The sentence
Except the buildings built towards the end of his life, the buildings
erected in Istanbul can be assumed to be his.
was recently used in a question here.
I edited to replace 'except' with the compound preposition 'except for'. I'm very unhappy with the original, but don't like to assume my gut reactions are necessarily correct.
CDO gives:
Except or except for? from English Grammar Today
We often use except and except for as prepositions to mean ‘not
including’ or ‘excluding’. They are followed by a noun or noun phrase
or a wh-clause. Both except and except for are correct after a
noun:I like all fruit except (for) oranges. (excluding oranges)
Except for Louisa, who’s away in Berlin this weekend, we’ll all be at
the party.She likes going to most sports events, except cricket matches.
This shows the choice of 'Except for' to start a sentence-initial prepositional phrase, but does not go so far as to state that the choice of the simple preposition is incorrect.
The nearest (but really reversed) question I can find on ELU is essentially
Is "Are there any vegetables except for asparagus?" correct?
to which Peter Shor provides the tantalysing answer (with which I largely agree):
I think what's wrong is the "for". [I'd say 'very iffy' in all but some unusual contexts]
Are there any vegetables except asparagus?
The grammar of when to use "except for" and when to use "except" is
governed by [a] quite complex set of rules (often, you can use either).
There probably is a correct and complete description of how this works
somewhere on the internet, but I haven't found it, so I can't tell you
why you should use "except" here; but it just feels right.
Can authorities be found giving this correct and complete description of the complex set of rules governing when to use "except for" and when to use "except" , on the internet or elsewhere?
Best Answer
I'm not an authority but anyway here is my answer. Firstly I want to point out that the occurrence of the collocation "except for" actually splits into two cases.
In one case it is a single lexical unit that is a preposition, hence accepting only noun phrases or equivalents as its 'object':
In the other case the "for" actually belongs to a prepositional phrase, and it follows the usage of "except" such as in:
Here it parses as "similar except { for { { books } instead of { video } } }". Here "except for books instead of video" adverbially modifies "similar". Likewise:
The type of phrase Y that can be modified by an "except X" phrase has to be of the same type as X, except when X is an adverbial phrase and Y can be modified by X directly. Here are more actual examples with the "except" clause fronted:
There is also a specific usage with the subjunctive that seems less frequent now:
I may have missed some details but I believe this kind of explanation is an adequate one for the major similarities and differences between "except" and "except for". For example it explains why we can say the first but not the second in each of the following examples:
So finally my answer to the original question is that both are valid English and mean exactly the same thing, although it might be better to delete redundancy:
I grant that examples of sentence-initial "except" with noun phrases are rare, but since "except" with non-noun phrases aren't avoided at the beginning of proper sentences, I think the rarity for noun phrases is perhaps due to the fact that sentence-initial "except" is frequently used to join whole sentences. If that is so, then it may be that "except for" is used for noun phrases simply because it makes it easier to process. I myself would probably have chosen to use "except for", but I did not find the other one odd.