On this point, it seems to me that a "placed" bomb would sit in the middle of the floor, unless it was placed near the framing to try to ignite it. OTOH, a "thrown" bomb would possibly roll until stopped by the framing, assuming it was round.
You can almost picture the big, strong 6' 2" workman lighting the bombs and then taking off...and then calling the firemen on himself because there was a LOT of smoke.
If Jack was going to get rid of the Marini House...he'd call for a Predator.