Beam Rule Apply to Wide or Wall-Obstructions?

5/14/2020

Hello all, two questions:

1) Can the rules of a beam obstruction also be used for a 4 ft (1.2 m) obstruction? Or does section 8.5.5.3.1 prohibit that arrangement?

8.5.5.3.1* Sprinklers shall be installed under fixed obstructions over 4 ft (1.2 m) in width.

2) Can the rules of a beam obstruction also be used for a 30 in (750 mm) against wall obstruction? The standard says sprinklers "8.6.5.1.2*... shall be arranged to comply with one of the following arrangements"

Or does an obstruction against a wall have to comply with Figure 8.6.5.1.2(b) and then has to have a sprinkler underneath?

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3 Comments

Mike

5/14/2020 10:09:08 am

Not sure I understand what you mean.

Is the beam located near the wall creating a pocket between the wall and the beam? Is the beam less than or greater than 30“ from the wall?

Jonathan Joseph

5/14/2020 10:34:36 am

8.6.5.1.2 Standard Spray Table. 2016ed

If the obstruction is more than 30 in. use the table.

For obstructions over 4 feet it needs a sprinkler however the question is it obstructed or not?

Use the table and see if it is obstructed and look at your designed coverage area to have coverage to the wall or adjacent sprinkler.

A residential sprinkler faces tougher obstruction guidelines.

Anon

5/14/2020 11:36:51 am

Forgive me if I am interpreting your question incorrectly, but is this like a soffit against a wall?
It is my belief (and I have seen an informal interpretation regarding this) that one isn't 'required' to place a sprinkler below an obstruction merely because it is over 4-ft. wide, if you are able to protect the floor area beneath it utilizing the "beam rule"
For the up-to 30" wide soffit, you have options including the Fig. 8.6.5.1.2(b) for up to and including 30" wide, or again the "beam rule" if you can make it work, or if it is over 30" wide.
If it is like a "shelf" more than 18" below the deflector, that is more like you are talking about, sprinklers under fixed obstructions over 4-ft. wide 8.6.5.3.3 (and Fig. A8.6.5.1.2)
(2016 Ed.)

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