Learn Hardcore Japanese: yuka ni ha hurui kaapetto ga siite atte, sukosi yogorete iru. - An old carpet has been laid on the floor, and it’s a bit dirty.

床に: に marks the location – “on the floor / at the floor”.
は: marks 床に as the topic of the sentence – “as for on the floor… / regarding the floor…”.

So 床には roughly feels like:

床には → “As for the floor / On the floor (in particular), …”

Nuance:
Using には instead of just に often implies some contrast or focus:

Maybe other places in the room don’t have a carpet, but the floor does.
Or the speaker is now “zooming in” to talk specifically about what’s on the floor.

You could technically say:

床に古いカーペットが敷いてあって…

That would be more neutral: “There is an old carpet on the floor…”, without the slight “as for the floor…” feeling that 床には has.

Why is カーペット marked with が and not は?

In this sentence, カーペット is the subject of the verb phrase 敷いてあって (“is laid / spread out”), so it takes が:

古いカーペットが敷いてあって
→ “An old carpet is laid (there)…”

If we changed が to は:

古いカーペットは敷いてあって…

then 古いカーペット would become the topic, and the nuance would shift to “as for the old carpet…”. That can sound like:

We are already talking about this carpet (known information) and now commenting on it.

With が:

古いカーペットが presents the old carpet as new information: “there is an old carpet (there)”.

So:

床には → topic (“as for the floor…”)
古いカーペットが → subject (“an old carpet (as subject) is laid there”)

What exactly does 敷いてあって mean, and why not just 敷いてある?

Breakdown:

敷く = “to spread / lay out” (e.g. carpet, futon, mat)
敷いてある = 敷く (te-form) + ある

Verb + てある has a special meaning:

It shows the resulting state of a deliberate action done by someone, and that state still remains.

So:

カーペットが敷いてある。
→ “A carpet has been laid (and is there now).”
→ Implication: someone laid it there on purpose, and it’s still laid out.

Now, in your sentence we have:

敷いてあって、少し汚れている。

Here あって is just the て-form of ある, used to connect this clause to the next one (少し汚れている).
So literally:

敷いてあって、少し汚れている。
→ “(It) is in the state of having been laid there, and (it) is a little dirty.”

Natural English:
“There’s an old carpet laid on the floor, and it’s a little dirty.”

If you made it a standalone sentence, you would typically say:

床には古いカーペットが敷いてあります。
(polite)

But when you connect it with 少し汚れている, you use the て-form:

敷いてあって、少し汚れている。

Could we say 敷かれていて instead of 敷いてあって? What’s the difference?

Yes, you can say:

床には古いカーペットが敷かれていて、少し汚れている。

Here’s the difference in nuance:

敷いてあって (敷く + てある):
- Focuses on the result of a purposeful action.
- Implies: someone laid the carpet there intentionally, and it remains laid out.
- Very natural for things like carpets, futons, tablecloths, etc.
敷かれていて (passive, 敷かれる
- ている):
- Grammatically fine; simply describes the carpet as “being laid/spread” in a more neutral, passive way.
- Less emphasis on the idea “someone purposely set it up and it’s left like that”.

In this context, 敷いてあって sounds more natural and more typical, because a carpet on a floor is usually seen as something that has been put there by someone and remains there.

Why use 汚れている instead of the adjective 汚い?

Both can describe something dirty, but the nuance is different:

汚い = an adjective meaning “dirty / filthy / messy”.
- 少し汚い。 → “It’s a bit dirty.” (describing a quality)
汚れている = 汚れる (intransitive verb “to become dirty”) + ている
- Literally: “is in the state of having become dirty.”
- Describes a resulting state after a change.

So:

少し汚れている。 → “It has gotten a little dirty / It’s a little dirty (as a result of getting dirty).”

Nuance:

汚れている often suggests:
- It used to be cleaner,
- Something happened to make it dirty (time + process).
汚い is more static: it just says “dirty” as a characteristic, without that “it has become dirty over time” feeling.

In this sentence, 汚れている nicely matches the idea of:

A carpet that has been there for a while and has become a bit dirty.

Why do we use いる in 汚れている when a carpet is not alive? Shouldn’t it be ある?

The いる vs ある distinction applies only to the existence verbs:

いる = “to exist (for animate things)”
ある = “to exist (for inanimate things)”

But in 汚れている, いる is not the existence verb. It is the auxiliary used in Verb + ている, which expresses aspect (ongoing action or resulting state).

Pattern:

汚れる (to get dirty, become dirty)
汚れている (is dirty / is in a dirty state, as a result of becoming dirty)

This ている form is used regardless of whether the subject is animate or inanimate.

Examples:

ドアが閉まっている。
→ “The door is closed.” (door is inanimate, but we still use ている)
窓が割れている。
→ “The window is broken.” (resulting state)

So 汚れている is perfectly correct for a carpet. You would never use 汚れてある here; てある attaches directly to an action verb (like 敷く) to mean a deliberately caused state.

What does the comma and the 〜て connection do in 敷いてあって、少し汚れている?

The comma (、) plus the て-form (敷いてあって) is simply linking two clauses that share the same subject (the carpet):

Clause 1: 古いカーペットが敷いてあって
→ “there is an old carpet laid (on the floor)”
Clause 2: 少し汚れている
→ “(it) is a little dirty”

So:

古いカーペットが敷いてあって、少し汚れている。
→ “There’s an old carpet laid (on the floor), and it’s a little dirty.”

The て-form here can imply:

simple addition (“and”),
slight cause/result or background (“with it laid there, it’s a little dirty”).

If you broke it into two sentences, you’d get:

床には古いカーペットが敷いてある。少し汚れている。

The meaning is almost the same; joining them with 〜て just makes it flow as one smooth description of the same object.

Can I say 床の上に instead of 床に? Is there any difference?

Yes, you can say:

床の上に古いカーペットが敷いてあって、少し汚れている。

Both 床に and 床の上に are acceptable.

Nuance:

床に:
- Very common. Often understood as “on the floor” in this kind of context.
- Shorter and more natural in everyday speech.
床の上に:
- Literally “on top of the floor”.
- Slightly more explicit and sometimes a bit more formal or descriptive.

In most everyday descriptions of rooms, 床に is completely natural and usually preferred.

Does 敷いてあって imply that someone intentionally put the carpet there?

Yes. That’s a key nuance of Verb + てある.

敷いてある / 敷いてあって:
- Describes the result of a deliberate action.
- Implies that someone laid the carpet there on purpose, and it’s still in that state.

Compare:

カーペットがある。
→ “There is a carpet.” (just existence; no implication of action)
カーペットが敷いてある。
→ “There is a carpet laid (out).”
→ Sounds like: someone laid it out, maybe as part of preparing the room.

So in your sentence, the combination of 敷いてあって and 汚れている suggests:

This is a carpet someone put down to use, and now it has become a bit dirty over time.

Is the sentence talking about a current state, or a past action, or a habit?

Grammatically, it describes a current state:

敷いてあって → the carpet is in a state of having been laid out.
汚れている → the carpet is in a state of having become dirty.

Japanese 〜ている / 〜てある often focus on states that are true now, which may be the result of some past action.

So the sense is:

“(Right now, in this room) there’s an old carpet laid on the floor, and it’s a little dirty.”

It is not describing a habit (like “whenever I go there, there is an old carpet and it’s dirty”) nor a simple past event; it’s a present descriptive snapshot.