Learn Hardcore Spanish (Latin America): Espero que hoy no haya temblor, porque el rascacielos todavía está en reparación. - I hope there is no earthquake today, because the skyscraper is still under repair.

Because after verbs expressing hope, desire or emotion—like esperar que—Spanish requires the subjunctive in the subordinate clause. Haya is the present subjunctive of haber. You’re not stating a fact (there is a tremor) or predicting it (there will be a tremor), you’re expressing a hope that it won’t happen.

Why is there no article before temblor? Wouldn’t haya un temblor be more correct?

Both are grammatically correct. Omitting un makes the statement more general (“any tremor at all”). In expressions about natural phenomena it’s common to drop the indefinite article. If you want to emphasize “one tremor,” you can say no haya un temblor, but no haya temblor is perfectly natural.

Why is it el rascacielos if it ends in -s? Doesn’t that look plural?

Rascacielos is one of those invariable nouns: singular and plural are identical. You say el rascacielos for one skyscraper and los rascacielos for more than one.

What does está en reparación mean? Can I use se está reparando instead?

Está en reparación is a passive-style expression meaning “is under repair.” Se está reparando is the pronominal (active) form, “is being repaired.” Both convey the same idea; the first emphasizes the state, the second the action.

What’s the difference between todavía and ya?

Todavía means “still,” indicating that something continues (the skyscraper remains under repair). Ya means “already,” marking that something has happened or is completed. They’re kind of opposites.

Why is porque one word with no accent? How is it different from por qué?

Porque (one word, no accent) is the conjunction “because.”
Por qué (two words, with accent) appears in questions to ask “why.”
There’s also porqué (one word, accented) as a noun meaning “the reason.”

Where does the negative no go, and why is it placed before haya?

In Spanish, the simple negation particle no always precedes the verb. So you say no haya. You can’t put no after the verb in this structure.

Do I always need the conjunction que after esperar?

If esperar introduces a subordinate clause, yes: esperar que + subjunctive. If instead you follow esperar with an infinitive, you drop que (e.g. Espero ver la película).

Could I use ojalá instead of espero que? What’s the nuance?

Yes, you can. Ojalá (often without que) also triggers the subjunctive:
“¡Ojalá no haya temblor hoy!”
Ojalá feels more exclamatory or heartfelt, while espero que is more neutral or formal.

Can todavía move around in the sentence, or does it have a fixed position?

Todavía usually sits before the main verb (todavía está), but you can also say está todavía en reparación. Just keep it close to the verb it modifies and don’t split fixed expressions like en reparación.