A drop case for building

The utility model relates to a drop case for building, including a plurality of drop case units that from top to bottom connect gradually, drop case unit all includes: first box unit, second box unit, first box unit and the unit connection of second box constitute vertical column drainage chamber, the buffering swash plate, the buffering swash plate is fixed in first box unit, and the buffering swash plate is 3-45 degrees with the contained angle of horizontal plane, connect according to following mode between a plurality of drop case units: the first box unit of upper portion drop case unit is with the second box unit connection of lower part drop case unit adjacent with it, and the second box unit of upper portion drop case unit is with the first box unit connection of lower part drop case unit adjacent with it, the base, the base has the wash port to base and drop case unit fixed connection bottom. The invention is created the drop case and can be descended the in-process at rivers and reduce the potential energy of water, and then reduces the water velocity, avoids the destruction of water impact to the drop bottom of the case building element of portion