Removing concrete pimples: surface preparation for Renovlies

Handed over as wallpaper-ready? Run your hand over it

Many new-build owners only discover it after the keys are handed over: the walls are officially "wallpaper-ready" according to the handover report, but when you run a flat hand across the surface you can feel dozens of tiny bumps. Those are concrete pimples: hard little imperfections in the concrete that form during pouring or as the wall dries and shrinks.

To the eye they're barely noticeable. But as soon as you apply Renovlies or wallpaper, they show through the surface as bumps. With raking light on them it becomes a sea of shadows. That's why removing concrete pimples is always the first step in every new-build project we take on.

What exactly are concrete pimples?

Concrete pimples are small to medium-sized protrusions in concrete surfaces, usually 1-5 mm in size. They're rock hard and firmly embedded in the concrete. The cause lies in the construction process: during pouring, air bubbles or cement particles can stick to the formwork, or the wall shrinks slightly as it cures, pushing small pieces outward.

What "wallpaper-ready" actually means varies from builder to builder. Strictly speaking it means the wall no longer needs to be plastered, but not that it's smooth enough for a clean wall finish. Read our explanation of wallpaper-ready versus Renovlies for details on what you should really expect from a new-build handover.

Why are concrete pimples a problem for Renovlies?

• Visible through the Renovlies: especially with thinner weights (120-150 grams), the bumps show up in the final result.
• Early damage to the Renovlies: a hard lump can push the Renovlies up and cause it to tear or come loose at that spot.
• Higher material use: to mask the bumps, many DIYers switch to a thicker Renovlies variant or apply extra adhesive. A waste, because the problem is underneath.
• Unnecessarily thick paint layer: to paint over the imperfections, extra coats of emulsion go on top. That doesn't really hide the problem.

How do we remove concrete pimples?

Our approach is always the same, whether it's a 70 m² apartment or a detached new-build of 200 m²:

1. Inspect the entire wall with raking light: a work lamp held at an angle to the wall reveals every bump and pit.
2. Machine sanding: with a professional sander with dust extraction, we remove the vast majority of the pimples in a single pass.
3. Grinding on harder spots: if any hard bumps remain, we use a grinding tool to bring them level with the rest.
4. Filling pits with filler: small dents are filled with filler compound. Once dry, we sand them smooth.
5. Priming/sealing: a primer evens out the suction of the wall so the Renovlies bonds evenly everywhere.
6. Final check with raking light: only when the wall looks flat and closed everywhere does the Renovlies go on.

For some DIYers, sanding alone is enough. But anyone who works honestly knows: good surface preparation is 70% of the final result. Read our guide on saving costs with Renovlies. Cutting corners on preparation always costs you more in the end.

DIY or leave it to the professionals?

In theory you can do it yourself. In practice it's incredibly dusty, heavy work and it's hard to get the entire surface even, especially with an ordinary hand sander without dust extraction. For a single small wall it's worth considering. For an entire floor, it's not.

With us, this is a standard part of the job. One team comes in, does the preparation, fills, sands, applies Renovlies and paints. No handover issues, no "well that was the previous contractor." Read our background piece on why a Renovlies specialist makes the difference. With our 100% coverage guarantee you know that imperfections won't show through in your final finish later.

Smooth walls start beneath the surface

A great Renovlies result is never just a matter of choosing the right wallcovering. It's a matter of what's underneath. We always invest the time in surface preparation, because that's what makes the difference between a great result on handover day and a great result ten years down the line.

Request a free, no-obligation quote: we'll come by, assess your walls with raking light and give you a fair price for a quality, professional result.