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20 min. doors R309.1

rktect 1

rktect 1

Gold Member
Joined
Oct 20, 2009
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1,112
Location
Illinois
I just want to go over this a bit. R309.1 for door from garage to residence.

The requirement is for either a 1 3/8" solid wood door, 1 3/8" solid (don't know how that is achieved-maybe they mean flat) or honeycombed core steel doors or a 20 minute fire rated door. Our village actually increased the door thickness to 1 3/4" for both and removed the reference to 20 minute fire rated doors completely.

First, who knows what the difference is in a 20 minute door and a 1 3/8" door as listed above?

Second, is a 20 minute fire rated door a B label door or different label? For some reason I thought a B label door was 45 minutes.

Third, If a B label is different from a 20 minute rated fire door, what is that difference?

I just thought I'd start a little discussion for the BB.
 
The only time I have ever encountered the "b-label" door is in association with garage doors into residential spaces. If a b-label door is a 2 hour rated door, why would anybody spec this out for this application? It appears that the door, per IRC, would be an e-label door, per your pdf above, and I have never seen that on plans. They usually list 1 3/4" solid wood or metal doors or like I said above a b-label door, which is basically way over code requirement.
 
That doesn't really tell me the difference though. A label means it has been tested, while the other is the equivilent of. Did they have to use intumescent paint, a special threshold, or other materials? I aksume that the labelling of the door becomes an actual assembly and not just the door panel itself. What label is a 20 minute fire rated door? Like I said, anytime I have seen it speced on the drawings it is called a b-label door. Is it actually an e-label as the pdf implies? It's a bit vague on that point but....
 
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The 20 minute door and the 1 3/8 metal door are the same. You pay extra for them to put a label on it!
 
Okay, so here is a new question.

Per the IRC they allowed the 20 minute fire rated door. I said that our village removed this section and changed the 1 3/8" requirement to 1 3/4" min. depth. What would the equivalent of 1 3/4" to labelling be? If someone came in and said they have a 20 minute rated door I would say not acceptable. If they said they have a b-label door, if the 2 hour rating per the pdf above is correct, I'd have to allow it as an acceptable alternative. Does anybody know what the equivelent of 1 3/4" solid wood or steel doors are?
 
Back in the early 1970s when rated corridors & 20 minute door were written into codes, 1 3/4" solid-core wood doors were typical for public buildings. Somebody figured out that a 1 3/4" solid-core wood door with the internal blocking all bonded together took about 20 minutes to burn through, so the prescriptive standard was changed to a performance standard. In most cases the only difference between a 1 3/4" solid-core wood door and a 20 minute labeled wood door is the label (and the price).

1 3/4" thick doors are more common in commercial and high-end residential construction. 1 3/8" thick doors are more common in residential construction. If a 1 3/4" solid-core wood door takes 20 minutes to burn through, a 1 3/8" thick wood door would probably burn through in a few minutes less.

The CABO code originally required a 1 3/8" solid wood door between a house and garage. The 20 minute door was added as an option once they became more readily available. They are available in different materials, such as embossed metal 20, fiberglass, or even wood panel doors of the correct species and panel thickness, in addition to plain flush doors.

B-label doors are seldom used in single family residences. They are required for 1 hour rated walls, other than corridor walls. A B-label door has a 45 minute fire rating. The door rating is allowed to be less than the wall, because debris that could catch fire is seldom (hopefully never) piled against a door. I think that door labels no longer officially have a letter rating - just the number of minutes.
 
The letter designations for rated doors are obsolete, in no small part because they were confusing.

Doors are available based on their rating in minutes.
 
Here's a quick run-down of the different labels. The letter designations are not obsolete...we still use them in the door industry.

A - 3 hours (hollow metal)

B - 90 minutes (typical) or 60 minutes (less common)

C - 45 minutes

D & E - used on exterior doors where there is a risk of fire exposure from outside the building (very rare)

20 minutes - no letter designation

With hollow metal doors and 20-minute wood doors, there's virtually no difference between the rated and non-rated versions except the label. The 45-, 60-, and 90-minute wood doors have a mineral core instead of a particleboard, structural composite lumber, or stave core that you'd have on a 20-minute wood door.
 
Doors are rated and labeled in minutes and hours. The labels A, B, C, etc. never were intended for doors. They are/were opening classifications and doors of various ratings might be used to meet the requirements of a particular opening...the letter designations might also refer to other types of opening protectives such as fire shutters.

Obviously, using letter designations in lieu of the actual nomenclature of door labels can be a source of confusion and misinterpretation.

The only letter which is appropriate to apply to a door is "S." Otherwise using letters is a poor way to communicate requirements.
 
Well, you can say that again. I don't think the architectural community has been involved in this change from understanding the letter system to min/hour rating system. I get plans all the time with B-label on them. In fact I have one today for a commercial tenant finish out which has B-label on a door. So is that a 45 min, 60 min or 90 min door, because even on this BB we seem to be a little confused about it.
 
Otherwise using letters is a poor way to communicate requirements.
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I won't take that personally. :) Right, wrong or otherwise, the door industry still uses letter designations, often in conjunction with the number of minutes/hours, but sometimes informally just the letter ("It's an A-label door."). Currently, the labels typically state the minutes/hours and sometimes the letter designation. In the Good Old Days, having the letter designation on the label was more common, and those doors will be around for a long time, so no harm in knowing what they mean, right?

Here's some more info from Annex D in NFPA 80, which states that fire doors are classified by the hourly rating, the alphabetical designation, or a combination of the two:

D.1 New and existing fire doors are classified by one of the following designation systems:

(1) Hourly rating designation

(2) Alphabetical letter designation

(3) A combination of (1) and (2)

(4) For horizontal access doors, a special listing indicating the fire-rated floor or floor–ceiling or roof–ceiling assemblies for which the door can be permitted to be used

D.2 The hourly designation indicates the duration of the fire test exposure and is known as the fire protection rating. Fire protection ratings of fire doors meeting this standard should be as determined and reported by a testing agency in accordance with NFPA 252, Standard Methods of Fire Tests of Door Assemblies. (See ASTM E 2074, Standard Test Method for Fire Tests of

Door Assemblies, Including Positive Pressure Testing of Side-Hinged and Pivoted Swinging Door Assemblies; UL 10B, Standard for Safety Fire Tests of Door Assemblies; UL 10C, Standard for Positive Pressure Fire Tests of Door Assemblies; and CAN4-S104-M80, Standard Method for Fire Test of Door Assemblies.)

D.3 The alphabetical letter designation was one method employed to classify the opening for which the fire door is considered suitable. Traditionally, the relationship between the alphabetical designation and its use was as follows:

(1) Class A—Openings in fire walls and in walls that divide a single building into fire areas

(2) Class B—Openings in enclosures of vertical communications through buildings and in 2-hour rated partitions providing horizontal fire separations

(3) Class C —Openings in walls or partitions between rooms and corridors having a fire resistance rating of 1 hour or less

(4) Class D—Openings in exterior walls subject to severe fire exposure from outside the building

(5) Class E—Openings in exterior walls subject to moderate or light fire exposure from outside the building
 
In fact I have one today for a commercial tenant finish out which has B-label on a door. So is that a 45 min, 60 min or 90 min door, because even on this BB we seem to be a little confused about it.
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A B-label is either 60 or 90 minutes (45 minutes is a C-label). B-label doors are usually 90 minutes, because the only place you would use a 60-minute door is in a shaft, exit enclosure, or exit passageway wall with a 1-hour fire rating.
 
My question then still stands.

Why do architects specify "b-label" doors from garages into residences when a "b-label" door is a door for a 2 hour wall yet code requires a 20 min fire rated door? For some reason I don't think they mean a 90 min door and as I posted earlier, I thought the b-label for this condition was a 45 min door.
 
Why do architects specify "b-label" doors from garages into residences when a "b-label" door is a door for a 2 hour wall yet code requires a 20 min fire rated door?
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I mainly work on commercial projects but I've looked into the requirements for a door between the garage and the house before. I don't know why an architect would ask for a B-label door there - probably because he/she misunderstands the requirement. I've typically seen a 20-minute door or the equivalent. Here's what our residential code says:

"5309.1 Opening Protection. Openings from a private garage directly into a room used for sleeping purposes shall not be permitted. Other openings between the garage and residence shall be equipped with solid wood doors not less than 1 3/8″ inches (35 mm) in thickness, solid or honeycomb core steel doors not less than 1 3/8″ inches (35 mm) thick, or 20-minute fire-rated doors. All such panel doors shall be labeled with a minimum 20-minute fire-resistance rating. Self-closing devices and fire-resistive-rated door frames are not required. All door openings between the garage floor and the dwelling shall be provided with a raised sill with a minimum height of four inches (102 mm)."
 
Some men with dull pencils who draw wavy lines don't know any better.

I guess I'm one of them. I just noticed that I got B & C label confused on my previous post!
 
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rktect 1 said:
Well, you can say that again. I don't think the architectural community has been involved in this change from understanding the letter system to min/hour rating system. I get plans all the time with B-label on them. In fact I have one today for a commercial tenant finish out which has B-label on a door. So is that a 45 min, 60 min or 90 min door, because even on this BB we seem to be a little confused about it.
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Since the IBC requires opening protectives to be rated in minutes, reject the plan. That's the easiest way to find out which it is.

Old habits die hard, even if they're bad ones.
 
brudgers said:
Since the IBC requires opening protectives to be rated in minutes, reject the plan. That's the easiest way to find out which it is.Old habits die hard, even if they're bad ones.
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That was the conclusion I came to as well. Ask for the rating in minutes.

Why fart around trying to figure out what A, B, C or Z is.
 
LGreene said:
A B-label is either 60 or 90 minutes (45 minutes is a C-label). B-label doors are usually 90 minutes, because the only place you would use a 60-minute door is in a shaft, exit enclosure, or exit passageway wall with a 1-hour fire rating.
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Just out of curiosity, which of the testing labs provides "b" labels for doors?

UL typically provides ratings in minutes, as does WHI.

In my opinion, these days it would be odd for one to label a door using an opening designation.
 
LGreene said:
I mainly work on commercial projects but I've looked into the requirements for a door between the garage and the house before. I don't know why an architect would ask for a B-label door there - probably because he/she misunderstands the requirement. I've typically seen a 20-minute door or the equivalent. Here's what our residential code says:"5309.1 Opening Protection. Openings from a private garage directly into a room used for sleeping purposes shall not be permitted. Other openings between the garage and residence shall be equipped with solid wood doors not less than 1 3/8″ inches (35 mm) in thickness, solid or honeycomb core steel doors not less than 1 3/8″ inches (35 mm) thick, or 20-minute fire-rated doors. All such panel doors shall be labeled with a minimum 20-minute fire-resistance rating. Self-closing devices and fire-resistive-rated door frames are not required. All door openings between the garage floor and the dwelling shall be provided with a raised sill with a minimum height of four inches (102 mm)."
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Hi Folks,

LGreen's quoted code section is very clear. In that it states that it's the door that needs the rating and not the frame

I'd like to hear what others here think about section R302.5.1(2009 ICC).

It's my interpretation that as long as the door is:

1) solid wood with a minimum thickness of 1 3/8"

2) solid or honey comb core steel same thickness requirement

3) 20 minute fire rated door

Any of these can be mounted in any door frame rated or not.

What say You?

Thanks

Bill
 
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