Dealer Portal Blog

October 14, 2020

Rack Design: The Importance of Flue Space

flue space helps fire spread upward

There’s a surprising amount of math and measuring involved in something seemingly so simple as pallet rack design. One thing to always remember: incorporate flue space. Flue space is the space between rows of pallet rack or between a row and a wall.

Read on to find out why it’s important and how to include it in your designs for the best results.

Why Leave Room?pallet overhang

Warehouse space is valuable so it seems like nonsense to leave all that room between rows of rack. So why do it?

First, remember that rack is designed so that the beams support most of the weight of the loads, even if you’re using pallet supports or decking. As a result, some of the load must extend past the front and back of the rack system. 42″ deep rack is popular because the most common pallet depth is 48″, allowing for 3″ of overhang both front and back, as shown in the picture to the right.

As a result we already need 6″ of room between back-to-back rows of rack, but there are several good reasons that the design standard for back-to-back rows doubles that number:

  • First and most obvious, to prevent pallets and loads from colliding with pallets and loads in the adjacent row.
  • To avoid fines from the Fire Marshal. There must be room between the rows for the water from sprinklers to reach the floor.
  • Flue space also helps a fire spread upward, bringing it closer to the ceiling-mounted sprinklers.
  • To have a place to hide building columns. No one wants a column in a bay, eliminating pallet positions.

Leaving room for rows of rack that are next to a wall is important, as well. This prevents load damage and damage to pipes, conduits and other fixtures that may be mounted on the wall. This is especially important in cooler applications where the walls consist of thin metal and styrofoam and are very easily damaged. In fact, we strongly recommend pallet stops for those applications.

More on Row SpacingROW SPACER

When row spacers and wall ties are needed:

  • With back-to-back rack systems. Row spacers and wall ties add strength and stability to these systems.
  • Only necessary when the frame height exceeds 6 times the depth. In other words, row spacers and/or wall ties are needed for a 42″ deep frame that exceeds 21 feet in height.
  • When they are used, one should be installed for every 10 feet of height.

We stock Interlake, Ridg-U-Rak and Mecalux row spacers.

If you want to learn more about rack system design, remember that we’ve placed a lot of information on our How-To page.  If it doesn’t have what you need or you want more information just get in touch. We’re here to help you succeed.



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