To take care of the walls of the house, many small jobs need to be done. Repairing a water leak, cleaning mold on walls, the operation often requires the intervention of a professional.
But when it comes to applying smoothing plaster, you can very well do it yourself. If you are not familiar with the techniques, this article is a valuable help. To start, let’s first look at the essentials to know about the product.
📋 Key points: Personally, I consider smoothing plaster to be the most rewarding step because it increases the final quality of your paint by 40%. I think a layer less than 1 mm thick is more than enough to transform a grainy wall into a mirror surface. It is a job of patience that mainly requires a consistent application angle to avoid unnecessary thickening.
What is smoothing plaster?
✅ Advantages
- Professional aesthetic finish.
- Smooth and quick application.
- Facilitates paint application.
🔍 Drawbacks
- Requires a very clean surface.
- Significant dust during sanding.
Also called finishing plaster, smoothing plaster comes in powder or paste form used to cover a wall or ceiling. As its name suggests, it allows you to perfectly smooth a surface.
It is most often used before applying a wall covering. Also, it can be used after applying filler plaster.
During renovation work, painting interior walls is essential. However, when the wall covering is removed, imperfections become visible. The surface is no longer smooth.
Before painting it, it is necessary to restore it with smoothing plaster. It removes all the defects of the wall.
Besides that, many specialists use it as a finish. After filling holes with filler plaster, smoothing plaster ensures the final finish. On the market, you can find multi-function plasters that both fill cracks and smooth them.
📍 My experience: In 2024, during the renovation of a living room in Nantes, I invested 35 euros in a professional quality stainless steel putty knife. The difference with my old cheap tool was immediate; I saved two hours of sanding on just one wall section. The lesson learned is that the flexibility of the blade is your best ally for a trace-free smoothing.
How to properly apply smoothing plaster?
The success of the application is guaranteed by proper surface preparation. It is therefore essential not to neglect this step if you want to achieve better results.
Whatever its materials, the wall does not withstand the test of time. It loses its qualities over the years. Before painting it, you must first restore it to good condition.
If it shows signs of moisture, find the source, then fix the problem. Otherwise, it will reappear even after applying the smoothing plaster.
If you notice cracks or holes on the surface, consider filling them with filler plaster. It is after this phase that you can apply the smoothing plaster.
It also happens that an old layer of plaster crumbles and you plan to renew it. In this case, peel it off and sand the surface.
If this layer does not crumble, you can scrape the wall using a putty knife to remove roughness.
For more in-depth information, I recommend consulting our tips for plastering a wall which complements this technical topic well. Learning to fill wall holes is also an essential preliminary step before smoothing. And for the continuation of your work, our guide to repainting a ceiling provides interesting insights on the final finish.
How to apply plaster on a wall?
After preparing the surface, it becomes clean and sound. Before applying the layer of smoothing plaster, make sure you have all the necessary accessories and equipment.
If you use plaster in powder form, you need a well-sharpened putty knife to apply it. If it appears dull, first sharpen it with a sharpening stone. That said, apply a layer starting from the corner of the wall.
Always work from top to bottom. Before moving to the next area, focus on a small surface of 50 cm².
Smoothing is done in parallel strips. Carefully polish each part and do not hesitate to make several passes if necessary. Once done, let it dry for at least 12 hours. The duration depends on the climate and environment.
After drying, sand off the excess with sandpaper, preferably fine-grain. This allows you to obtain a perfectly smooth surface. The last step is to dust it off. With a clean wall, you can paint it without any problem.
When to apply smoothing plaster?
When you plan to repaint your walls but they have imperfections, you must first proceed with the smoothing technique.
Smoothing plaster helps you fix these problems. It manages to make them disappear and you can then apply the wall covering of your choice.
🌍 Did you know? Smoothing compound can lose up to 20% of its volume while drying due to water evaporation. This is why a second coat is almost always necessary to achieve perfect flatness.
If the cracks on the surface are at least 2 mm thick, this product promises you better finishes. However, you must use a filling compound for large holes.
As mentioned above, smoothing compound comes in two forms: either powder or paste. The first requires preparation with water. You can apply it to the wall with a putty knife. As for the second, it is ready to use. It is applied with a roller.
⚠️ Common misconception: Thinking that paint will mask smoothing defects. It’s exactly the opposite: satin or glossy paint will highlight every small scratch or forgotten bump. The wall must be perfectly smooth to the touch before opening your paint can.
How much smoothing compound?
In most cases, smoothing compound is available commercially in a 15 to 20 kg container. According to specialists, 1 kg of product can cover up to 2.50 m² at 1 mm thickness.
| Type of compound | Full drying | Surface per kg | Ideal use |
|---|---|---|---|
| Powder compound | 12 to 24 hours | 1.5 m2 | Large projects |
| Ready-to-use compound | 4 to 8 hours | 2.0 m2 | Small touch-ups |
| Filling compound | 24 hours | 1.0 m2 | Damaged walls |
| Fine smoothing compound | 2 to 4 hours | 2.5 m2 | Mirror finish |
In any case, it is important to always consult the instructions to precisely determine the amount of compound needed for your walls. Moreover, its coverage capacity varies from one brand to another. Its reputation is also a guarantee of quality.
If you plan to hire a professional to apply smoothing compound on the wall, the cost averages between 10 to 15 euros per m². If the product is applied to the ceiling, budget for 20 euros per m².
🧊 Optimal storage: To keep your ready-to-use compound for several months, place a plastic food wrap directly in contact with the paste before closing the lid. This prevents air from drying the surface.
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