@Brisse A tip: Add a piece of 1/2 or 3/4" wood plank or plywood that fits closely between the upper and lower shelf in the middle of every shelf from the bottom up to support/carry the loads on the shelves and under the base to the floor if the base isn't sturdy enough. Of course, this becomes a bit more complicated for wall-hung shelves that don't rest on the floor, in which case you can do the same and reinforce the bottom shelf to take the load. @Dreamnghrt