Reword the subrule “Integrity” (or create it as a subrule of The Building if it doesn’t exist) to the following:

Each Block of the Building has an Integrity score, which is an integer that is not publicly tracked but which is an emergent property of its relative position and composition in the Building, and which must be specifically recalculated whenever it is called upon in the completion of an action.
A Block’s Integrity is -1 if it is Empty.  Otherwise, it is the number of consecutive blocks directly above itself that are not _, plus the number of Supportive blocks below it.  Then, if the block is Heavy, the Integrity score is doubled.

If “That Guy Who Topples Your Tower For No Reason” passed, add the following to “Integrity”:

If the block is Weakened, the Integrity score is halved, rounding down.

If “Underlay, Underlay, A Rebar, A Rebar” did not pass, add the following to the rule Building Contents, before the table:

Each Material may have Properties, as determined by the table below.

In the same rule, add a new column to the table for Properties, and give Stone the value “Heavy, Supportive” in that column. Add the following new Material to the table:

| Rebar || R || Modern girders to support vertical construction. || Supportive