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The Basics on Construction Classes – Part Three, Non-Combustible

Posted by Robert Lacy on August 29, 2017

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Our six-part Basics on Construction Classifications series has reached the halfway point. This one focuses on Construction Class 3 (CC 3), the non-combustible construction type.

These articles are designed to help you gain a better understanding of the various classes so you gain more value from WSRB commercial property reports and the calculation of tentative loss costs. This series, like the classes themselves, moves from the least fire-resistive class (CC1) to the most (CC6).


The Commercial Lines Manual defines the Non-Combustible construction class as:

“Buildings where the exterior walls, floors, and roof are constructed of, and supported by metal, asbestos, gypsum, or other non-combustible materials.”  Commercial Lines Manual, Rule 15.B.3

Where you write your business will determine how often you will encounter CC 3. It’s common in warehouse districts and rural areas.

Construction Class 3 encompasses metal buildings where the structure doesn’t add fuel to the fire. A drawback to this construction class: the structural steel used is unprotected, causing it to potentially become structurally unsound or even collapse at high temperatures. You may be wondering why these buildings would be constructed. It’s because they are inexpensive to design and fairly quick to build. Warehouses and manufacturing facilities are classic examples of the CC 3 type. Many are protected by automatic fire sprinkler systems, which decreases the likelihood of the metal reaching a temperature at which the structure is compromised.



The Importance of Automated Sprinkler Systems


CC 3 exterior walls exhibit the following elements:

  • Structural, horizontal and vertical load-bearing unprotected metal supports (rated as non-combustible)
  • Metal or masonry, panels or curtain walls supported by a metal frame (rated as non-combustible)


A CC 3 building typically features a metal roof and siding. As long as you can see the horizontal and vertical load-bearing supports, this construction type is fairly easy to identify.

The below exterior image is a classic example of a CC 3 building.

 CC 3 exterior.jpg


The interior floors and roof of a CC 3 building feature:

  • Metal or masonry floors or roof decks supported by a metal frame (rated as non-combustible)
  • Floor and roof assemblies with a fire-resistive rating less than R.1 hour, The “one-hour” fire rating is given to materials able to resist standard fire exposure for, you guessed it, one hour.

The below image exhibits a standard CC 3 interior.


CC 3 interior.jpg


A few notes to help you in distinguishing CC 3:

  • Quite often, the unprotected metal looks like bare steel. It may or may not be painted.
  • Buildings are generally one to two stories tall.

Two common issues that can move a CC 3 building to a combustible classification:

  • Exposed insulation on the walls if the insulation states that it must be covered.
  • Plywood sheathing attached to the inside of the exterior walls. Since plywood is combustible, this may cause the building to fall into a combustible construction class.


What’s the best way to ensure your risk has the correct classification? Let WRSB inspect it. Commercial inspections are included in the price of your subscription. Easily request an inspection on the member portion of the website. WSRB also offers customized inspection services. Let us know your needs.


Read the next post in our series, where we cover Construction Class 4, Masonry Non-Combustible.


Robert Lacy, WSRB's Vice President, Inspection Services & Professional Development, oversees our team of commercial property analysts as they produce advisory loss costs, commercial property reports and evaluate automatic fire sprinkler systems. He is involved in the annual evaluation of our loss cost levels and ensuring we are current on coding and rating issues for commercial property. He also works to encourage continual professional development for all WSRB employees.

Topics: Building Construction, Construction Classes