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EDIT/NOTE: This phrase is from a legal document, so rules of plain language / literal interpretation are assumed to apply, so please refrain from assuming what you believe was intended by the writer. THIS IS NOT A LEGAL QUESTION, but one about proper grammatical logic. It would be highly appreciated if you referenced English grammar rules to support your point.

I've been debating with someone over the correct grammatical interpretation of the following sentence:

Structure must not exceed 12 feet by 12 feet base and 12 feet in height.

I am fairly convinced this means the structure must exceed both base and height dimensions in order to fail to meet the requirement. However they argue if the structure exceeds either base or height dimensions, then it will fail to meet the requirement.

• Here are the two ways this could be logically interpreted, both returning opposite results:
  
  

  
  

  H = 10, B = 20

  
  
  

  not (H > 12 and B > 12) ------> True

  
  
  

  not H > 12 and not B > 12 ------> False

  
  

  
  

I believe my interpretation is correct since there is only a single "not exceed", as well as no commas in the sentence. Whereas if the sentence said "not exceed ... and not exceed..", then that would follow the second logic:

Structure must not exceed (12 feet by 12 feet base and 12 feet in height) ------> True

Structure must (not exceed 12 feet by 12 feet base) and (not exceed 12 feet in height) ------> False

Furthermore, if the sentence used an "or" instead of "and", then that would mean that exceeding either constraint would result in failure to meet the requirement:

Structure must not exceed 12 feet by 12 feet base or 12 feet in height.

Grammatically speaking, I believe the "and" is a coordinating conjunction forming a compound object, upon which the "not exceed" is acting singularly to both objects. Is this accurate?

Welcome to ELU, and thank you for an interesting and carefully thought-out question. And you have a point. For example:-

You should not consume wine and pork.

This is troublingly ambiguous: it seems that as long as I refrain from one of them, I have fulfilled the requirement: especially if we are following the rules of formal logic, according to which A&B <--> not (A and not B) {A and B implies not (A and not B)}. Only the obvious context of Jewish and Islamic practice makes it obvious that both are forbidden. So we had better say instead:

You should refrain from wine and pork.

Now there is no possible doubt: you cannot have either. The grammar forbids it. But we have to remember that in the rules of propositional logic, 'A' and 'B' stand for propositions.

Structure must not exceed 12 feet by 12 feet base and structure must not exceed 12 feet in height. or rather: It must be the case that structure does not exceed 12 feet by 12 feet base and it must be the case that structure does not exceed 12 feet in height.

Both clauses must be true for the whole rather clumsy disambiguated sentence to be true. Negatives present a minefield of ambiguity. You have smartly prevented answerers from resorting to common sense to say that it is obvious, in the context of building permits that both height and footprint are subject to the scale limit.

You are also right to say that the conventional way round this logical ambiguity is to use the disjunction 'or' However, even this does not remove ambiguity, as 'not A or B' means 'not A implies B'. So we have to have 'neither A nor B'. In other words, to prevent any possibility of ambiguity we should have to say:

Structure must not exceed either 12 feet by 12 feet base or 12 feet in height.

I wish all writers paid the attention to univocality that you are paying. However, sadly attention to precision of meaning seems to be in decline. And grammar, as a system of classifying what people actually do must sooner or later follow usage, which is, after all the the key final word of ELU.

It is ambiguous, there is not a answer which will determine if the correct interpretation is

• must not exceed both X and Y


• must not exceed at least one of X or Y

It if comes from legal code, then the only source of truth is case law depending on your jurisdiction, or a legal judgement.