ICF FIREWALL

[mtldesigns]

I have a ICF build duplex going through the permitting phase, and it keeps getting kicked back because of the firewall.  I am wits end on this. We are using Nudura 6" blocks and they provided the nice Fire Wall Details, that I attached to my layout sheet.  The building department wants us to double the Type "X" board on the firewall itself (that separates the units).  AND double on the north/south exterior walls, since we are less than 10' from the nearest structure.  YES, they want double X under the lap siding.  I have never ever heard of such a thing.  Does this make sense to anyone? 

 

I attached a couple of the details, but here is the the link to these and more firewall details from Nudura, if anyone is interested

 

https://www.nudura.com/resources/design-library/fire-wall/  

fw6d2b.pdf

fw6d3.pdf

[Greg_NY61]

I heard plenty of that in certain situations... How far is the house from the property line? It could be a local requirement, some fire codes want firewalls if less than 5' from the property line some more. Just add what they require and move on unless you find something that you can fight them with, but even if you do, it could be local jurisdiction and requirement and nothing you can do.

[robdyck]

9 hours ago, mtldesigns said:

Does this make sense to anyone?

It doesn't! You may need to be in discussion with the permitting authority so they can explain their perspective as to why the EPS insulation covering your 2 hour wall (the concrete core) needs such a high level of protection. If the building were built with CMU, or cast-in-place concrete, would an exterior insulation layer of XPS or EPS require the same level of protection?

I'm not sure where this building is, but a 1 hour wall is all that's required, correct? And, most 6" ICF's have a 2-4 hour rating with the added benefit of the protective layer being continuous (no gaps, construction joints, etc.).

I can tell you from my own experience in several jurisdictions in Canada that many inspectors just treat ICF differently due to a lack of familiarity. There's just something about the insulation and lightweight block idea that makes them forget that it's a solid concrete wall!!

I'd recommend an in-person meeting if possible and make sure that you contact Nudura in advance. They may have even more documentation available to present to the permitting official.

[robdyck]

10 hours ago, mtldesigns said:

We are using Nudura 6" blocks and they provided the nice Fire Wall Details, that I attached to my layout sheet.

This is what you want to provide. Read Note #4 (near the end) and that will explain why they want 2 layers of 5/8" at the exterior walls.

https://www.nudura.com/media/1169/nudura-r21415-bxuvcwo12-cdn-frr-listing-2014.pdf

[joey_martin]

I'm with Rob, someone isn't looking at the fact that this structure has a 6" concrete core. New guy in the office or first time dealing with an ICF?

[rlackore]

12 hours ago, mtldesigns said:

Does this make sense to anyone? 

 

No. Isn't Florida's residential code based on the IRC? Referring the local officials to R302.3, and providing the Nudura details and listed details, should be sufficient to make your case. 

 

2 hours ago, robdyck said:

This is what you want to provide. Read Note #4 (near the end) and that will explain why they want 2 layers of 5/8" at the exterior walls.

https://www.nudura.com/media/1169/nudura-r21415-bxuvcwo12-cdn-frr-listing-2014.pdf

 

Note #4 only requires 1/2" type-x; if you're not using the 1/2" type-x, then you can use 1" of a concrete masonry product.

[robdyck]

2 minutes ago, rlackore said:

Note #4 only requires 1/2" type-x; if you're not using the 1/2" type-x, then you can use 1" of a concrete masonry product.

I'm just saying this may explain the reasoning. Maybe, maybe not, how would I know?:)

 

 

When the Insulated Concrete Wall is used as an exterior wall, in order for the Fire Resistance Rating to remain valid from both sides of the wall, the gypsum wallboard on the exterior face of the exterior wall may be substituted with minimum 25 mm thick concrete or masonry mechanically fastened to the supporting Insulated Concrete Wall independent of the EPS insulation.

[rlackore]

6 minutes ago, robdyck said:

I'm just saying this may explain the reasoning. Maybe, maybe not, how would I know?:)

 

 

When the Insulated Concrete Wall is used as an exterior wall, in order for the Fire Resistance Rating to remain valid from both sides of the wall, the gypsum wallboard on the exterior face of the exterior wall may be substituted with minimum 25 mm thick concrete or masonry mechanically fastened to the supporting Insulated Concrete Wall independent of the EPS insulation.

 

Sure, fair enough. Maybe I'm giving the plan reviewer too much credit for being able to determine the minimum requirement within the context of the entire paragraph.

[robdyck]

12 minutes ago, rlackore said:

Sure, fair enough. Maybe I'm giving the plan reviewer too much credit for being able to determine the minimum requirement within the context of the entire paragraph.

@mtldesigns

I think it's time for us to get the plan reviewer on a Zoom and see if we can't get this figured out. What time works best for y'all? 

 

[mtldesigns]

10 hours ago, robdyck said:

It doesn't!

 

8 hours ago, joey_martin said:

New guy in the office or first time dealing with an ICF?

 

8 hours ago, rlackore said:

No. Isn't Florida's residential code based on the IRC? Referring the local officials to R302.3, and providing the Nudura details and listed details, should be sufficient to make your case. 

Thank you all for your input.  I wrote this inspector a nice long email last night, after I summitted this question to you guys.  The Nudura 6" core is a 4 hour rating, all by itself.  I highlighted the Type X callouts with a border around that text on the Nudura details.  And asked in this email why TWO layers of this X was needed.  I can see maybe a stud wall, but a concrete core wall, scratching my head.  However, I did not add any Type X under the exterior lap siding, but did add on the interior of the north and south walls.  That wall is also a 4 hour wall.  We resubmitted last night along with my email.  Waiting for their response.    

 

 

8 hours ago, rlackore said:

Note #4 only requires 1/2" type-x; if you're not using the 1/2" type-x, then you can use 1" of a concrete masonry product.

 

Could Hardie board be considered the concrete exterior?  Its cement based...

 

 

[rlackore]

14 minutes ago, mtldesigns said:

Could Hardie board be considered the concrete exterior?  Its cement based...

 

I would say no.

[robdyck]

22 minutes ago, rlackore said:

 

I would say no.

Ditto.

[mtldesigns]

I didn't think so, but the masonry min. had me thinking.   

 

I attached the detail with my added notes.. this is what I re-submitted last night.

[rlackore]

Looking at your detail, if I were the plan reviewer, I'd want to know how you're achieving a 1-hour rating on the underside of the eave. The soffit detail I prefer uses two layers of 5/8" glass-mat gypsum panel (or equivalent), edge joints staggered and blocked, with an intumescent fire caulk where it butts against the 1-hour exterior wall assembly.

[Northriver]

It needs to have an ASTM, UL testing number. Any company can draw a detail claiming fire resistance but if it has no testing certification it means nothing. I went thru the same thing 5 years ago and per the IRC and IBC to be considered fire rated it must have testing documentation to back it up. Call the company up and ask for the testing information. Usually it's ASTM or UL number.

[mtldesigns]

3 hours ago, Northriver said:

Call the company up and ask for the testing information

Nudura had all the testing data and that was presented.  And as of yesterday, the permit was signed.  

 

Thanks for all the help gents.  I have a new client in the same neighborhood, and even though its not a duplex, its close to neighbors homes and wood framed.  Lesson learned form this and all your advice.