ᐅ Apply an additional coat of bituminous waterproofing to the base coat of the plaster.

Created on: 11 Jan 2026 20:49
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mariusf
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mariusf
11 Jan 2026 20:49
Hello everyone,

At my new build, the plastered base was protected with a thick bitumen coating three weeks ago. The coating extends noticeably above ground level in some areas.

Can I simply paint the base, including the coating above ground level? Or do I need a primer or something similar?

Best regards,
Marius
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nordanney
11 Jan 2026 21:42
mariusf schrieb:

Can I simply paint the base including the coating above ground level? Or do I need a bonding agent or something similar?
Painting is generally not possible on the foundation—only with roof coatings suitable for bitumen. However, that won’t help for the rest of the base (how exactly is it supposed to be further treated?). You could try Weber.prim 404 and then paint over it. Alternatively, apply Weber.tec Superflex D 24 and then paint. It’s basically a sealing slurry, adheres well, and can be painted normally afterward. But what is the plan for the rest of the base? I think it will always look somewhat awkward.
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mariusf
11 Jan 2026 22:03
Hello @nordanney,

thank you very much for the quick response. The base has been completely plastered and only needs painting now. Unfortunately, during the preparation for the paving, the bituminous waterproofing was applied too high.

Cross-section of a wall construction with silicone resin render on top and finished base plaster below

Attached is a sketch of the facade structure. I would like to paint the black bituminous thick coating and the light gray base.
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MachsSelbst
11 Jan 2026 22:11
In the end, you only have two options. Either make the uneven thick coating clean and accept the edge as it is. A properly applied coating doesn’t look that bad.

Or you cut the thick coating cleanly down to the base plaster with a cutter, scrape it off using some of the plaster, and redo the base plaster. At the same time, you can cover the “old” base plaster with decorative stone plaster (what a sentence...).

That’s how I did it. Decorative stone plaster is actually the best option—it doesn’t show dirt and is water-repellent to a certain extent.

You can’t paint over bitumen permanently; nothing will stick.