Questions & Answers about Er hat das Haus noch nicht gebaut.
Why is gebaut at the very end of the sentence?
In German's conversational past tense (the Perfekt), the helper verb (here, hat) takes the normal second position, but the past participle (gebaut) is always pushed all the way to the end of the sentence.
How do we make the past participle gebaut from the infinitive bauen?
Regular (or "weak") verbs form their past participle by adding ge- to the front of the verb stem and -t to the end. The stem of bauen (to build) is bau, so it becomes ge-bau-t.
Why does the German sentence use noch nicht for "not yet"?
Literally, noch means "still" and nicht means "not", making "still not". In German, this phrase (noch nicht) is the standard way to express "not yet".
Why doesn't the word das change here, since das Haus is the direct object?
You are right that das Haus is the direct object, which puts it in the accusative case. However, for neuter nouns like Haus, the word for "the" (das) looks exactly the same in the accusative case as it does in the nominative (subject) case.