The roof is structurally unsound.

这屋顶结构不牢固。

《牛津词典》

The church was structurally unsound.

这座教堂的结构不安全。

《柯林斯英汉双解大词典》

The house roof was (structurally) unsound.

这屋顶(结构)不牢固。

youdao

It would be like deciding to add another floor to a house that is known to be structurally unsound.

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Those services include getting to bodies in attics or other hard-to-reach places or in buildings that may be structurally unsound.

MSN: Authorities end search for bodies in La. - US news - Katrina, The Long Road Back | NBC News

They chose not to give us this school, to put us in a school that they're now saying is structurally unsound.

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