Ok, let's break this down.
Taking away "extra" parts of the sentence that don't affect the verb tense:
...there is more than one Building....
Building is what is used to determine the verb tense. Since building is singular, use 'is'.
For the second example:
In a scenario where there are more than five children at a Location, that Location should still only be counted once.
Taking away...
...there are more than five children....
Here the word children determines the verb tense. The word children is plural, so 'are' is used.
Rewording the sentences can make it a bit clearer, for purposes of this discussion:
There
is one building at a location.
There
are five children at a location.
I used to rock and roll every night and party every day. Then it was every other day. Now I'm lucky if I can find 30 minutes a week in which to get funky. - Homer Simpson
Arrrr, mateys! Ye needs ta be preparin' yerselves fer
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