Your building blocks are known as the atoms in the Boolean algebra or field of sets generated by the $A_i$. Each building block will consist of points that have all the same pattern of answers for membership in the various $A_i$. To see this, observe first that by maximality any building block will respect this equivalence and therefore be a union of such atoms. Conversely, if a set has points with two different patterns of answers, then it will contain points from two $A_i$ without being contained in their intersection. (Specifically, if $x,y\in B$ and $x\in A_i$ but $y\notin A_i$, then pick $j$ such that $y\in A_j$, and observe that $B$ meets both $A_i$ and $A_j$, buit is not contained in $A_i\cap A_j$.) So the building blocks are the atoms.
If your family is finite as you indicated, then the Boolean algebra generated by the $A_i$ consists precisely of the unions of blocks. This is the representation theorem showing that every finite Boolean algebra is isomorphic to a finite power set---the power set of the atoms.
In the infinite case, should you entertain infinitely manyhowever, the Boolean algebra generated by the $A_i$ may be atomless---it may have no atoms at all, then unfortunatelyand this is a fascinating case. Nevertheless, you don't getyour blocks still form a partition, for thereand are atomless Boolean algebras. Neverthelessprecisely the atoms in the infinitary-generated field of sets, these Boolean algebras are fascinatingstill determined by my argument above by the patttern-of-answers to membership in the $A_i$.