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Do You Know Your Construction Classes? Construction Class 4: Masonry Non-Combustible

August 5, 2013

As with all other construction classes, Construction Class 4 (CC 4) can be difficult to identify if the wall and roof assemblies are obstructed.  This has been mentioned a couple of times in previous articles and is, again, where a Field Rep’s experience and training becomes invaluable.  If you’re prospecting a new client and want to have an idea what type of structure their business is in, there are a few tricks to seeing what’s underneath all that drywall.  While a WSRB inspection will provide the most accurate information about the structure, there are a few starting places to give you an idea:

–          Many service stairwells and closets are not completely finished.  The public was not intended to see these, so sometimes they give a great view of the construction, especially near the ceiling.

–          In restaurants and retail occupants, the behind-the-scenes areas tend to have fewer finishing touches. In kitchens and stockrooms, you can generally get a good view of the wall construction and the ceiling assemblies.

–          In sprinklered buildings, the riser room commonly gives the best view of the wall and roof construction, and how the two meet.

“Buildings where the exterior walls are constructed of masonry materials, as described in [Rule 15.B.2, Joisted Masonry], with the floors and roof of metal or other non-combustible materials.”

Exterior Walls or Exterior Structural Frame:

–          Any type or thickness of load-bearing masonry

As with Construction Class 2, CC 4 buildings have walls that are of any load-bearing masonry construction, including tilt-up concrete, concrete, hollow concrete block, hollow tile, etc.  From this aspect alone, the two buildings are virtually indistinguishable:

construction class 2 building

Construction Class 2 – Joisted Masonry

Construction class 4 - masonry non-combustible

Construction Class 4 – Masonry Non-Combustible

How is CC 4 different from a CC 2-Joisted Masonry building?

Floors and Roof:

–          Metal or masonry, floor or roof decks supported by metal frame (rated as noncombustible)

–          Floor or roof assemblies with a fire-resistive rating less than R.1 hour

Construction Class 4

In the above picture, the wall is made of a tilt-up concrete, and along the top you can see the metal tube trusses being supported by metal posts and the exterior walls.  The metal in this building does not have any fireproofing on it, so it will collapse faster in a fire than a thicker, protected metal or steel.  While the materials in CC 4 don’t burn as easily as wood, they do fail structurally at high temperatures, like in a fire.

Next week, we’ll visit Construction Class 5, Modified Fire Resistive.

Article by: Kristen Skinner

One Comment leave one →
  1. Richard Law permalink
    August 5, 2013 9:59 pm

    Reblogged this on SOFI Blog.

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