Learn Hardcore Dutch: Als de buurjongen weer luidruchtig is, doe ik het raam dicht. - If the neighbor boy is noisy again, I close the window.

In Dutch, a clause introduced by a subordinating conjunction (like als, omdat, dat, terwijl, etc.) sends the finite verb to the end of the clause.

Pattern here:

Als
- de buurjongen (subject) + weer luidruchtig (rest) + is (finite verb)

So:

Als de buurjongen weer luidruchtig is, ...

This is normal Dutch word order in a subordinate clause:

[conjunction] + subject + other stuff + verb

Compare:

Omdat hij moe is, ga ik naar huis.
Toen ik klein was, woonde ik in Amsterdam.

In main clauses, the finite verb is in second position; in subordinate clauses, it goes to the end.

Why is it doe ik het raam dicht and not ik doe het raam dicht?

Both are correct — the difference is word order because the sentence starts with the als-clause.

Dutch main clauses follow the verb-second rule (V2): the finite verb must be in second position. The element in first position doesn’t have to be the subject; here it’s the entire als-clause.

Word order skeleton:

[1st position] [2nd position = verb] [subject] [rest]

Applied to your sentence:

1st position: Als de buurjongen weer luidruchtig is
2nd position (verb): doe
Subject: ik
Rest: het raam dicht

So you get:

Als de buurjongen weer luidruchtig is, doe ik het raam dicht.

If you put the main clause first, you’d say:

Ik doe het raam dicht als de buurjongen weer luidruchtig is.

Now ik is in first position, so the usual ik doe order is used.

Why is the present tense used for a future meaning?

Dutch very often uses the present tense in both parts of an als-conditional that refers to the future. English typically uses present + will:

English: If the neighbour’s boy is noisy again, I’ll close the window.
Dutch: Als de buurjongen weer luidruchtig is, doe ik het raam dicht.

Using zal (the future auxiliary) in the als-clause is usually unnecessary and can sound unnatural in everyday speech:

Natural: Als de buurjongen weer luidruchtig is, doe ik het raam dicht.
Possible but more marked: Als de buurjongen weer luidruchtig zal zijn, zal ik het raam dichtdoen. (very formal / heavy, or stressing intention)

So: in conditional sentences with als, stick to the present tense in both clauses unless you have a special reason not to.

What is the difference between als and wanneer here?

Both als and wanneer can translate as if / when, but they have slightly different typical uses:

als
- Very common in spoken Dutch.
- Used for conditions (if) and for repeated or general situations (whenever).
- Fits your sentence perfectly.
wanneer
- Used in questions about time: Wanneer kom je? (When are you coming?)
- Also usable as a conjunction (especially in writing or more formal style) meaning when, more about time than condition.

In your context (a repeated situation, a kind of condition), als is the most natural:

Als de buurjongen weer luidruchtig is, doe ik het raam dicht. (Whenever / if he is noisy again...)

You could say:

Wanneer de buurjongen weer luidruchtig is, doe ik het raam dicht.

but it sounds more formal or bookish in everyday speech.

What exactly does luidruchtig mean, and how is it different from luid or hard?

luidruchtig means noisy — making a lot of noise in an annoying or disturbing way. It often has a negative connotation: someone who is luidruchtig is not just loud, but bothersome.

Compare:

luidruchtig
- noisy, rowdy, boisterous
- Focus on the person/behavior being disturbing.
- De buurjongen is luidruchtig. – The neighbour’s boy is noisy.
luid
- loud (high volume)
- Often about sounds themselves.
- De muziek is luid. – The music is loud.
hard (in audio contexts)
- Also loud.
- Very common for volume:
  - Zet de muziek niet zo hard. – Don’t put the music so loud.

Grammar note: here luidruchtig is a predicative adjective after is, so it has no extra -e.
You’d get luidruchtige with -e if it came before a noun:

De luidruchtige buurjongen. – The noisy neighbour’s boy.

Where can weer go in the sentence, and does its position change the meaning?

In your sentence, weer means again. Its position tells you what is happening again.

Als de buurjongen weer luidruchtig is, doe ik het raam dicht.
- weer is next to luidruchtig.
- Meaning: The boy is noisy again. (His being noisy is repeated.)
Als de buurjongen luidruchtig is, doe ik het raam weer dicht.
- Now weer is next to dichtdoen (close again).
- Meaning: I close the window again. (Closing the window is repeated.)

So both are grammatical, but they say different things:

weer luidruchtig is → he is noisy again.
raam weer dicht (doe) → I close the window again.

Positions like Als de buurjongen luidruchtig weer is are unidiomatic; stick to the positions above.

What is going on with doe ... dicht? Is dichtdoen a verb?

Yes. dichtdoen is a separable verb meaning to close (literally “to do closed”).

Infinitive: dichtdoen
1st person singular: ik doe ... dicht

In main clauses, separable verbs split:

Ik doe het raam dicht. – I close the window.
Ik maak de deur open. – I open the door.

In subordinate clauses, they stay together at the end:

Als hij luidruchtig is, doe ik het raam dicht.
Omdat ik het raam dichtdoe, hoor ik hem niet meer.

So here, doe ... dicht is just the separated form of the verb dichtdoen.

Why is it het raam and not de raam?

In standard Dutch, raam (window) is a neuter noun, so it takes the article het:

het raam – the window
een raam – a window
de ramen – the windows (all plurals get de)

So you say:

Ik doe het raam dicht.

You might occasionally hear de raam in some dialects or non‑standard speech, but in correct standard Dutch it is het raam.

A more formal or old-fashioned synonym is het venster (also neuter: het venster, de vensters).

Could we say sluit ik het raam instead of doe ik het raam dicht?

Yes. Both are possible, with a small nuance:

Ik doe het raam dicht.
- Very common, everyday, slightly more informal.
- Literally: “I do the window shut.”
Ik sluit het raam.
- Slightly more formal or neutral.
- Direct equivalent of English I close the window.

So your sentence could also be:

Als de buurjongen weer luidruchtig is, sluit ik het raam.

meaning essentially the same thing. In speech, het raam dichtdoen is extremely frequent.

Is buurjongen really one word? Why not write buur jongen?

Yes, buurjongen must be written as one word. Dutch generally writes compound nouns together:

buur (neighbour) + jongen (boy) → buurjongen (the neighbour’s boy)

Other examples:

buur
- man → buurman (male neighbour)
huis
- deur → huisdeur (front door)
school
- tas → schooltas (school bag)

Writing buur jongen would mean “neighbour boy” as two separate words, which is incorrect spelling for the compound noun in Dutch. It has to be one word: buurjongen.

Plural:

de buurjongen – the neighbour’s boy
de buurjongens – the neighbour’s boys

Can the order be Ik doe het raam dicht als de buurjongen weer luidruchtig is instead?

Yes, that is also perfectly correct. Dutch allows both orders:

Subordinate clause first:
- Als de buurjongen weer luidruchtig is, doe ik het raam dicht.
Main clause first:
- Ik doe het raam dicht als de buurjongen weer luidruchtig is.

The meaning is the same; the difference is only in emphasis and rhythm. Starting with the als-clause can make the condition feel more prominent. In both cases, remember:

In the als-clause, the finite verb (is) goes to the end.
In the main clause, the finite verb (doe) is in second position.