When is a fire rated cabinet required in a fire rated wall?
When it penetrates one of the membranes of the fire-resistance-rated wall, such as recessed or semi-recessed cabinets. A surface-mounted cabinet on a fire-resistance-rated assembly need not have a fire-resistance rating.
I have a situation where the Contractor has purchased standard Fire Extinguisher Cabinet boxes and is looking for some suggestions on how he can install them in the fire rated wall. The boxes are to be semi-recessed?
Either have him/her replace the boxes or have him/her wrap the Type X GWB into the recess so that the top, bottom and all sides are covered with GWB.
To maintain the wall rating you need a rated box. Merely wrapping the box with rated gypsum board doesn’t give you a rated cabinet, although for years many local jurisdictions around here accepted that method.
Okay, before you proceed any further, let’s identify all the details:
Is the wall to be of fire-resistive construction per the Construction Type, or is this a fire-resistance-rated assembly, such as a fire barrier, fire partition, or fire wall?
What is the required hourly rating for the fire-resistive construction or fire-resistance-rated assembly?
Three Options:
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Frame the rough-in opening oversized to accommodate a complete wrapping of the recess in “Type X” gypsum board. Either have each condition (head, jamb, sill) match an acceptable rated assembly tested by UL or similar, or have your Fire Marshall approve any deviations before starting.
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Substitute similar fire rated enclosures. Does your specification tell them to provide rated enclosures for rated locations?
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Shift fire extinguisher locations onto unrated walls or furred-out walls away from the rated wall line while maintaining your required spacing. We try to find a useless space adjacent to a column and a wall to place the enclosures in a bit of non-rated wall.
Which ever costs less in time and money is the ball to carry.