Obstructed Construction: Panel Construction

MeyerFire University | FX108.51D

By Joe Meyer, PE

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FX153 SERIES

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• Notes Page [PDF]

FX153 SERIES

1. Introduction to Obstructed Construction
2. Difference Between Obstructed & Unobstructed Construction?
3. Why Does Obstructed & Unobstructed Matter?
4. Examples of Obstructed Construction: Beam and Girder
5. Examples of Obstructed Construction: Concrete Tees
6. Examples of Obstructed Construction: Composite Wood Joists
7. Examples of Obstructed Construction: Panel Construction
8. Examples of Obstructed Construction: Semi-Mill Construction
9. Examples of Obstructed Construction: Wood Joist Construction
10. Examples of Obstructed Construction: Bar Joists with Fireproofing
11. Examples of Obstructed Construction: Steel Purlin Construction
12. Examples of Obstructed Construction: Truss Construction
13. Examples of Obstructed Construction: Bar Joists
14. A Quick Recap of Obstructed Construction

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TRANSCRIPT

Obstructed Construction: Panel Construction 

So, we're continuing in our series of “obstructed construction” as a term that comes from NFPA 13 and today we're covering our example of panel construction.

…so first by the definition what are the rules that allow us to qualify a type of ceiling or roof as panel construction? 

#1. The first is a maximum area of 300 sqft or the 28 square meters. This is a two-dimensional maximum area of what that pocket size is allowed to be. Now this seems pretty straightforward and it's going to be relatively easy for us to determine. We can measure that on a plan just 300 square feet / 28 square meters maximum.  

#2. There can be no unfilled penetrations of the structural members at the edges of this pocket. So basically, on that pocket perimeter, we can't have any unfilled gaps above the structure where smoke can go. 

We can't allow that smoke to flow above girders, we can't have gaps at the roof. The definition is tactfully saying that the ribbed sheet metal roof decking can't just rest on top of structure where smoke could go right above a beam and keep on moving. In order to qualify for panel construction, there can be no unfilled penetrations along the boundary of this pocket.

Our last rule, number three. Well, part of it is more of an allowance than it is a rule, but it's that the beams can be spaced more than seven and a half feet apart and still qualify as panel construction. However, those beams have to be framed into girders and the 300 square foot or that 28 square meter area limitation still applies.

So, few questions here. In the definition of obstructed construction, we hear that beams are spaced 3 to 7-1/2 feet apart, but here under panel construction, as an example of obstructed construction back in the annex, we're now saying we're allowed to have beams spaced more than 7-1/2 feet apart. Can we still be panel construction if the beams are spaced more than 7-1/2 feet apart? 

That answer is yes because the annex material specifically saying that beams can be spaced more than 7-½ feet apart as long as that 300 square foot limitation is met and there's no unfilled penetrations along the boundary of that pocket. 

We also see this in the definition of unobstructed construction where beam members are more than 7-1/2 feet apart are typically considered unobstructed construction except for when we qualify as panel construction. That’s the case here.

Another question - does a concrete floor with corrugated steel on the bottom really need to be filled in? 

Well, in order to qualify for panel construction, yes it does. It has to be filled with a non-combustible material. An informal interpretation from the National Fire Sprinkler Association back in 2018 addressed just that. It doesn't need to be firestopped, but it does need to be filled so that smoke will not pass through those open flutes. 

Do I have to meet panel construction in order to be obstructed construction? No. Panel construction is just one example. It's one of the types that the NFPA 13 committee gives us as an example of obstructed construction. If we qualify for one of the other examples like beam and girder construction, then we wouldn't have to be concerned about those unfilled penetrations. But one way or another, if we're gonna be considered obstructed construction, we need to meet one of these types of obstructed construction.

Why do we even want to be considered obstructed construction? Again, this gives us better flexibility and allowances to locate sprinklers further down from a roof or ceiling, and potentially avoid having to have many sprinklers or avoid having to have sprinklers in every little beam pocket.

I’m Joe Meyer, this is MeyerFire University.