Type IIIa Const. - Wood framed stage over conc. floor

[tahoebrian5]

Hi all, glad to find this forum and this is my first post. I am a civil (struct discipline) engineer and have an interesting issue.

A client was red-tagged for building a stage in an existing building of type IIIa construction (concrete floors and perimeter walls). The space is a dance hall.
The stage was built from wood joists and plywood. From what I can see floors need to be a 1 hour rated assembly in IIIa.

My question is: Does this apply to a stage that is built over a concrete slab?

There is also a ramp at one of the exits that has the same issue.

I have a call into the building department but thought it would be interesting to see if there are any thoughts or other considerations out there. Is there a case that the raised stage is not a "floor" and therefore this would not apply?

Thx!

 

[Tim Mailloux]

410.2.1 Stage construction. Stages shall be constructed of materials as required for floors for the type of construction of the building in which such stages are located.

Exception: Stages need not be constructed of the same materials as required for the type of construction provided that the construction complies with one of the following:

1. Stages of Type IIB or IV construction with a nominal 2-inch (51 mm) wood deck, provided that the stage is separated from other areas in accordance with Section 410.2.4.

2. In buildings of Type IIA, IIIA and VA construction, a fire-resistance-rated floor is not required, provided that the space below the stage is equipped with an automatic sprinkler system or fire-extinguishing system in accordance with Section 903 or 904.

3. In all types of construction, the finished floor shall be constructed of wood or approved noncombustible materials. Openings through stage floors shall be equipped with tight-fitting, solid wood trap doors with approved safety locks.

 

[Joe.B]

A client was red-tagged for building a stage in an existing building

Going out on a limb here, maybe he was "red-tagged" for doing work without a permit?

Usually, an issue like this would come up in the permitting process, instead of after they've done the work... Not always, granted, but that's the idea anyways.

 

[bill1952]

Hi all, glad to find this forum and this is my first post. I am a civil (struct discipline) engineer and have an interesting issue.

A client was red-tagged for building a stage in an existing building of type IIIa construction (concrete floors and perimeter walls). The space is a dance hall.
The stage was built from wood joists and plywood. From what I can see floors need to be a 1 hour rated assembly in IIIa.

My question is: Does this apply to a stage that is built over a concrete slab?

There is also a ramp at one of the exits that has the same issue.

I have a call into the building department but thought it would be interesting to see if there are any thoughts or other considerations out there. Is there a case that the raised stage is not a "floor" and therefore this would not apply?

Thx!

Are you sure it's not a platform, and not a stage? 410.3 has requirements for a platform that are less destructive.

I have a difficult time thinking a raised floor area for musicians in a dance hall is not clearly a platform.

 

[tahoebrian5]

Okay I believe bill1951 is correct, this is a platform not a stage. And yes Joe, this was red-tagged due to unpermitted construction.

Thank you Tim, those are helpful links. My conclusion is I need to use a 1 hour assembly but the bottom side does not necessarily need to be protected per 410.3.

Can anyone recommend a wood framed floor assembly that does not have a bottom layer? Ideally without gypcrete topping. I expect the contractor would prefer multiple layers to topping slab and its only about 24" finish floor height so going to be tough to get a bottom layer installed.

 

[bill1952]

Reread 410.3. For some reason I can't paste here - maybe my phone - but I'm not sure the option to not protect the bottom of the floor in last sentence isn't applicable whether or not you use FRT lumber.

Look into a layer of Structocrete with flooring - ply or other - on top of it. Might be easier than putting something under.

Strictly from a non-code point of view, they may find an undesirable "drumming" effect. Sides should be copiously vented and dense fibreglass or rock wool on under side will help some.

 

[Tim Mailloux]

based on my reading of 410.3, the platform floor construction would need to be 1 hour rated per table 601.


410.3 Platform construction.
Permanent platforms shall be constructed of materials as required for the type of construction of the building in which the permanent platform is located. Permanent platforms are permitted to be constructed of fire-retardant-treated wood for Types I, II and IV construction where the platforms are not more than 30 inches (762 mm) above the main floor, and not more than one-third of the room floor area and not more than 3,000 square feet (279 m2) in area. Where the space beneath the permanent platform is used for storage or any purpose other than equipment, wiring or plumbing, the floor assembly shall be not less than 1-hour fire-resistance-rated construction. Where the space beneath the permanent platform is used only for equipment, wiring or plumbing, the underside of the permanent platform need not be protected.

Commentary
This section establishes the scope of the code requirements for platform construction. A permanent platform is basically raised floor construction. As such, the construction must be consistent with that of all the floors in the building. Permanent platforms can be of fire-retardant-treated wood in limited applications. In buildings of Type I, II or IV construction, platforms can be of fire-retardant-treated wood where they are not more than 30 inches (762 mm) in height, are not more than one-third of the floor area of the room and are 3,000 square feet (279 m2) or less in area. A platform that meets these three size limits poses a small fire risk relative to the normal fuel load in the room. As such, the platform deck and its supporting construction can be of fire-retardant-treated wood materials. Where the platform exceeds any one of the three size limits, it must be constructed of materials consistent with the building’s type of construction classification. A basic premise of Section 410.3 is that the platform must not significantly increase the fire hazard of the space or building. As such, the space beneath platforms is regulated to appropriately abate the risk. Where the space beneath a permanent platform is utilized for any purpose other than electrical wiring or plumbing, the platform is to have a 1-hour fire-resistance rating. The purpose of the fire-resistance-rating requirement is to provide some structural integrity to the platform should a fire occur in the concealed space. In the case of permanent platforms where the space beneath the platform is only used for plumbing or electrical wiring, no further protection is required since the fire risk will be minimal.

 

[steveray]

based on my reading of 410.3, the platform floor construction would need to be 1 hour rated per table 601.


. Where the space beneath the permanent platform is used only for equipment, wiring or plumbing, the underside of the permanent platform need not be protected.

Commentary
The purpose of the fire-resistance-rating requirement is to provide some structural integrity to the platform should a fire occur in the concealed space. In the case of permanent platforms where the space beneath the platform is only used for plumbing or electrical wiring, no further protection is required since the fire risk will be minimal.

Not that I like it but......They must not know a lot of plumbers and electricians...

 

[Tim Mailloux]

Not that I like it but......They must not know a lot of plumbers and electricians...

I read the 1 hour floor requirement stated in 410.3 to be in addition to any requirements based on construction type. As an example, if you have IIB construction which does not require a rated floor, 410.3 could require that the platform floor have a 1hour rating even though table 601 does not require it.

 

[steveray]

I read the 1 hour floor requirement stated in 410.3 to be in addition to any requirements based on construction type. As an example, if you have IIB construction which does not require a rated floor, 410.3 could require that the platform floor have a 1hour rating even though table 601 does not require it.

Correct....Not required to be rated "because it is a platform" with no storage (but would be required to be rated by construction type)....Not required to be rated as a floor in IIIA (stage) as it will have sprinklers under it (if it is a stage)...But this is more of the weirdness with stages vs. platforms that Bill will fix at some point....

 

[Tim Mailloux]

Correct....Not required to be rated "because it is a platform" with no storage....Not required to be rated as a floor in IIIA as it will have sprinklers under it (if it is a stage)...But this is more of the weirdness with stages vs. platforms that Bill will fix at some point....

but wouldn't it be required to be rated because its a platform in type IIIA construction, and type IIIA construction requires 1 hour rated floors?

 

[steveray]

but wouldn't it be required to be rated because its a platform in type IIIA construction, and type IIIA construction requires 1 hour rated floors?

Not if it is a stage...

2. In buildings of Type IIA, IIIA and VA construction, a fire-resistance-rated floor is not required, provided that the space below the stage is equipped with an automatic sprinkler system or fire-extinguishing system in accordance with Section 903 or 904.

 

[Tim Mailloux]

Not if it is a stage...

but if its a platform it does?

 

[steveray]

but if its a platform it does?

Doesn't seem like it should, but.....The way you read 410.3 doesn't seem to give it a pass....

 

[bill1952]

There are many things in section 410 that are antiquated, illogical, or just poorly written. I live in that chapter, have been a proponent for some of what's there now, and wince when I read it. The stuff from 1990s is better than what was there before, but not good.

I had 11 proposals heard in April (1 AS, 10 R) and now 10 comments for this October, maybe a little headway. Becoming a bucket list mission. Oh, and next Tuesday same issues in committee meeting for NFPA 101 and 5000.

 

[steveray]

There are many things in section 410 that are antiquated, illogical, or just poorly written. I live in that chapter, have been a proponent for some of what's there now, and wince when I read it. The stuff from 1990s is better than what was there before, but not good.

I had 11 proposals heard in April (1 AS, 10 R) and now 10 comments for this October, maybe a little headway. Becoming a bucket list mission. Oh, and next Tuesday same issues in committee meeting for NFPA 101 and 5000.

The struggle is real....I went through 70 IRC proposals Tuesday morning....Thank you for what you do...

 

[bill1952]

The system doesn't lend itself to "big" changes. Like my section 410, would have been more productive and efficient to sit around a table (or web version) and discuss. Having to break it into little pieces and then get a few minutes to testify and no option to discuss and deliverate. It may work fine to change from 30 minutes to an hour, or edit for a new product, or simple changes, but not big ones. I attached a lot of resource documents to my proposals and I'm not sure any of the voting committee read any of them - and I get that. They're volunteering. Was frustrating when they said I should have shown them what it would look like if all accepted. I had attached a preprint. Not faulting the individuals, but the system.