Noise.
Consideration applies to everyone – so does evidence.

The yardstick is the house rules, the municipality's quiet hours and what is usual in a block of flats. A one-off party is judged differently from repeated noise at night. Construction noise in the building can also be a defect.

• Seek a conversation – neighbours often do not know how loud it is at your place.
• Keep a noise log over several weeks.
• If possible, name witnesses, such as other tenants.
• Write to the management, with the log and a request for action.
• If the defect persists: ask for a reduction or turn to the conciliation authority.

Can I pay less rent because of noise?

If the noise considerably impairs the flat and the landlord knows about it, you can ask for a reduction. Without a log this is hard to show.

Does this also apply to noise from outside?

Hardly for road or rail noise that already existed when you moved in. New burdens, such as a construction site next door, can count.

Art. 257f CO (consideration for residents and neighbours), Art. 259a ff. CO (defects, reduction). Quiet hours: house rules and municipality.