Im Mietvertrag steht, dass wir den Hausmeister informieren müssen, wenn der Rauchmelder piept.

In the rental contract it says that we have to inform the caretaker if the smoke detector beeps.

Breakdown of Im Mietvertrag steht, dass wir den Hausmeister informieren müssen, wenn der Rauchmelder piept.

• wir: we
• dass: that
• im: in the; (masculine or neuter, dative)
• den: the; (masculine, accusative)
• informieren: to inform
• der: the; (masculine, nominative)
• müssen: must / have to
• der Mietvertrag: the rental contract
• stehen: to say (be written)
• der Hausmeister: the caretaker
• wenn: if/when
• der Rauchmelder: the smoke detector
• piepen: to beep

Questions & Answers about Im Mietvertrag steht, dass wir den Hausmeister informieren müssen, wenn der Rauchmelder piept.

Why does stehen mean “to say/it states” here? I thought it meant “to stand.”

In German, stehen can be used idiomatically for written information: Im Mietvertrag steht, dass … = “The rental contract states that …”.
It’s very common with documents, signs, instructions, etc. (similar to In der Zeitung steht … = “It says in the newspaper …”).

What’s the grammar of Im Mietvertrag? Why im?

im is a contraction of in dem.

• der Mietvertrag is masculine → dem Mietvertrag (dative) after in when it means “in/within” (location, not motion).
  So Im Mietvertrag = in dem Mietvertrag (“in the rental contract”).

Why is there a comma before dass?

In German, a subordinate clause introduced by dass is set off by a comma.
So Im Mietvertrag steht, dass … must have that comma.

Why does the verb go to the end in dass wir den Hausmeister informieren müssen?

Because dass introduces a subordinate clause, and in subordinate clauses the conjugated verb goes to the end (or, with verb clusters, to the very end of the clause).
Here you have a two-verb cluster: informieren müssen. The finite verb is müssen (conjugated for wir) and it ends the clause.

Why is it den Hausmeister and not dem Hausmeister?

Because informieren takes a direct object in the accusative: you inform someone (jemanden) about something.

• der Hausmeister (nominative)
• den Hausmeister (accusative)
  So wir informieren den Hausmeister = “we inform the caretaker.”

Is Hausmeister the same as a landlord?

Not necessarily. der Hausmeister is typically the building’s caretaker/maintenance person (often handling repairs, checks, small maintenance).
der Vermieter is the landlord (the person/company you rent from).

What does müssen add here compared to just informieren?

müssen expresses obligation/requirement: “we must / we are required to.”
Without it (… dass wir den Hausmeister informieren, …) it would sound more like a general statement (“that we inform/notify…”), not explicitly a requirement.

Why is there another comma before wenn?

Because wenn der Rauchmelder piept is another subordinate clause, and subordinate clauses are separated by commas.
So the structure is: main clause + dass-clause + wenn-clause.

Does wenn mean “if” or “when” here?

wenn can mean both. In rules/instructions like this, it often means “when(ever)” in the sense of “in the event that / whenever”:

• “notify the caretaker if/whenever the smoke alarm beeps.”

Why is the verb at the end in wenn der Rauchmelder piept? It looks normal (verb second).

In this wenn clause, the verb is actually in the “subordinate clause position,” but with a simple present-tense clause it can look like normal verb-second order in English.
German rule: in wenn-clauses, the conjugated verb goes to the end of that clause. Here the clause is short: wenn der Rauchmelder piept (subject der Rauchmelder, verb piept at the end).

What case is der Rauchmelder, and why?

der Rauchmelder is the subject of piept, so it’s in the nominative:
der Rauchmelder piept = “the smoke detector beeps.”

Why is piept in the present tense? Shouldn’t it be future?

German commonly uses the present tense for future situations, especially in conditional/temporal clauses:
wenn … piept = “if/when it beeps” (future meaning is understood from context).

Could the sentence be phrased differently, and would the word order change?

Yes. For example:

• Wenn der Rauchmelder piept, müssen wir den Hausmeister informieren.
  Here the wenn clause is moved to the front. Then the main clause starts with müssen because German keeps verb-second order in main clauses: the fronted clause counts as position 1.