ᐅ Plastered chimney over 5 years old without sealing – what should be done?

Hello,
in 2019, we built a holiday home where a chimney was installed in front of the wooden house. The chimney was nicely painted white by the construction company, but only below the eaves. Above the eaves, the plaster was so light that we didn’t notice it wasn’t painted there. Now it has been exposed to the Baltic Sea air for more than 5 years and is turning gray, and I can also see some small cracks.
My question: after this time, how should it be sealed? Would a simple pretreatment with primer followed by facade paint be sufficient?
Thanks in advance for your advice!

Ulfert2025 schrieb:

How will it be sealed after this time?

It won’t be sealed at all. Paint does not seal anything. You can paint it, of course. Paint type and application instructions depend on the answers to a few questions:

- Photos?
- Material?
- What kind of cracks? How large?

Hello and thank you for your reply.

How does the paint protect the plaster without sealing the pores?
Photos are attached; the cracks can be seen in one of the pictures. I would describe them as hairline cracks.
Unfortunately, the material is not clear from the building description, it only says “plastered.”

Regards, Ulfert

Ulfert2025 schrieb:

How does the paint protect the render without sealing the pores?

The paint makes the render look attractive. You can also buy colored render that doesn’t need to be painted at all. Paint is mainly about appearance – it can help with thermal insulation, for example by reducing algae growth. If you consider that as “protection,” then the paint does provide it.

For example, silicate paint on mineral render only mineralizes the surface without sealing the pores. This ensures the render remains vapor-permeable. It also slows down water penetration into the render but does not completely prevent it. Other paints have different effects. However, paint can’t really do more than provide color, algae/dirt protection (which lasts only for a limited time), and improved rainwater beading.

Unfortunately, I can’t see the small crack at all on my phone.

If it is a mineral render, I would simply clean it and apply a mineral-based paint (silicate). Then you can get a better idea of the crack’s exact condition. It could also be a construction defect appearing now – or possibly the result of frequent use of the fireplace, causing minor cracking due to heat.

Ok, then we’ll let the plaster breathe and use a silicate paint. This is probably better for a chimney exposed to changing conditions.
Alpina, on the other hand, promotes the silicone facade protection as highly water-repellent. Which usually also means it doesn’t release moisture that quickly.