Combustible projections - NBC 9.10.15.5(5)

[Inspector Gadget]

Interesting question for the Canucks in the audience:

Our office has an application to replace a deck on a home built ridiculously close to a property line (in the olde days when block fires were a thing).
The deck is going to project from the rear of a house, parallel to the a property line, and 30cm (1ft) from it. It will serve the second storey of the building.
Proposed deck in yellow:




We're running into a question about the language of "combustible projections" under NBC 9.10.15.5(5):



Normally, spatial separation Code is utterly independent of what lies beyond the property line. In this case, there's a question as to whether the phrase "and that could expose an adjacent building to fire spread" would mean that combustible projections are acceptable if there's nothing on the other side. This seems counter to the spirit of spatial separation as applied elsewhere.

In any event, there *is* an adjacent building, so we're probably going to nix this, but I thought I'd reach out to generate some discussion/common ground.

 

[tmurray]

This clause is intended to deal with any projections that are not otherwise regulated in the traditionally sense when it comes to spatial separation. The highlighted clause is intended to bring context to the requirement and enable a designer to make an argument if there is legitimate reason to believe that there is no possibility now or in the future that the construction could expose an adjacent building to the spread of fire.

 

[Plumb-bob]

Are you considering that the deck may be protected as existing nonconforming? If they are rebuilding the deck exactly as it was, and they are not increasing the nonconformity, they may be protected.

 

[Inspector Gadget]

This clause is intended to deal with any projections that are not otherwise regulated in the traditionally sense when it comes to spatial separation. The highlighted clause is intended to bring context to the requirement and enable a designer to make an argument if there is legitimate reason to believe that there is no possibility now or in the future that the construction could expose an adjacent building to the spread of fire.

'Tis what I figured.

Are you considering that the deck may be protected as existing nonconforming? If they are rebuilding the deck exactly as it was, and they are not increasing the nonconformity, they may be protected.

That's an argument that's been accepted from a zoning and land-use point of view already, but we .... are a different beast. Your point lies at the crux of A.1.1.1.1(1), which I've described as one page of guidance that can be summarized "don't be a jackwagon." Old stairs from the 1800s? If you've got to hack through a beam to create head space replacing those stairs, do the best you can, right?

At the same point, A.1.1.1.1(1) and its referenced documents make it pretty clear that if we can upgrade a building and improve life safety without being onerous, we should. Replacing a non-egress window in a bedroom? Make it egress unless you can show me that it simply can't happen. (BTW: No-one has been able to do so.) We have a request in from a commercial building *very* close to a property line (as in, less than a metre). They want to re-side their building. There is no way in heck that I'd let them replace vinyl with vinyl due to spatial separation. Fire safety, and all that.

A huge part of what we are facing is code application in areas where the building inspector might have been the town clerk, public works dude, or the CAO - none of whom had a clue about codes. Hence, what is "non-conforming" in so many cases wasn't Code-compliant when it was built 40 years ago.... and I am accepting a fair bit of liability if I allow the client a "fruit of the poisoned tree" argument.

 

[Plumb-bob]

I also put up my post as conversation starter.

I think I agree with your viewpoint for this particular situation, as far as I understand it, and I would pursue the same course of action. If they are pulling a permit, it has to be to current code.

Are you going to deny the permit outright, or require noncombustible construction, or?

We have run into situations where our lawyers have told us we have no authority to enforce a change on an existing property, if a structure was built before the municipality had a building or zoning bylaw. For example, there is a property that was annexed into the municipality 40+ years ago from the regional district, which at the time had no building regulations. The multiple "houses" are a hot mess, but we are told we have limited authority to clean up the situation. We are still pursuing this, and the outcome is TBD.

Our municipality is probably several hundred years younger than yours though.

As far as A 1.1.1.1(1) goes, this is a very interesting article that I have seen interpreted very differently by different AHJs.

 

[Inspector Gadget]

Are you going to deny the permit outright, or require noncombustible construction, or?

There are several options:

1) Design the deck so the deck is 1.21m from the property line;
2) Design the deck so the elements that are within 1.2m from the property line are non-combustible.
3) Design the deck with a closed-in wall adjacent to the property line, constructed per the requirement for buildings under 9.10.15 (Ie: n/c or metal cladding over exterior-rated gypsum, to the underside of the deck - treating the deck as a roof space for interpreting 9.10.15(5)(2)
4) Fugeddaboutit.

We have run into situations where our lawyers have told us we have no authority to enforce a change on an existing property, if a structure was built before the municipality had a building or zoning bylaw.

We can't go back in to retroactively apply Codes, but our regulations are fairly clear: alteration of a building requires a permit; and work done under a permit must meet Code. Here's where A 1.1.1.1(1) comes into play. And on that note:

As far as A 1.1.1.1(1) goes, this is a very interesting article that I have seen interpreted very differently by different AHJs.

There are documents out there - NRC guides. Although they're ancient (1990 for application of Part 3 to existing buildings; 1995 for part 9), they still have some merit.

Renos/alterations of existing buildings is the most challenging "grey area" subject to interpretation.

 

[Sifu]

Not sure if any additional conclusions have been reached since this thread:

Thread 'Fire Separation Distance for Decks'

May 28, 2014

I've always had to teach this subject based on hypothetical judgement, as the IRC does not provide clear guidance about fire separation distance for decks. For the first time in ten years in my jurisdiction, I'm faced with a proposed side-yard deck in a new development where the planning/zoning division will allow a deck over 30" to be built right to the property line. Usually the setback is 5 feet, so I have never had to face this question other than hypothetically.

I know what the IRC says, but not what my code peers have done in real world application.

How do you handle FSD for...

• Glenn
• Replies: 34
• Forum: Residential Building Codes

This has ben a topic for a long time without definitive guidance other than a 2003 ICC interp (below). I am still conflicted. Glenn Mathewson included a section in his book Deck Construction based on the 2021 International Residential Code. The opinion expressed is that a deck is not a projection in the same sense that a wall, eave, or roof would be. Still the footnote allowing 0-hr for eaves without vents could be construed to imply that a deck without openings could fit there. Also note the interp says that a deck "attached" to a building. So a free-standing deck would not be a projection according to the interp. If I over-critically think that out as purposeful language, then I guess they consider the deck as not a hazard regarding projections since it's collapse would not affect the building??



So based on the ICC, it is a projection. Based on Glenn's logic it is not, however being a second story I think the logic may be less clear since it is more likely that it could be exposed to fire from below.

I have worked in many AHJ's, none have pushed the issue too hard. I remember one I did similar to your situation that gave me heartburn and I think we allowed them to protect the walls adjacent to the deck with the logic that the building would be protected. Your code uses the term building, which I assume is a defined term and the definition would matter.

 

[Inspector Gadget]

I have worked in many AHJ's, none have pushed the issue too hard. I remember one I did similar to your situation that gave me heartburn and I think we allowed them to protect the walls adjacent to the deck with the logic that the building would be protected. Your code uses the term building, which I assume is a defined term and the definition would matter.

So from those definitions our Code considers a deck a building, as it is supporting persons. Now, we're reasonable folks (don't tell, it will ruin our reputation) and try not to be too onerous on these things for residential decks. Our regulations exempt detached accessory buildings <592ft2 from building code, so if a client wants to build a 10x20 deck at the back of their minihome that's detached from the main structure and supported on deck blocks - we're not involved.

In this case, because the deck is attached, it must meet Code. It's dang (dang) close to the property line. It clearly falls within the realm of something that should be regulated. So, like a good Canadian, I will regulate it.

I've seen some of the discussions regarding the U.S. comparatives to our Spatial Separation codes but since it's apparently quite different from ours, I haven't cared to follow deeply. That said, I only just thought to ask: what's the intent of the relevant IBC/ICC codes - protect the building on the subject property, or protect what is or may be on the *adjacent* property? Canadian codes are designed to limit propagation of fire to the adjacent property (or adjacent buildings on the same property.)

 

[Plumb-bob]

Spatial separation has been the bane of my professional career so far.

Fire department response time was never considered by previous inspectors, it seems like nobody wanted to rock the boat. I took it upon myself to have response time assessed, and we indeed fall below the required threshold. Enforcing this created many hard feelings in the development community.

I try to explain to people that approximately 100 years ago our community burned down from one end to the other from a fire that started in a single building, and that this type of thing is now almost unthinkable because of modern codes.

 

[Sifu]

Spatial separation has been the bane of my professional career so far.

Fire department response time was never considered by previous inspectors, it seems like nobody wanted to rock the boat. I took it upon myself to have response time assessed, and we indeed fall below the required threshold. Enforcing this created many hard feelings in the development community.

I try to explain to people that approximately 100 years ago our community burned down from one end to the other from a fire that started in a single building, and that this type of thing is now almost unthinkable because of modern codes.

We had a fire in our area not long ago. It destroyed over 1,000 homes. The fire was driven by high winds and jumped from house to house in densely packed subdivisions. "Typical" modern codes were in place, though I am not sure many had implemented a wildland fire code. It is thinkable.

 

[Plumb-bob]

We had a fire in our area not long ago. It destroyed over 1,000 homes. The fire was driven by high winds and jumped from house to house in densely packed subdivisions. "Typical" modern codes were in place, though I am not sure many had implemented a wildland fire code. It is thinkable.

Well that is interesting. We have certainly lost entire communities to wildfires, but I cannot think of events like you say of that scale in Canada in recent memory.

The community of Lytton was lost to wildfire in 2021, and I hear they are building back with very serious fire protection measures. I wonder if this will become the norm, dictated by insurance, codes or other means.

FYI, Lytton was the hottest place on earth around the time of the fire with temps of 50C (122F).

 

[Inspector Gadget]

Fire department response time was never considered by previous inspectors, it seems like nobody wanted to rock the boat. I took it upon myself to have response time assessed, and we indeed fall below the required threshold. Enforcing this created many hard feelings in the development community.

I try to explain to people that approximately 100 years ago our community burned down from one end to the other from a fire that started in a single building, and that this type of thing is now almost unthinkable because of modern codes.

Distance between the two buildings: 10.2 metres. These were trailers on the same property, outside a 10-minute response area, but not remarkably distant from the nearest fire department.

FYI, I despise vinyl siding. It's like wrapping your house in lighter fluid.

 

[Plumb-bob]

Dont get me started with mobiles and mobile home parks. We have a park in town where (again) I am the first inspector in generations to enforce spatial separation. Added to this, the park butts up to a beautiful mature forest of spruce and pine, its a wildfire disaster waiting to happen.

We have had multiple fire in this park in the last 5 years, including a fatality. These things are designed to burn.