1.Has he obtained sanction/approval from the local municipality for the said extension of kitchen?
2. If no, then lodge a complaint before the local municipality complaining against the said illegal construction,
3. Lodge a police complaint also for the said illegal construction without any sanction,
4. If there is no action taken by the municipality or police, you can file a writ petition before the local High court against police and municipality inaction praying for a stay order till the matter is disposed off.