Key Change to Ice Barrier Requirements in the 2024 IRC: What You Need to Know

[jar546]

Key Change to Ice Barrier Requirements in the 2024 IRC: What You Need to Know​

A significant update is coming to the 2024 International Residential Code (IRC) that affects how ice barriers are installed on steep-sloped roofs. Specifically, Section R905.1.2, which governs the use of ice barriers, has been revised to remove a requirement that applied to roofs with a slope of 8:12 or greater.

Previously, the code mandated that on these steeper roofs, the ice barrier had to extend at least 36 inches up the slope from the eave edge. This provision has now been removed. So, what’s the reasoning behind this change? According to the proposal led by Aaron Phillips of the Asphalt Roofing Manufacturers Association (ARMA), this guideline was not always practical and often led to confusion. The intent of the original rule was to address potential ice dams forming at the point where the roof's temperature drops below freezing. However, building characteristics, roof designs, and other variables make this 8:12 rule less relevant, and in some cases, it could actually leave sections of the roof unprotected from ice damming.

Instead of this specific slope-related guideline, the updated code ensures that the ice barrier is applied from the lowest edge of the roof to at least 24 inches inside the exterior wall line of the building. This approach provides a more consistent level of protection, no matter the roof's slope, by focusing on where ice dams are most likely to form.

For those of us enforcing or interpreting code, this change reduces potential confusion. The previous language about applying ice barriers "also" on steeper roofs sometimes led to interpretations that required two layers of protection—one running along the slope and one extending inside the exterior wall line. By eliminating this, the 2024 IRC simplifies the requirements and ensures a uniform installation approach that better reflects modern roofing practices.

As for the cost impact, this revision is expected to be neutral overall. In cases where the old provision was interpreted to require additional layers of ice barrier on steep roofs, there may be a cost reduction. On the other hand, situations where roofs now require more coverage to meet the 24-inch inside-the-wall rule might see a slight increase. But on balance, the change doesn’t significantly alter construction costs.

This update reflects a smarter, clearer approach to protecting buildings in cold climates, ensuring ice barriers are installed where they’ll be most effective, regardless of the roof's slope. For building officials and code professionals, it’s a straightforward change that aligns the IRC with best practices for ice dam prevention.

 

[steveray]

And he is right.....There is way less risk of ice dams on a 12/12 than a 5/12.....I don't love the exception as it begs the question, what happens when you convert? Just like the Vapor Barrier in a garage floor....

R905.1.2​

In areas where there has been a history of ice forming along the eaves causing a backup of water as designated in Table R301.2, an ice barrier shall be installed for asphalt shingles, metal roof shingles, mineral-surfaced roll roofing, slate and slate-type shingles, wood shingles and wood shakes. The ice barrier shall consist of not fewer than two layers of underlayment cemented together, or a self-adhering polymer-modified bitumen sheet shall be used in place of normal underlayment and extend from the lowest edges of all roof surfaces to a point not less than 24 inches (610 mm) inside the exterior wall line of the building.

On roofs with slope equal to or greater than 8 units vertical in 12 units horizontal (67-percent slope), the ice barrier shall be applied not less than 36 inches (914 mm) measured along the roof slope from the eave edge of the building.

Exception: Detached accessory structures not containing conditioned floor area.

Odd...ICC doesn't really show this as a change....Maybe clerical on their end?

 

[Energystar]

A related question. The Ice Barrier does not solve the ice-damming problem, it just helps to prevent damage. What if one uses raised-heel trusses such that the insulation level over the wall is at least R-30. Wouldn't this negate the need for the Ice Barrier per R104.11?

 

[steveray]

A related question. The Ice Barrier does not solve the ice-damming problem, it just helps to prevent damage. What if one uses raised-heel trusses such that the insulation level over the wall is at least R-30. Wouldn't this negate the need for the Ice Barrier per R104.11?

Not in my world....

 

[Sifu]

Oh boy! I just spent many days trying to catch an AHJ up on roof inspection backlogs. Several months worth. On a significant number of roofs I made this observation based on the 2018 code....very few were doing it. The problem stemmed from "bonus room" types of designs, where there was a heated wall under the slope of the roof. I was questioned about the requirement, asked WHY? Easy enough to explain how it applies, not as easy to answer why 8/12 was the driver. The only logical explanation I could come up with was that it was possible that the writer of the code determined that on an 8/12 or greater slope, in some cases, the sun never hits a given side of the the steeper slope, but on the opposite side significant melting and re-freezing could occur.

I found it odd that it was easy enough to read how to place the ice barrier 24" up the eave, but that in the same paragraph nobody seemed to be able to read past it. Even if nobody understood the requirement, I would think questions would have been asked.

I have seen ice dam damage on eaves. I don't recall ever seeing it in the middle of a roof.

 

[steveray]

I have seen ice dam damage on eaves. I don't recall ever seeing it in the middle of a roof.

We never called it there.....Just 24" inside the lower level wall line...Gets stupid with a joined front porch roof too...Tough to write a code section that accommodates all of it...

 

[Sifu]

But, I just read the 2024. It is still there. This is from the digital codes online, so is there errata?

 

[mtlogcabin]

Notice an ice barrier is not required for a metal pan roof
This is what we are typically seeing in our area since installed over the entire roof since it is also permitted as an underlayment.

or a self-adhering polymer-modified bitumen sheet shall be used in place of normal underlayment and extend from the lowest edges of all roof surfaces to a point not less than 24 inches (610 mm) inside the exterior wall line of the building.

 

[wwhitney]

I am a bit unclear on the geometry here: I understand "24 inches inside the exterior wall line of building" to refer to a dimension in plan (projection onto the horizontal plane). And the "exterior wall line" to mean the exterior face of the exterior wall, and the "eave edge" to mean the edge of the roof including any overhang.

So for the case of an 8:12 pitch roof with no overhang (eave edge = exterior wall line), every 1" in plan is 1.2" along the roof slope. That means the main requirement extends 29" along the roof slope, and the second paragraph just says to extend it 7" farther. But if you have any roof overhang, or if the slope is steeper, the effect of the second paragraph will be reduced or eliminated. E.g. for an 8:12 slope roof with a 7" or greater overhang, or for a 14:12 or greater slope roof with no overhang, the second paragraph will always be satisfied if the first paragraph is.

Is that all correct? If so, it seems like the second paragraph would rarely make any difference.

Cheers, Wayne

 

[steveray]

I am a bit unclear on the geometry here: I understand "24 inches inside the exterior wall line of building" to refer to a dimension in plan (projection onto the horizontal plane). And the "exterior wall line" to mean the exterior face of the exterior wall, and the "eave edge" to mean the edge of the roof including any overhang.

So for the case of an 8:12 pitch roof with no overhang (eave edge = exterior wall line), every 1" in plan is 1.2" along the roof slope. That means the main requirement extends 29" along the roof slope, and the second paragraph just says to extend it 7" farther. But if you have any roof overhang, or if the slope is steeper, the effect of the second paragraph will be reduced or eliminated. E.g. for an 8:12 slope roof with a 7" or greater overhang, or for a 14:12 or greater slope roof with no overhang, the second paragraph will always be satisfied if the first paragraph is.

Is that all correct? If so, it seems like the second paragraph would rarely make any difference.

Cheers, Wayne

The second paragraph relaxes the first for steeper roofs....And maxes out at 36" basically....

 

[wwhitney]

The second paragraph relaxes the first for steeper roofs....And maxes out at 36" basically....

There's no language in the second paragraph stating that it is a relaxation of the requirement in the first paragraph. So the second paragraph is simply an additional requirement. Both requirements apply; whichever requirement is stricter will control.

Cheers, Wayne


Cheers, Wayne

 

[steveray]

There's no language in the second paragraph stating that it is a relaxation of the requirement in the first paragraph. So the second paragraph is simply an additional requirement. Both requirements apply; whichever requirement is stricter will control.

Cheers, Wayne


Cheers, Wayne

It's supposed to...but like most other changes these days...Poor wording.....You should never need more I&W on a 20 pitch than a 5 pitch.....If the first paragraph governs, you do....

 

[wwhitney]

It's supposed to

Maybe (I haven't followed the code change process), but if so, the wording is incredibly dumb. All they would need to do is put "Exception:" in front of the second paragraph to make it clear it overrides the first paragraph.

Given that in the 2021 IRC the last sentence (what is the second paragraph in the 2024 IRC) included the word "also," it was clearly an additional requirement then. So anyone approaching the 2024 text with that prior knowledge is likely to read it as still an additional requirement.

Also, it doesn't make sense as a replacement for the first paragraph. If I have a 20.7:12 (60 degree) roof with an 18" (horizontal projection) overhang, then the 36" requirement from the eave edge ends at the exterior wall line. So if the second paragraph were the only requirement for steep roofs, there would be no ice and water shield required over the wall plate itself, which is presumably the most important location to provide it.

So it really only makes sense as an additional requirement, one that rarely controls.
Cheers, Wayne

 

[Sifu]

I read it as additional. Not in front of a book but I believe the code says "also". So by my interpretation....it is required to run along a rake eave, from the bottom to the top, 24" inside the heated wall on the gable end. Purpose being if there is a heated wall for any portion of that roof slope (in other words, not an unheated attic, but a room inside the thermal barrier) there would be a transition from a warm roof to a cold roof (at and below a knee wall) and an ice dam could form. Why just 24" in? Why 8/12 or greater? I guess the why is for me to determine. I don't make it up, I just try to understand it. I hope it does go away because I have had trouble making sense of it in my own head, much less explaining it to someone else. Maybe the OP was referring to the '27? Maybe the online version is a first edition, or the version he has? Maybe wishful thinking?

 

[bill1952]

A related question. The Ice Barrier does not solve the ice-damming problem, it just helps to prevent damage. What if one uses raised-heel trusses such that the insulation level over the wall is at least R-30. Wouldn't this negate the need for the Ice Barrier per R104.11?

Best solution. I have R60 on ceiling to exterior wall. No roof ice what so ever. Too bad designers and builders can't get some credit for doing better than minimum.

 

[wwhitney]

I read it as additional. Not in front of a book but I believe the code says "also".

Per codes.iccsafe.org, the word "also" is in the 2021 IRC but not in the 2024 IRC. Going back to the OP, that, along with the addition of a paragraph break, is the only change in R905.1.2 between the 2021 and 2024 IRCs. A change for clarity, not a change in meaning, so not "key."

Cheers, Wayne

 

[Sifu]

Jar, can you clarify where this potential code change is?

Some background on the situation. This AHJ does not do site inspections for roofs. So specific photos are required at mid roof showing underlayment and ice barrier (the AHJ amended to require). As I started observing the issue I brought it to the attention of the AHJ. Several installations did not show the ice barrier up the roof slope, and it is difficult to determine whether there is a heated wall, so if in doubt the observation was made. Several left no doubt. As I started fielding questions from roofers who received the comments, it became clear that this issue was a "new" one, and that it had not been observed before. This would have been a much easier situation had it been observed on site with a field inspection. They could either show there was no heated wall, or throw on a strip of barrier. But, since these are photos submitted after the roof is complete (in many cases months later), compliance becomes a lot more difficult and expensive. I again explained the code requirement to the AHJ. Yesterday (after this discussion began) I received a call from them asking for further clarification, which I gave. I would like to advise the AHJ of a potential change in the code based on the OP to give them some justification in case they decide not to enforce the current provision based on the most recently published editions implying it is not necessary. The AHJ is free to make their own decisions, but this might help them justify one.

As far as the "also" being removed in '24. It is odd. I don't see a code change proposal for the '24 IRC for this section. Was that purposeful, or an editorial revision? If editorial, who decides it is just editorial, especially if it is actually an impactful "clarification"? Does/could it mean that for roof slopes 8/12 or greater that the ONLY location is along the rake eave? If so, IMO it is not an improvement in the language, but wouldn't help the current predicament anyway.

If it is proposed change to the '27, I can't find it, but I only have group A proposals. Is there a group B yet? In any case I haven't yet located where this proposal might be, and it wouldn't have been voted on yet anyway.

Simply amazing that I was in the middle of this odd situation, with a rather obscure code, and a post shows up about it, prompting this discussion.

 

[jar546]

Jar, can you clarify where this potential code change is?

I'm wondering if they accidentally made a mistake and left out the change and there will be an errata. The only change I see is a paragraph formatting change when I look at the 2024 online.

 

[wwhitney]

I'm wondering if they accidentally made a mistake and left out the change and there will be an errata. The only change I see is a paragraph formatting change when I look at the 2024 online.

Plus the deletion of the word "also".

Cheers, Wayne

 

[Sifu]

Digging (rare slow day for me right now).

It looks like the steep roof section was added in the 2015 code as part of a much wider re-write. Here is the funny thing. I look at the code change proposal but it isn't there. But it is in (my versions) of the code. How does this happen?

2015 IRC 1st printing May 2014, 2nd printing January 2016: (highlight and underline added)


Code change from Complete Revision History to the 2015 I-codes: Successful Changes with Public Comments: 2015 IRC
This was approved as modified, no public comments altered the code change. The reason statement says it is mostly a reorganization, with two minor code changes, which are not the steep slope provisions.....because it isn't in the change proposal.

View attachment 14394

RB435-13


I would like to deal with this one issue, but it brings a larger question to mind that I have wondered about before, of which this is a great example. How some things make it into code with no apparent voter approval (and in this case, no apparent proposal). The ones I have noticed in the past are usually clearly editorial but to me, this would not be considered editorial, but if so who is deciding what is editorial?

So we have a change, not an insignificant one IMO, with no reason statement, and worse yet no actual proposal that I can find. Could it be that there was a different proposal, that wasn't moved forward and someone just decided to add it in? Is this a correlation committee thing? Should that not be identified? I checked the various documents on the ICC website for a record of this but I can't find it. If that is the case should that be happening? This isn't an old change, so there should be some history to it somewhere, right? The only place I can seem to find with a record of any change to this section is from the significant changes document I pasted.

I humbly admit I have trouble understanding how the soup is made. All the different monographs, public hearings, public comments, meetings and voting confuses me a bit, so maybe there is some history to this change I just can't find. I can't even find consistency in the different monographs for the change where this apparently occurred.

 

[bill1952]

Somewhat related, a first story porch with roof that would never be conditioned, and porch roof is flashed into vertical wall of 2 story house. Seems porch eave should be exempt like detached building.

Could make a case for ice and water at top of porch roof better than at wave. No ice dam at eave.

 

[bill1952]

Is everyone relying on the CDP documents for 2024 IRC? I'm concerned this is editorial and will be different in published version.

 

[wwhitney]

I would expect the ICC to have the correct latest version on their website.

CHAPTER 9 ROOF ASSEMBLIES - 2024 INTERNATIONAL RESIDENTIAL CODE (IRC)

ICC Digital Codes is the largest provider of model codes, custom codes and standards used worldwide to construct safe, sustainable, affordable and resilient structures.

codes.iccsafe.org

But perhaps that is asking too much. : - )

Cheers, Wayne

 

[Inspector Gadget]

A related question. The Ice Barrier does not solve the ice-damming problem, it just helps to prevent damage. What if one uses raised-heel trusses such that the insulation level over the wall is at least R-30. Wouldn't this negate the need for the Ice Barrier per R104.11?

This is an interesting argument to make. In Canadian code, the eaves protection requirement is driven by functional statements to control ice damming. Eaves protection in NBC 2015 is not required on roofs 8:12 pitch or steeper, so it seems your codes are moving in line with ours on this issue.

I've seen a massive increase in raised-hell (drop chord) trusses, which were designed explicitly to side-step the "insulation pinch" issue that causes ice damming.

I'll have to keep an eye out for asphalt-shingled raised-heel truss roof this winter to see if ice damming is a problem on them.

Notice an ice barrier is not required for a metal pan roof

Likewise.

However, our codes do not allow metal roofing to be installed on slopes < 3:12 pitch unless specifically designed by the manufacturer. I seem to recall one US code that allowed profiled metal roofing to be installed on lesser slopes as long as butyl tape sealed the seams "as per the manufacturer," so I *think* we're pretty close there.

I noted on my own house (which has a 36" overhang) that codes did not require eave protection under Canadian Code, as the "collection point" as it were was beyond the heated/wall section. My contractor installed it anyway, although the recycled tire shingle product used sheds snow almost like metal.