In the following sentence:
"Wall and roof thickness are always considered when repairing a chimney."
The sentence refers to the thickness of both the wall and the roof. Is the sentence above correct (i.e., even though "thickness" is singular and "are" is plural") or should the non-count noun "thickness" be repeated to match the plural verb "are"?
i.e., "Wall thickness and roof thickness are always considered when repairing a chimney."
Is there a rule regarding constructions like these? Hopefully, someone can help. Thanks!