1/2 hour rated fire partition using Calculated fire resistance.

[Fast_Edd1e]

Michigan Building Code 2015. Vb construction fully fire suppressed. Apartments. We only need a 1/2 hour rating on the separation between corridor and apartment.

We have an issue where they have installed the tub enclosure of the apartment on the corridor wall. There is no drywall behind it so only the corridor side has gyp. We are trying to use section 722 of calculated fire resistance that we can use 1 layer of 5/8" gyp board which has a 30 minute rating on the corridor side. That would make a 1/2 hour separation between the two. We will even double it if it helps.

Inspector is saying we need to protect from both sides.

Is there any section I can look at that says what side of the partition needs the protection? These are non-load bearing interior walls. I know there is a National Gypsum (2) layer asymetrical rated wall, but its metal stud. Which is why im trying to look at the "calculated fire resistance" since we are under 1 hour required separation.

 

[steveray]

703.2.1.1 Nonsymmetrical Wall Construction​

Interior walls and partitions of nonsymmetrical construction shall be tested with both faces exposed to the furnace, and the assigned fire-resistance rating shall be the shortest duration obtained from the two tests conducted in compliance with ASTM E119 or UL 263. Where evidence is furnished to show that the wall was tested with the least fire-resistant side exposed to the furnace, subject to acceptance of the building official, the wall need not be subjected to tests from the opposite side (see Section 705.5 for exterior walls).

 

[RLGA]

The inspector is correct. Section 722.6.2.1 requires the calculation to be based on the membrane on the exposed side plus the framing--you cannot include the membrane on the unexposed side. Thus, using studs only on the room side provides only 20 minutes--something else needs to be added.

 

[Fast_Edd1e]

To add to this. If im using 722 calculated fire resistance. Wood studs 16" o.c. have an assigned 20 miuntes to the frame. If i fill the stud cavity with approved insulation i can get another 15 minutes. Then with 5/8 on the corridor side. That gives me nearly an hour. And this is only where the tub is, so only a few feet of that wall.

 

[Fast_Edd1e]

The inspector is correct. Section 722.6.2.1 requires the calculation to be based on the membrane on the exposed side plus the framing--you cannot include the membrane on the unexposed side. Thus, using studs only on the room side provides only 20 minutes--something else needs to be added.

What if I add instulation which gives me another 15?

I know the proper way is to pull the tubs and adjust the plumbing. But im getting asked to see if there are alternatives.

 

[steveray]

Kind of funny..it almost assumes a membrane on the exposed side but doesn't technically mandate it....

722.6.2.1 Fire-Resistance Rating of Wood Frame Assemblies​

The fire-resistance rating of a wood frame assembly is equal to the sum of the time assigned to the membrane on the fire-exposed side, the time assigned to the framing members and the time assigned for additional contribution by other protective measures such as insulation.

 

[Fast_Edd1e]

Kind of funny..it almost assumes a membrane on the exposed side but doesn't technically mandate it....

722.6.2.1 Fire-Resistance Rating of Wood Frame Assemblies​

The fire-resistance rating of a wood frame assembly is equal to the sum of the time assigned to the membrane on the fire-exposed side, the time assigned to the framing members and the time assigned for additional contribution by other protective measures such as insulation.

That is what I was thinking. It doesnt really say both sides need a membrane.

I did see in a commentary. "the membrane on the unexposed side is not included in the calculations. It is assumed that once the strucral members fail, the entire assembly fails.

So my interpretation would be that the 5/8" on one side protects both sides from the fire as it cant pass thru. And the stud with insulation provides 35 minutes. Because if it fails, the whole assembly fails.

 

[Fast_Edd1e]

That is what I was thinking. It doesnt really say both sides need a membrane.

I did see in a commentary. "the membrane on the unexposed side is not included in the calculations. It is assumed that once the strucral members fail, the entire assembly fails.

So my interpretation would be that the 5/8" on one side protects both sides from the fire as it cant pass thru. And the stud with insulation provides 35 minutes. Because if it fails, the whole assembly fails.

And with this concept. There it technically, while not rated, a fiberglass membrane on the inside face that is protecting the stud and insulation.

 

[RLGA]

Before we take this discussion any further, let me ask these simple questions:

1. Did the drawing details show the gypsum board continuously behind the tubs?
2. If the answer is "no" to #1, did the drawings identify this wall as a specific wall type in the drawings (i.e., gypsum board on both sides of framing with insulation)?
3. If the answer is "yes" to #2, did the wall type indicate it was a 30-minute fire-resistance-rated wall?
4. If the answer is "yes" to #3, then the contractor did not follow the contract documents and is now asking you to find a solution to their mistake. Either have them remove the tubs and reinstall them after the gypsum board is installed correctly, or tell them you will invoice them at your hourly rate for the effort you put into finding an alternative solution. Assuming your hourly rate is around $200-$300, this could be a $2,000 to $3,000 (or more) cost out of the contractor's pocket. Depending on the number of tubs involved, this added expense could be the deciding factor.

 

[Fast_Edd1e]

Before we take this discussion any further, let me ask these simple questions:

1. Did the drawing details show the gypsum board continuously behind the tubs?
2. If the answer is "no" to #1, did the drawings identify this wall as a specific wall type in the drawings (i.e., gypsum board on both sides of framing with insulation)?
3. If the answer is "yes" to #2, did the wall type indicate it was a 30-minute fire-resistance-rated wall?
4. If the answer is "yes" to #3, then the contractor did not follow the contract documents and is now asking you to find a solution to their mistake. Either have them remove the tubs and reinstall them after the gypsum board is installed correctly, or tell them you will invoice them at your hourly rate for the effort you put into finding an alternative solution. Assuming your hourly rate is around $200-$300, this could be a $2,000 to $3,000 (or more) cost out of the contractor's pocket. Depending on the number of tubs involved, this added expense could be the deciding factor.

So yes. My drawings have a diagram stating what walls need to be 1/2 hour rated separation between apartments and corridor and showing where those walls are. Then i reference a typical ul 1 hour rated wood stud 5/8 gyp each side. So yes, they should have put up gyp first. I believe they are going to have to pull those and gyp behind the tub and adjust the tub drain. I do feel im grasping at straws to get this to work otherwise. And it is a little frustrating that it wasnt done. His excuse is that because it said 1/2 hour and 5/8 on one side gives 30 minutes, that it should be allowed.

 

[ICE]

Once a fiberglass tub surround is on fire the 35 minute rating of a wood stud and insulation will pick up speed. I have encountered this situation. Their argument is with an inspector that has been around the block.

His excuse is that because it said 1/2 hour and 5/8 on one side gives 30 minutes, that it should be allowed.

The age old assumption. People do that for a variety of reasons. For example, A hotel corridor. I was working pick-up. A plywood hanger asked me if the corridor was ready for him. I told him to ask the super. He didn't. A week later he was pulling it off. His excuse is that the super is a mean, gruff ass that nobody wanted anything to do with.. so rather than get crapped on he made a command decision (assumption)

 

[BN4537]

We are not trying to protect the dwelling from the hallway so much as the other way around. How many fires start in the hallway vs the dwelling? Regardless, both sides need to be done unless you can find some tested wall assembly that works. I guess you could build a thin shaftwall along the inside of the corridor and make the bathroom wall redundant...

Inspector is saying we need to protect from both sides.

Good work on his part.

Once a fiberglass tub surround is on fire the 35 minute rating of a wood stud and insulation will pick up speed. I have encountered this situation. Their argument is with an inspector that has been around the block.

Indeed...

 

[RLGA]

His excuse is that because it said 1/2 hour and 5/8 on one side gives 30 minutes, that it should be allowed.

That is not an excuse--that is a breach of contract. All changes to the contract documents must be approved by the architect and owner (if using AIA Contract Documents). His "assumption" just cost him time and money. Your role on the project is to ensure compliance with the contract documents--not to cover the contractor's a$$.

 

[jar546]

Did the drawing details show the gypsum board continuously behind the tubs?

Absolutely one of the most important questions to ask during plan review. So often this is missed.

 

[Yankee Chronicler]

To add to this. If im using 722 calculated fire resistance. Wood studs 16" o.c. have an assigned 20 miuntes to the frame. If i fill the stud cavity with approved insulation i can get another 15 minutes. Then with 5/8 on the corridor side. That gives me nearly an hour. And this is only where the tub is, so only a few feet of that wall.

Some years ago a PE friend of mine (since deceased) expressed it this way: "The building code is the minimum standard for a safe building. You want to do less than what the code requires, so by definition you don't want a safe building. The only remaining question is how unsafe you want your building to be."

 

[Yankee Chronicler]

That is what I was thinking. It doesnt really say both sides need a membrane.

I did see in a commentary. "the membrane on the unexposed side is not included in the calculations. It is assumed that once the strucral members fail, the entire assembly fails.

So my interpretation would be that the 5/8" on one side protects both sides from the fire as it cant pass thru. And the stud with insulation provides 35 minutes. Because if it fails, the whole assembly fails.

As has been pointed out, the bathroom is the exposed side, not the unexposed side.

 

[Yankee Chronicler]

So yes. My drawings have a diagram stating what walls need to be 1/2 hour rated separation between apartments and corridor and showing where those walls are. Then i reference a typical ul 1 hour rated wood stud 5/8 gyp each side. So yes, they should have put up gyp first. I believe they are going to have to pull those and gyp behind the tub and adjust the tub drain. I do feel im grasping at straws to get this to work otherwise. And it is a little frustrating that it wasnt done. His excuse is that because it said 1/2 hour and 5/8 on one side gives 30 minutes, that it should be allowed.

What is your role? Are you the architect? Why are you grasping at straws to get something approved that clearly doesn't meet code and apparently doesn't comply with the plans you drew?

If this kind of confusion can occur, it seems pretty clear to me (both as an architect and as a building official) that your drawings were incomplete.

Michigan building code:

[A] 107.2.1 Information on Construction Documents. Construction documents shall be dimensioned and drawn upon suitable material. Electronic media documents are permitted to be submitted where approved by the building official. Construction documents shall be of sufficient clarity to indicate the location, nature and extent of the work proposed and show in detail that it will conform to the provisions of this code and relevant laws, ordinances, rules and regulations, as determined by the building official.

Detroit building code:

[A] 107.2.1 Information on Construction Documents. Construction documents shall be dimensioned and drawn upon suitable material. Electronic media documents are permitted to be submitted where approved by the building official. Construction documents shall be of sufficient clarity to indicate the location, nature and extent of the work proposed and show in detail that it will conform to the provisions of this code and relevant laws, ordinances, rules and regulations, as determined by the building official.

 

[TheCommish]

Designer decided the results wanted, designer draws the picture of the desired results, BO reviews the picture for code compliance, picture complies with code. Permit issued for project based on the picture, contractors build the picture, all is well.

Now contractors want to build something different than the picture, submits new picture to designer, process starts over.

 

[Yankee Chronicler]

Designer decided the results wanted, designer draws the picture of the desired results, BO reviews the picture for code compliance, picture complies with code. Permit issued for project based on the picture, contractors build the picture, all is well.

Now contractors want to build something different than the picture, submits new picture to designer, process starts over.

But it does not appear that the designer drew a picture of the required fire-resistance rated assembly. What Fast_Edd1e wrote was:

My drawings have a diagram stating what walls need to be 1/2 hour rated separation between apartments and corridor and showing where those walls are. Then i reference a typical ul 1 hour rated wood stud 5/8 gyp each side.

To me, that says he drew a key plan showing certain walls as having a 1/2-hour rating, and somewhere he had a note saying that a 1/2-hour rated wall should be a U.L. X### assembly. This means it can't be constructed from the "construction drawings," the builder (or his guys on the site) have to have access to some kind of a computer and go on-line to look up what a U.L. X### assembly is.

IMHO, this approach does not meet the basic requirement of IBC 107.2.1, which I cited above. It's a common approach. I see a LOT of plans on which the designer (or drafter) tried to take shortcuts and pass the buck for making design decisions down to the guys on the site. That's not what the code calls for. The guy swinging the hammer should not need to have a code book on the site. He should be able to open up the plans and find ALL the information he needs to build the building in complete compliance with the applicable codes.

 

[RLGA]

But it does not appear that the designer drew a picture of the required fire-resistance rated assembly. What Fast_Edd1e wrote was:



To me, that says he drew a key plan showing certain walls as having a 1/2-hour rating, and somewhere he had a note saying that a 1/2-hour rated wall should be a U.L. X### assembly. This means it can't be constructed from the "construction drawings," the builder (or his guys on the site) have to have access to some kind of a computer and go on-line to look up what a U.L. X### assembly is.

IMHO, this approach does not meet the basic requirement of IBC 107.2.1, which I cited above. It's a common approach. I see a LOT of plans on which the designer (or drafter) tried to take shortcuts and pass the buck for making design decisions down to the guys on the site. That's not what the code calls for. The guy swinging the hammer should not need to have a code book on the site. He should be able to open up the plans and find ALL the information he needs to build the building in complete compliance with the applicable codes.

Only some things have to be detailed. Since we have yet to determine exactly how the wall assembly was presented in the drawings, it is hard to criticize the OP's method.

It is very common to show partition types that illustrate the make-up of each partition, and if a partition is required to be rated, the applicable designation is provided. Contractors have just as much access to UL assemblies as architects do in this digitally connected world. References to industry standards are frequently used without providing the contractor with a copy of every applicable standard. In many cases, the subcontractors and installers know more about the industry standards for their respective specialties than the architects who reference them. I am sure any quality framing and drywall subcontractor is quite familiar with common UL assemblies, such as UL U465 and U305.

I have been writing specifications for over 25 years, and not once have I specified the specific nail or screw patterns for each type of assembly--I essentially refer to the assembly identified on the drawings. This requires the contractor/subcontractor to obtain a copy of the assembly to follow the installation requirements exactly as prescribed in the approved assembly descriptions. Some architects will make it easy for the contractor/subcontractor by including the assembly documents in their construction documents; however, that could be problematic sometimes, especially for public projects.

UL, FM, and other testing authorities provide assemblies that are frequently very proprietary, and if a public or private owner requires open competition, proprietary construction documents are not permitted. Therefore, designers may use one system as a "basis of design," allowing for comparable products to be submitted by the contractor/subcontractor. If the contractor/subcontractor wanted to use something other than the basis-of-design system, they would be required to provide suitable alternative assemblies. Thus, the contractor/subcontractor would need to have enough familiarity with the IBC, UL, GA, or other acceptable sources to propose alternative assemblies that comply with the requirements of the contract documents. It could be counter-productive for the designer to over-detail a project because you may never know what you will get when construction begins.

 

[dbartley]

Only semi-related: Does Michigan building code not require STC 50 walls?