45 min door in 60 min wall

[rbcameron1]

I've searched the code forum for this answer, as well as google and can't find a solid answer.

Can someone explain to me why I only need a 45 minute door in a 60 minute fire separation (wall)? and yes, I've heard the "because doors only need to be rated for 3/4 of the wall" answer.

Why is it not the same as the wall assembly i.e. 60 min? Obviously fire isn't like electricity and finds the path of least resistance, but assuming a fire happened right by a door and wall, would it not technically burn through the door quicker than the wall, negating the usefulness of having a 60 min. wall?

Thanks for any solid leads to this. Its for my own knowledge.

-young architect

 

[hlfireinspector]

Door ratings are lower because no fire load is normally stored in the path of travel and the burning intensity will be lower against the door.

 

[Builder Bob]

hlfireinspector has the answer..... that is the reason why the fire codes are so strigent on storage in the means of egress.....

 

[cda]

I've searched the code forum for this answer, as well as google and can't find a solid answer.Can someone explain to me why I only need a 45 minute door in a 60 minute fire separation (wall)? and yes, I've heard the "because doors only need to be rated for 3/4 of the wall" answer.

Why is it not the same as the wall assembly i.e. 60 min? Obviously fire isn't like electricity and finds the path of least resistance, but assuming a fire happened right by a door and wall, would it not technically burn through the door quicker than the wall, negating the usefulness of having a 60 min. wall?

Thanks for any solid leads to this. Its for my own knowledge.

-young architect

But it also depends what that one hour wall is for

Sometimes it does require a 60 minute door

 

[mjesse]

Door ratings are lower because no fire load is normally stored in the path of travel and the burning intensity will be lower against the door.

This ^

But it also depends what that one hour wall is forSometimes it does require a 60 minute door

...and this ^

mj

 

[Paul Sweet]

Sometimes a 20 minute door is adequate (corridors). This is because in the 1950s & 60s corridors were typically built of block which was assumed to have a 1-hour rating, and solid-core doors, which can withstand fire for 20 minutes or so, were used in commercial construction.

A 45 minute door is usually adequate, as hlfireinspector explained.

A 60 minute door is required in exits (stairs and exit passages) for added safety.

 

[cda]

Boy did we give a """ definitive """" answer to the OP!!!!!!!!

I think he is just going to put in a two hour door and call it good.

 

[cda]

Sometimes a 20 minute door is adequate (corridors). This is because in the 1950s & 60s corridors were typically built of block which was assumed to have a 1-hour rating, and solid-core doors, which can withstand fire for 20 minutes or so, were used in commercial construction.A 45 minute door is usually adequate, as hlfireinspector explained.

A 60 minute door is required in exits (stairs and exit passages) for added safety.

and control areas?

 

[FM William Burns]

This may help in understanding the fire science behind the lower ratings as my colleague from Mississippi suggests:



NFPA 101 Commentary - The fire protection ratings of the opening protectives aresometimes permitted to be of a lower rating than the fire resistance rating ofthe fire barrier openings to be protected. For example, a 2-hour fire barrieris permitted to have its openings protected by 1½-hour fire protection–rateddoor assemblies. The perceived mismatch of ratings actually accomplishes a reasonable, practical match — as explained in the paragraphs that follow.



The test procedures on which the ratings arebased, that is, NFPA 251/ASTM E 119/ANSI/UL 263 for fire barriers and NFPA252/ANSI/UL 10B/ANSI/UL 10C (see commentary following 8.3.3.3) for fire doors,are different.



Although combustibles placed against a fireresistance–rated wall expose the wall to a considerable fire challenge, a fire protection–rated door assembly does not usually have combustibles placed against it, because the opening must be clear to use the door. Such a scenario suggests that, if a door — for example, a second door to a storage room that is no longer needed — is not to be used and combustible storage is to be placed atthe door opening, the door should be removed and the opening filled with material to restore the wall to its required fire resistance rating.



Commentary 8.3.3.3



The acceptance criteria for fire protection–rated assemblies, such as fire doors, differ from those for fire resistance–rated construction, such as a wall or floor/ ceiling assembly. The limitation of temperature rise through the fire door is not normally a measure of acceptance, although it is a measure of acceptance for a fire resistance–rated assembly such as a wall. In addition, during the course of the fire test, fire doors will expand on the exposed side and, as a result,will warp — sometimes expanding through the door opening at the top of the door. This expansion and warping can result in some flaming through the top of the door openings. The test standards recognize this phenomenon, and a certain amount of such flaming is permitted under the acceptance criteria. This does not adversely affect safety, given that fire protection–rated assemblies are intended to protect relatively small openings in larger fire resistance–rated barriers. Also, to maintain the door as usable, combustible materials are not typically stored in front of the door opening.