I saw a building on the news where the scaffolding had fallen down and it looked really dangerous.
この場合、次のような言い方ができますよ。
ーI saw a building on the news where the scaffolding had fallen down and it looked really dangerous.
「足場が崩れたビルをニュースで見たけど、すごく危そうだった」
to fall down で「崩れる」と言えます。
ご参考まで!