

These include floor and deck applications, chinking between logs in log cabins, tuck-pointing on brick, and underwater projects. 

Polyfilla should not be used as a sealant or caulking, either, and it’s not ideal for applications that require flexibility.

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Polyfilla Vs. Plaster

There are multiple differences between Polyfilla and plaster.


Polyfilla is a spackling paste or filler that is cellulose-based. 

Some types of Polyfilla are made from special resins and high-strength cement. Others include ingredients like EVA glue and powdered aggregates.

Plaster is made from water, sand, and lime or gypsum.

Water Resistance

Firstly, Polyfilla is water-resistant, and some types of Polyfilla are even water-repellent as well. 

Meanwhile, plaster is not waterproof–in fact, it’s water-soluble. Plaster is easily damaged when water comes into contact with it.

Ease of Use

There is a Polyfilla product specifically formulated for plaster repair called Polycell Plaster Repair Polyfilla.

It’s a plaster repair powder that’s easy to mix, apply, and smooth out. The product’s description explains that it’s much easier to work with than regular plaster. 


Polyfilla has a better bonding capability than plaster, making it the better choice for small repairs. Using finishing plaster for repairs will also require the use of an adhesive.

Potential Problems

The plaster repair Polyfilla does not crack, shrink, or slump. Unfortunately, these issues are common with plaster.


Plaster tends to be cheaper than Polyfilla.

Although Polyfilla’s cost varies by product, it is usually more expensive per square metre than plaster.


There are many kinds of Polyfilla available, but none of them are fully waterproof.

You can find some types of Polyfilla that are marked as “water-resistant.” These aren’t completely waterproof, but they can still be used in moist environments like bathrooms and kitchens.

Exterior-grade Polyfilla is usually classified as “weatherproof,” meaning that it can stand up to weather like rain and snow. It’s both water-repellent and water-resistant.

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