Along with the ancestral past shared by Randy Bragg and the house ("shared" metaphorically by the house), they also share a present and a future, and there is a dual aspect to the present and future states they share. In the present, both are in states of "disrepair," with Randy not remembering, "exactly," when he "started taking a drink or two before breakfast," and with the house showing its "ungainly and monolithic" side more than its Victorian, bay-windowed elegant side. In the future, it is the inner character--and the structural character--of the man and the house that will be most importantly symbolized by the Cold War era present-day Bragg House.
While man and house may have fallen into disreputable conditions in the present, it is the deeply embedded strength in the Bragg character that the house will most importantly symbolize in the very near future. The house, though presently seen as ungainly by the standards of the Cold War era, is "tall" "monolithic" "broad." When Mark's foretold "Alas, Babylon" comes about (a day after his foretelling) and the civilized world comes crashing down in a blaze of brimstone, the strength that is in Randy Bragg--and in the house (both structurally and symbolically)--is enlarged and looms in the foreground of catastrophe as he shelters, provides water for, feeds and protects friends, loved ones, his "wards" and neighbors: In the strength and nobility symbolized by the Victorian house, Randy ushers in a new civilized community with its bastion the old, worn out "monolithic" house that now is the shelter that Randy offers [bastion: something that protects that which is in danger].
Food for thought: The symbolism can be carried further and applied to the Victorian--and even more ancient--values the Bragg family and the Bragg family house represent with a discussion of the place of those values in the "present day" (whether Bragg's present day or our present day) and in "the future" after the occurrence of whatever catastrophe overtakes humanity from whatever quarter and in whatever form: Will those dilapidated, monolithic "Victorian" values be the stay and stanchion that saves and shelters us, restoring order and civilization, as they saved and sheltered Randy Bragg and his fledgling community as these nestled under the wing of the Victorian house with its "broad brick chimneys" [stanchion: a strong upright supporting brace]?