Horizontal vs. Vertical Distance Away from ESFR?

9/22/2025

What does “horizontally away from the sprinkler” mean?

I recently read a technical note regarding the ESFR obstruction rule. The example question was: *“In an existing building, a 6-inch-wide steel brace runs diagonally from column to column, forming an ‘X’ between four columns. The brace is located a minimum of 48 inches below the ESFR sprinkler deflectors. Should this brace be considered an obstruction to the sprinkler discharge pattern?”*

The answer stated that the X-shaped braces are not considered an obstruction because they are located at least 1 ft away horizontally from the sprinkler (referencing NFPA 13, 2016 edition, 8.12.5.3(3)).

My confusion is this: if something is located below the sprinkler, I would describe it as being vertically away, not horizontally away.

Did I interpret the code incorrectly?

Can someone clarify the difference between “vertically from the sprinkler” and “horizontally away from the sprinkler?"

Thanks in advance.

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7 Comments

Dan Wilder

9/22/2025 07:00:55 am

Think of it as the X and Y axis within a vertical plane. The X in this case has the origin of the sprinkler and any left or right distance is the Horizontal offset, the Y being the Vertical offset.

The axis has no “negative” horizontal (X) distances, and anything above the sprinkler is not counted anyway.

The plane itself is just a slice of the cylinder with a center being the top of the cylinder (the sprinkler) and it extends down to the floor. Anything witching this cylinder may be considered an obstruction depending on the width vs horizontal and/or vertical distance.

Randy Rathert

9/22/2025 10:23:08 am

I'm confused - Where did the cylinder come into play- is this the spray from the sprinkler?

9/22/2025 01:12:49 pm

Sorry, I draw cylinders when BIM coordinating and yes, the spray cone from the sprinkler is what I am referencing.

Page 34/35 or Figure 28 was my visual thought from the below FPRF report.

https://nfpa.access.preservica.com/uncategorized/IO_104225f5-1f8a-43ef-b299-9be68f9b3091/

Jose R Figueroa

9/22/2025 01:58:58 pm

Thank you for this. I managed to download the full 160-page FPRF report to Adobe Acrobat. I saw the diagram you were referring to.

I learned something new today!

Anthony

9/22/2025 07:12:51 am

Yes horizontal is plan view. I think the reviewer just gave 1/2 the answer. (even review folks make mistakes)

9/22/2025 10:34:11 am

I'm also feeling confused. After reviewing NFPA 13 (2016), I gathered that “vertically from the sprinkler” means the straight-down distance from the deflector (e.g., 48 inches). “Horizontally away from the sprinkler” refers to the lateral offset measured from the sprinkler’s centerline to the nearest edge of an obstruction, indicating the sideways distance rather than directly below. Hope this clarifies things!

Pete H

9/22/2025 12:26:53 pm

Vertical is "up/down" away from the sprinkler. Along the plane of "height".

Horizontal is distance regardless of elevation, along the plane of "length" or "width".

If in the industry: Think about how horizontal sidewall sprinklers are orientated vs how vertical sidewall sprinklers are orientated.

If not in the industry: If you find an old tv and touch the "V-hold" dial, that stood for "Vertical Hold" and when you messed with it, the footage went Up and Down a lot.

Horizontal vs. Vertical Distance Away from ESFR?

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