ᐅ Issue with Rafters / Eaves – Exterior Paint

Hello,
about 4 years ago, the eaves (rafters and boards) of the newly built semi-detached house were painted with the white satin finish Venti paint from Südwest. For about 1 year now, black spots have appeared on the white paint - see attached pictures.

Questions:
1.) Was the wrong white paint used, not weather-resistant, etc.?
2.) What could the black spots be – weathering, algae, etc.?
3.) What is the recommended approach to fix this? Sanding and repainting?

Regards,
Michael

1) The paint could have been better. Was the primer missed?
2) Weathered, with substances from the wood bleeding through.
3) Repaint, remove loose paint first; otherwise, sanding is needed. Use Consolan.

Thanks for the information. I cannot say whether a primer was used. The wood was probably already pretreated by the master carpenter. The plasterer applied the final coat with the white paint. Could this still be a warranty issue after 4 years?

Here you can see the white primer applied by the carpenter on the roof overhangs before the satin white ventilation paint was applied.

No. No warranty. This was simply window paint; it can’t do more than that.
Primer is used to prevent resin from softwood, etc., from bleeding through the paint, which is always visible with white paints. With red or brown paints, this is usually omitted, and with gray, unless it is specifically shark gray, it is also not used.
The paint I recommend, Konsolan, works differently — it penetrates deeply into the wood and bonds securely. This could also be achieved with paint, but then the first coat must be heavily diluted. Who does that nowadays? Too expensive and too time-consuming. Just apply the paint as is. The customer doesn’t want to go broke over a few boards.

Did you take the pictures at my place?
It looks the same for me. As long as it doesn’t cause any real damage, I’m not going to do anything for now.