Questions & Answers about Das Haus ist alt. Es ist nicht neu.
Why is nicht placed right before neu?
When you use nicht to negate an adjective that comes after the verb (like neu here), nicht goes directly in front of that adjective. It translates perfectly to "not new" in English.
Why does the second sentence start with Es?
Es is the pronoun for neuter nouns. Since Haus is a neuter noun (which we know because it uses the article das), we use es to say "it". If the noun were masculine (der), we would use er, and for feminine (die), we would use sie.
Why don't the adjectives alt and neu have any special endings?
In German, when an adjective is used after the verb to describe a noun, it stays in its basic dictionary form. You only add extra letters to the end of an adjective when it comes directly in front of a noun (like saying "a new house").