Double Roofs

[conarb]

We had some firemen killed here when fighting a fire where a new higher pitched roof had been added over an old lower pitched roof, at the time there was talk of a code provision to ban this practice but I don't know if it ever made it, does anyone know?

 

[fatboy]

Only thing I can think of off the top of my head, would be the requirements of R807.1, attic access.

 

[MASSDRIVER]

I turned down 2 of those in Burlingame a few years back. The recession hit and I really, REALLY needed the money but could'nt bring myself to do it. Just seemed like nothing but problems.

Brent.

 

[conarb]

Only thing I can think of off the top of my head, would be the requirements of R807.1, attic access.

I guess it never made it into the codes, as I recall our county prohibited it after the deaths, but I don't see that prohibition anymore. Here was the case:

[QUOTE='ABC] Crews also had a hard venting the fire from the roof."The problem in that particular structure was there was an original flat roof and a pitched roof had been built on top of it. So the ventilation crew was unable to get into the area where the fire was actually was burning," said Keith Ritcher. ¹

[/QUOTE]The reason I ask is somebody in Michigan proposed doing that and I wondered if it's still legal.

¹ http://abclocal.go.com/story?section=news/local&id=6277677

 

[conarb]

What about fire stopping requirements? As I recall in the UBC we had to fire stop every 10' vertically and horizontally, didn't that make it into the I Codes?

 

[conarb]

This is a surprise to me, I was sure it made it into the codes, maybe something given up to get sprinkler approval? What about R327.5.2?

[QUOTE='2013 CRC]R327.5.2 Roof coverings. Where the roof profile allows a space between the roof covering and roof decking, the spaces shall be constructed to prevent the intrusion of flames and embers, be firestopped with approved materials or have one layer of minimum 72 pound (32.4 kg) mineral-surfaced nonperforated cap sheet complying with ASTM D 3909 installed over the combustible decking.

[/QUOTE]I know that's designed for the surface of roofs but when you have a roof over a roof wouldn't that apply?

I think it's R302.12 Draftstopping.

[QUOTE='2013 CRC]
R302.12 Draftstopping. In combustible construction where there is usable space both above and below the concealedspace of a floor/ceiling assembly, draftstops shall be installed so that the area of the concealed space does not exceed 1,000 square feet (92.9 m2). Draftstopping shall divide the concealed space into approximately equal areas. Where the assembly is enclosed by a floor membrane above and a ceiling membrane below, draftstopping shall be provided in floor/ceiling assemblies under the following circumstances:

....1. Ceiling is suspended under the floor framing.

....2. Floor framing is constructed of truss-type open-web or perforated members.

[/QUOTE]

 

[RFDACM02]

Roofs over roofs are truly a problem for firefighters trying to ventilate heat, smoke and products of combustion. We cannot cut open one hole, climb part way in and cut another, as we'd be trapped in the "Chimney" upon opening the second hole. That being said, it's rare that the codes change to specifically address firefighting efforts. Chances are where this is done, the building will suffer far greater losses and firefighters will be significantly hampered or placed in greater danger without proper ventilation. At the minimum, the FD should be made aware roof overs are being constructed so they know that on arrival.

 

[Inspector 102]

This is always a concern with roof crews doing any type of ventilation. We utilize positive pressure from the ground level and try to eliminate any crew going to the roof to cut an opening. This type of ventilation has always worked well for our community. As an inspector, I require the lower roof to be substancially removed to allow for proper ventilation of the lower attic space. Draftstopping for a single family dwelling typically would not require anything additional other than open framing members. It is tragic to hear about the death of firefighters because of these situations. I hope it never happens on my department.

 

[conarb]

This is always a concern with roof crews doing any type of ventilation. We utilize positive pressure from the ground level and try to eliminate any crew going to the roof to cut an opening. This type of ventilation has always worked well for our community. As an inspector, I require the lower roof to be substancially removed to allow for proper ventilation of the lower attic space. Draftstopping for a single family dwelling typically would not require anything additional other than open framing members. It is tragic to hear about the death of firefighters because of these situations. I hope it never happens on my department.

What code section to you cite when requiring it? Draftstopping? But draftstopping is now 1,000 square feet, dividing the areas between the roofs into 1,000 square foot segments won't do much good, but maybe just requiring it will make the contractor think twice and remove the sheathing from the lower roof since that's cheaper than draftstopping.

 

[steveray]

You could enforce "attic" access provisions, but that is probably all legally....In the IRC at least

 

[RFDACM02]

This is always a concern with roof crews doing any type of ventilation. We utilize positive pressure from the ground level and try to eliminate any crew going to the roof to cut an opening. This type of ventilation has always worked well for our community. As an inspector, I require the lower roof to be substancially removed to allow for proper ventilation of the lower attic space. Draftstopping for a single family dwelling typically would not require anything additional other than open framing members. It is tragic to hear about the death of firefighters because of these situations. I hope it never happens on my department.

Vertical ventilation is certainly a lesser used tactic in residential structures, owing to the compartmentalization which often hinders actual ventilation and more often due to understaffed FD's. Here in the NE we're not as "pro-positive pressure" as many (most homes) are temperature regulated by windows and doors, making effective PPV less efficient. Also, new evidence is showing that much ventilation is counterproductive where water isn't immediately being applied to the fire. All beyond the scope of this discussion, but the reality of "why" we have some of these regulations and how they might become less requisite in the future?