Construction Type & Allowable Area

Introduction:

When figuring out a building location and size, the occupancy group of the structure, along with its construction type go hand in hand.

Combustible: Able to catch fire and burn easily, either as a flame or glow. Combustible materials are dangerous during a fire in a building.

Non-Combustible: Not flammable. It will not ignite, burn, or release flammable vapors when exposed to heat/fire.

Non-combustible does not necessarily mean that the material is fire-resistant, although most non-combustible materials typically have very high fire resistance.
An example of a non-combustible material with okay fire-resistance is steel. Steel loses its strength quickly in fire, and will distort/collapse/deform, but it will not burn, ignite, or release flammable vapors. Steel keeps its structural integrity until about 600॰F, and retains about 50% of its strength at 1100॰F. A house fire burns at temperatures typically over 1000॰F, and can reach 1500॰F. It is for this reason that steel needs to be ‘fireproofed’.

In the IBC, each building is classified as belonging to one of five major types of construction.

TYPE I (1): Are the most fire resistive
TYPE I (1) & II (2) : Non Combustible
TYPE III (3), IV (4), V (5): Combustible
- TYPE V (5) : Is the least fire resistive (the most at-risk)