Answer: Unsafe
This method of stacking is unsafe. The safe way to store materials is by stacking them in tiers that should be stacked, racked, blocked and interlocked to secure them properly, avoiding falling, sliding or worse, to collapse.
Moreover, the passageways should be keep clear to give free and safe movement of materials or to the workers around the area. However, not all materials can be stacked, it will depend on its shape, size or the fragility of the materials. With this case, they can be safely stored in bins or shelves.