Learn Hardcore Japanese: watasi no ie ha hurui desu.

の is the genitive (possessive) particle in Japanese. It links two nouns, showing that the first noun possesses or relates to the second. So 私の家 means “my house.”

What role does は play after 家?

は is the topic‐marking particle. By saying 私の家は…, you’re setting “my house” as the topic of the sentence—literally, “As for my house, …” It signals what you’re talking about before giving information about it.

Why is 古い placed before です? Could it go after?

In Japanese, adjectives come before the copula です. Here, 古い is an i-adjective, so the structure is:
Adjective (古い) + Copula (です)
You cannot swap them; saying です古い would be ungrammatical.

What kind of adjective is 古い, and why is です needed with it?

古い is an i-adjective, which can directly modify nouns (e.g., 古い本 “old book”) or predicate a sentence. Adding です makes the statement polite and more formal. Without です, 私の家は古い is still correct but more casual.

Can I omit 私の and just say 家は古いです?

Yes—if it’s clear from context whose house you mean, you can drop 私の. Then 家は古いです simply means “The house is old,” with an implied subject based on context.

What’s the difference between 家 read as いえ versus うち here?

いえ (ie) refers more to the physical building.
うち (uchi) often means “home” or “my place” with a softer, more personal nuance.
You could say 私のうちは古いです, but うち already implies “my,” so うちは古いです is enough in casual speech.

Why not use the subject‐marking particle が instead of は?

Using が (私の家が古いです) focuses on identification or introduces new information: “It’s my house that’s old.” It’s less common for a simple descriptive statement. は is preferred for stating attributes of a known topic.

How would this sentence look in plain (casual) form?

Drop the polite copula です:
私の家は古い
This is fine in informal conversation or writing.

Are there other ways to say “my house is old” in Japanese?

Yes. For example:
• 私の家は古くて… (my house is old and …) – to connect more info
• うち、古いんだ。 (casual) – “My place is old, you know.”
• 実は家がかなり古いです。 (polite, adds emphasis) – “Actually, the house is quite old.”