Wood ledger at fire rated wall

[khsmith55]

Need some help in refreshing my memory. Using a 1 hour rated fire barrier of 2x6@16" with 5/8" type X gypsum board each side. I would like to use a 2x ledger attached to the studs and “die” the gypsum board into the ledger and fire caulk the joint, to hang floor joists off of wall. Years ago (more than I would like to count) I was told a 2x flat(i.e. ledger) has higher degree of fire resistance than 5/8" type X gypsum board, have I been working under an old wives tale using this detail for over 30 years. Can someone direct me to some documentation, testing or reference for this assumption, or am I full of “whooey”. Thanks in advance.

 

[brudgers]

I don't see how that maintains fire resistance.

 

[steveray]

I'd call shennanagins on that....I am no fire guy but I believe that a 2X has about a 20min burn through.....

 

[Yankee]

The wood will combust and fail before the gyp will

 

[Frank]

Reference 2009 IBC 721.6.2

In that a 15/32 inch wood structural panel gives 10 minutes 1.5 inches of wood in the 2x would give 32 minutes which is a bit short of the 40 credited to 5//x type x gyp board. The wood framing gives the other 20 minutes.

However is the ledger exposed to the room or concealed in a floor ceiling assembly?

If the ledger is concealed it would likely last as long as the exposed 5/8 type x gyp board--3/8 regular gyp board gives 10 minutes.

What is the purpose of the wall?

 

[brudgers]

I'd call shennanagins on that....I am no fire guy but I believe that a 2X has about a 20min burn through.....

I call numerical illiteracy on that...20 minutes is not an hour.

 

[steveray]

I call numerical illiteracy on that...20 minutes is not an hour.

Correct.....your point is?....your not calling that on me? Correct? I was not saying it was even remotely compliant, hence the shennanagins...

 

[Big Mac]

The wood leger would interrupt the required one-hour rating, essentially creating an opening. To the best of my knowledge a 1.5" wood ledger does not comprise a tested or prescriptive solution to a penetration in a one-hour fire-rated wall opening.

 

[kilitact]

Need some help in refreshing my memory. Using a 1 hour rated fire barrier of 2x6@16" with 5/8" type X gypsum board each side. I would like to use a 2x ledger attached to the studs and “die” the gypsum board into the ledger and fire caulk the joint, to hang floor joists off of wall. Years ago (more than I would like to count) I was told a 2x flat(i.e. ledger) has higher degree of fire resistance than 5/8" type X gypsum board, have I been working under an old wives tale using this detail for over 30 years. Can someone direct me to some documentation, testing or reference for this assumption, or am I full of “whooey”. Thanks in advance.

Go to Chapter 7 of the IBC, section 720+, might have something,. If designed correctly could work. Some of us old guys have old wives that still work good.

 

[Builder Bob]

khsmith55 - A part of that may be true- however, in accordance with NDS the correct char rate of southern pine is about 1 1/4inch per hour. The question that I would poise to you, can you provide structural calculations to indicate the structural integrity will be maintained for the required time period required due to the erosion of the structural integrity of the wooden member due to fire exposure?