I have two thoughts about this.
First, the thing to keep in mind here is that different languages use different tenses differently.
In English, for example, I'd use the present tense followed by the future tense followed by the present tense to say
If you arrive tomorrow, I'll see you.
In French, however, such a thing would make no sense. How can you use the present tense for something that's happening in the future? So I'd use two future tenses:
Si tu arriveras demain, je te verrai. ["If you'll arrive tomorrow, I'll see you." ]
In Latin, which is often even more specific when it comes to things happening in the future I'd use a future perfect followed by a future, since for me to see you you have to have arrived already.
Si crás advéneris, té vidébó. ["If you will have arrived tomorrow, I'll see you."]
The Latin arrangement of tenses is correct in English, but it's not what we'd say. The French isn't even correct—you can't say "if you'll arrive tomorrow."
The point is that different languages can have different grammatical structures to communicate the same meaning.
Second, I actually think that ædificávérit is a perfect subjunctive rather than a future perfect indicative. Perfect subjunctive followed by a perfect indicative in a conditional sentence is rare, but it's not unheard of (Harkness 511, 512). Mixed conditionals are often wonky to translate in Latin, but it's the difference between "If the Lord doesn't build the house, they who built it labored in vain" (future perfect indicative) and "If the Lord didn't build the house, they who built it labored in vain" (perfect subjunctive). To me the second makes more sense—the idea is that God has to do the building with them, not that, once they're finished building, God shows up and does the real building.
Actually, a third thing: welcome to the site!