Although we are using barrel racks for storage of some barrels, the majority of our whisky barrels (200 litres each) are stored on their side, stacked with 2x4's between rows. As we are getting tight on space, we want to know how high we can safely go. In other words, what is the maximum load on a barrel?
The Low Profile Rack has a 4” forklift opening. It is one of our recommendations for stacking six barrels high, because the stack has a lower center of gravity. All you sacrifice is the ability to get your head between the barrels in a stack. The wine can still be worked in place
This manufacturer implies that you can stack wine barrels 6 high..
If you do a Google image search for "stackable wine barrel racks" you can see lots of stacks that are six high and many that are more than that..
I think I would stack 6, and then start contacting rack manufacturers for more details if I wanted to go higher..