ISO Class III...??? (or I)

[Mark Forman]

hello again...

In my travels this week, I inspected a building that had:

Steel Roof Trusses
Metal Stud Exterior Walls, sheetrocked on the inside; & sided w/ T1-11 wood panels on the exterior (at least I believe they were metal studs...looked like 2X6 nominal...maybe cold-formed load bearing exterior wall metal studs?)
The building was constructed in the 1990's (according to the insured).

Is this an ISO Class III (light non-combustible)...???...or is it ISO Class I simply because it's frame construction?

(reason I'm asking is...I've never come across steel roof trusses on a frame building)

thanx,

MF

[Jerry Peck]

Is this an ISO Class III (light non-combustible)...???...or is it ISO Class I simply because it's frame construction?

(reason I'm asking is...I've never come across steel roof trusses on a frame building)

My first question is - Why are you asking the ISO Classification? For what purpose?

After that, you did not give enough information - here are some links which may either help or confuse the matter (based on what is written as what is Class I and Class III):

http://www.upfro.com/Inspectors/ISO%20Consturction%20Class.htm (note that Class I says "light-gauge metal)

https://www.guc.com/Data/Sites/1/media/design-manual/2008-updates/b2-construction%20class%20definitions.pdf

https://www.irmi.com/docs/default-source/afis-handouts/building-construction-classifications-understanding-iso-classification.pdf?sfvrsn=6

http://www.amrisc.com/Amrisc%20pdfs/CompleteSOV/ISOTypesDescriptions.pdf

https://www.sorm.state.tx.us/wp-content/uploads/2017/06/Construction%20and%20Occupancy%20Classification.pd f (may be the best help as it provides a relationship to the building code types of construction)

I would start be finding out what type of construction the building is, then use the last one above to relate that to the ISO Classification.

However, as a home inspector, if you are a home inspector, why are your identifying ISO Class/Type of Construction?

[Steve Payson]

ISO 1 - Frame Construction (Wood walls & Roof, foundation construction does not matter) Masonry Veneer or accents still count as ISO 1.

ISO 2 - Joisted Masonry - Free standing Masonry shell with wood floors and joists, flammable roof. (If structure burns, masonry walls remain)

ISO 3 - Light noncombustible - Structure does not add to fire (fuel) load of building but does not resist fire well. Light steel construction.

ISO 4 - Masonry Noncombustible - Free standing masonry walls with noncombustible floors and roof.

ISO 5 - Modified Fire Resistive - Walls between fire divisions in structure have 1-hour fire rating. Noncombustible structure.

ISO 6 - Fire Resistive - Walls between fire divisions have 2-hour fire rating, otherwise noncombustible structure.

[Jerry Peck]

ISO 1 - Frame Construction (Wood walls & Roof, foundation construction does not matter) Masonry Veneer or accents still count as ISO 1.

ISO 2 - Joisted Masonry - Free standing Masonry shell with wood floors and joists, flammable roof. (If structure burns, masonry walls remain)

ISO 3 - Light noncombustible - Structure does not add to fire (fuel) load of building but does not resist fire well. Light steel construction.

ISO 4 - Masonry Noncombustible - Free standing masonry walls with noncombustible floors and roof.

ISO 5 - Modified Fire Resistive - Walls between fire divisions in structure have 1-hour fire rating. Noncombustible structure.

ISO 6 - Fire Resistive - Walls between fire divisions have 2-hour fire rating, otherwise noncombustible structure.

Source?

[Steve Payson]

Source?

I used to do commercial risk management & loss control inspections back in the day and what I posted above (although it can get more detailed based on hourly fire resistance ratings) is what every insurance company I dealt with used to determine ISO class.

https://www.assetworks.com/wp-content/uploads/2016/04/ISO_Construction_Classifications.pdf

https://www.sorm.state.tx.us/wp-content/uploads/2017/06/Construction%20and%20Occupancy%20Classification.pd f

By the way, I never came across any insurance company that included "light-gauge metal" to qualify a structure to be in the ISO 1 classification.