How to Determine a Building's Construction Type
How building class is determined: All buildings must be classified into one of six construction classes (see number 3)., What to ask: To determine the ISO class of the building, we must therefore know the following composition of the building...
Step-by-Step Guide
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Step 1: How building class is determined: All buildings must be classified into one of six construction classes (see number 3).
Classification of a building class is based on two factors: building elements and fire-resistance rating.
These factors may not be included in the submission/documentation, in which case additional information will need to be requested.
Building elements:
The building materials used in the construction of the following elements are the foundation for classification, be they wood, steel, or masonry.
Structural frame Exterior bearing walls Interior bearing walls Exterior nonbearing walls and partitions Interior non-bearing walls and partitions Floor construction, including supporting beams and joists Roof construction, including supporting beams and joists, are comprised of Fire-resistance rating:
This is the other factor in determining construction class.
The building materials used in the construction of the building elements above will have a fire-resistance rating.
Fire-resistance rating typically means the duration for which a passive fire protection system can withstand a standard fire resistance test.
This can be quantified simply as a measure of time (ex. 0 hours, 1 hour, or 2 hours), or it may entail a host of other criteria involving other evidence of functionality or fitness for purpose. “Minimum” rule:
It is important to remember when selecting the construction class that the building is only as strong as its weakest element.
For example, a masonry building may have an unprotected wood roof.
The wood roof is the weakest member such that it has no fire-resistance.
Thus, the construction class would be Joisted Masonry (see below).
Now imagine this same building with a metal deck roof.
So long as the supporting members of the building do not contain wood then this building would be Masonry Noncombustible (see below). -
Step 2: What to ask: To determine the ISO class of the building
,, ISO is traditionally what insurance companies use to denote type, whereas IBC is what architects and builders use.
While one company may use ISO classifications, many submission documents may reference IBC classifications and it is important to be able to convert this to an ISO classification. (There have been situations where a frame building has been incorrectly classified as fire resistive because the submittal was read incorrectly!) The following explains what is expected under both:
International Building Code (IBC):
This is a model building code developed by the International Code Council (ICC).
It has been adopted throughout most of the United States.
A large portion of the International Building Code deals with fire prevention.
It differs from the related International Fire Code in that the IBC handles fire prevention in regards to construction and design and the fire code handles fire prevention in an ongoing basis.
Parts of the code reference other codes including the International Plumbing Code, the International Mechanical Code, the National Electric Code, and various National Fire Protection Association Standards.
IBC is more descriptive and also includes A or B types of construction for each class.
A is protected, meaning that all structural members of a building or structure have an additional fire rated coating or cover by means of sheetrock, spray on, or other approved method.
The additional fire rated coating or cover extends the fire resistance of the structural members by at least 1 hour.
B is unprotected, meaning that all structural members of a building or structure have no additional fire rated coating or cover.
Exposed members are only fire resistant according to their natural ability, characteristics, and fire rating.
Insurance Services Office (ISO):
This is a provider of data, underwriting, risk management, and legal/regulatory services to property-casualty insurers and other clients. -
Step 3: we must therefore know the following composition of the building elements: Structural frame Bearing walls (interior and exterior) Floor construction Roof construction What the fire rating of the materials
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Step 4: Building classes: All construction types must be classified into the following (all of which are explained extensively below): Frame Construction (ISO Class I
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Step 5: IBC Type V) Joisted Masonry (ISO Class 2
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Step 6: IBC Type III
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Step 7: IBC Type IV) Light Noncombustible (ISO Class 3
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Step 8: IBC Type IIB) Masonry Noncombustible (ISO Class 4
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Step 9: IBC Type IIA) Modified Fire Resistive (ISO Class 5
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Step 10: IBC Type IB) Fire Resistive (ISO Class 6
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Step 11: IBC Type IA)
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Step 12: International Building Code (IBC) versus Insurance Services Office (ISO): These are two major sources identifying construction types
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Step 13: both of which will be addressed in the construction types outlined below.
Detailed Guide
Classification of a building class is based on two factors: building elements and fire-resistance rating.
These factors may not be included in the submission/documentation, in which case additional information will need to be requested.
Building elements:
The building materials used in the construction of the following elements are the foundation for classification, be they wood, steel, or masonry.
Structural frame Exterior bearing walls Interior bearing walls Exterior nonbearing walls and partitions Interior non-bearing walls and partitions Floor construction, including supporting beams and joists Roof construction, including supporting beams and joists, are comprised of Fire-resistance rating:
This is the other factor in determining construction class.
The building materials used in the construction of the building elements above will have a fire-resistance rating.
Fire-resistance rating typically means the duration for which a passive fire protection system can withstand a standard fire resistance test.
This can be quantified simply as a measure of time (ex. 0 hours, 1 hour, or 2 hours), or it may entail a host of other criteria involving other evidence of functionality or fitness for purpose. “Minimum” rule:
It is important to remember when selecting the construction class that the building is only as strong as its weakest element.
For example, a masonry building may have an unprotected wood roof.
The wood roof is the weakest member such that it has no fire-resistance.
Thus, the construction class would be Joisted Masonry (see below).
Now imagine this same building with a metal deck roof.
So long as the supporting members of the building do not contain wood then this building would be Masonry Noncombustible (see below).
,, ISO is traditionally what insurance companies use to denote type, whereas IBC is what architects and builders use.
While one company may use ISO classifications, many submission documents may reference IBC classifications and it is important to be able to convert this to an ISO classification. (There have been situations where a frame building has been incorrectly classified as fire resistive because the submittal was read incorrectly!) The following explains what is expected under both:
International Building Code (IBC):
This is a model building code developed by the International Code Council (ICC).
It has been adopted throughout most of the United States.
A large portion of the International Building Code deals with fire prevention.
It differs from the related International Fire Code in that the IBC handles fire prevention in regards to construction and design and the fire code handles fire prevention in an ongoing basis.
Parts of the code reference other codes including the International Plumbing Code, the International Mechanical Code, the National Electric Code, and various National Fire Protection Association Standards.
IBC is more descriptive and also includes A or B types of construction for each class.
A is protected, meaning that all structural members of a building or structure have an additional fire rated coating or cover by means of sheetrock, spray on, or other approved method.
The additional fire rated coating or cover extends the fire resistance of the structural members by at least 1 hour.
B is unprotected, meaning that all structural members of a building or structure have no additional fire rated coating or cover.
Exposed members are only fire resistant according to their natural ability, characteristics, and fire rating.
Insurance Services Office (ISO):
This is a provider of data, underwriting, risk management, and legal/regulatory services to property-casualty insurers and other clients.
About the Author
Jose Lee
Specializes in breaking down complex crafts topics into simple steps.
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