Learn Hardcore Finnish: Asun vanhassa kerrostalossa, jossa on kapea rappukäytävä. - I live in an old apartment building that has a narrow stairwell.

Because asun already includes the information I, the subject pronoun minä is usually omitted in neutral sentences. You can say Minä asun vanhassa kerrostalossa, but it sounds more emphatic, like I (as opposed to someone else) live in an old apartment building.

So the normal, unmarked version is just Asun … without minä.

Why is it vanhassa and kerrostalossa instead of just vanha kerrostalo?

Both vanhassa and kerrostalossa are in the inessive case (the in-case), which is marked by -ssa / -ssä:

vanha → vanha-ssa
kerrostalo → kerrostalo-ssa

The inessive here means in:

vanhassa kerrostalossa = in an old apartment building

In Finnish, when you say you live somewhere, the place typically goes into the inessive:

Asun Suomessa. – I live in Finland.
Asun Helsingissä. – I live in Helsinki.
Asun vanhassa kerrostalossa. – I live in an old apartment building.

The adjective (vanha) must agree in case and number with the noun it modifies (kerrostalo), so both take -ssa. That is why vanha kerrostalo becomes vanhassa kerrostalossa.

Why is the ending -ssa and not -ssä in vanhassa and kerrostalossa?

The choice between -ssa and -ssä follows vowel harmony:

Front vowels: ä, ö, y → take -ssä
Back vowels: a, o, u → take -ssa
Neutral vowels: e, i → can go with either, depending on the other vowels in the word

The main vowels in vanha and kerrostalo are back vowels (a, o), so they take the back-vowel version -ssa:

vanha → vanhassa
kerrostalo → kerrostalossa

If the word had mainly front vowels, like kylä (village), you’d get:

kylä → kylässä (in the village).

Why does the adjective vanha also change to vanhassa? In English the adjective doesn’t change.

In Finnish, adjectives agree with the noun in:

case (inessive here),
number (singular/plural).

Since kerrostalossa is singular inessive (in the apartment building), the adjective must also be singular inessive:

nominative: vanha kerrostalo – an old apartment building
inessive: vanhassa kerrostalossa – in an old apartment building

So you can think:

noun case changes → the describing adjective must match that case.

What exactly does jossa mean, and why is it in that form?

Jossa is a relative pronoun, roughly in which / where.

It comes from joka (who/which/that) + the inessive ending -ssa:

joka (which/that)
joka
- -ssa → jossa (in which / where)

In the sentence:

Asun vanhassa kerrostalossa, jossa on kapea rappukäytävä.

you can think of jossa as referring back to kerrostalossa:

I live in an old apartment building, *in which / where there is a narrow stairwell.*

Because it means in which, it takes the same in-case (-ssa) as kerrostalossa.

Why is there a comma before jossa in Finnish?

Finnish usually puts a comma before relative clauses, including those starting with joka/jossa/johon, etc.

Asun vanhassa kerrostalossa, jossa on kapea rappukäytävä.

Literally:

I live in an old apartment building, which has a narrow stairwell.

English often allows you to skip the comma (especially with that), but Finnish does not: the comma is standard before jossa in this kind of clause.

Could I say Asun vanhassa kerrostalossa. Siellä on kapea rappukäytävä. instead? What’s the difference?

Yes, that’s grammatical and natural:

Asun vanhassa kerrostalossa. Siellä on kapea rappukäytävä.
- I live in an old apartment building. There is a narrow stairwell there.

Differences:

jossa: explicitly links to kerrostalossa (in which/where); it’s a relative clause.
siellä: means there more generally; it relies more on context.

The original sentence sounds a bit more compact and tightly connected. The two-sentence version is slightly more spoken-style and looser in structure, but perfectly fine.

Why is kapea in its basic form and not something like kapeassa or kapean?

Kapea (narrow) is functioning as a predicative adjective describing the subject rappukäytävä:

(Se) on kapea rappukäytävä. – (It) is a narrow stairwell.

In Finnish, a predicative adjective after olla (to be) is usually in the nominative singular, agreeing with a singular subject:

rappukäytävä – stairwell (nominative)
on – is
kapea – narrow (nominative)

So kapea rappukäytävä is like saying a narrow stairwell as the thing that exists. You would not put kapea into a case here; the location is already expressed by jossa (in which / where), not by the adjective.

Why is rappukäytävä in the basic form? Shouldn’t it also have -ssa if the stairwell is in the building?

Rappukäytävä is the subject of the verb on in the relative clause:

jossa on kapea rappukäytävä
→ in which / where there is a narrow stairwell

So grammatically, the structure is:

subject: kapea rappukäytävä (a narrow stairwell)
verb: on (is)
location: encoded in jossa (in which)

The in-ness is already in jossa (inessive case), so rappukäytävä itself stays in the nominative. You don’t need to mark the location twice.

Does asun mean I live or I am living? English makes a difference.

Finnish does not distinguish these two aspects the way English does. The present tense asun can mean:

I live (there in general / permanently)
I am living (there temporarily)

Context usually clarifies whether it’s permanent, semi-permanent, or temporary. If needed, Finnish can add adverbs or time expressions (e.g. nyt, tällä hetkellä, tilapäisesti) to clarify, but the verb form itself is the same.

What exactly does kerrostalo mean? Is it the same as “apartment”?

Kerrostalo is a compound noun:

kerros – floor, storey
talo – house, building

Together: kerrostalo ≈ a building with multiple floors, usually an apartment building / block of flats.

It refers to the whole building, not an individual apartment. An apartment inside it is typically:

(kerros)asunto – apartment / flat

So vanhassa kerrostalossa is in an old apartment building, not in an old apartment.

Could I say Asun vanha kerrostalossa without changing vanha?

No, that would be ungrammatical.

Because kerrostalossa is in the inessive case, the adjective must also be in the inessive:

❌ vanha kerrostalossa
✅ vanhassa kerrostalossa

Adjectives modifying a noun have to agree in case and number:

iso talo – big house (nominative)
isossa talossa – in a big house (inessive)
uusissa taloissa – in new houses (plural inessive)

The form vanha kerrostalossa sounds as wrong to a Finn as “I live in old apartment building” without an sounds to an English native – clearly broken.

Is there any difference between saying Asun kerrostalossa, jossa on kapea rappukäytävä and Asun vanhassa kerrostalossa, jossa on kapea rappukäytävä?

Yes, mainly in how specific and descriptive you are:

Asun kerrostalossa, jossa on kapea rappukäytävä.
– I live in an apartment building where there is a narrow stairwell.
(no information about the age of the building)
Asun vanhassa kerrostalossa, jossa on kapea rappukäytävä.
– I live in an old apartment building where there is a narrow stairwell.
(adds the extra detail that it’s old)

Grammatically, both are the same structure; vanhassa just adds an additional piece of information.