dshall

Attic draft stops, when and why?

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By the way Scott, you still haven't stated exactly where the inspector wants to see draftstop. Do you even know?  That is a key piece of information. In the sketch you provided I can count at least 6 different places where draftstop could potentially be required depending on the way the structure is constructed.

He wants a draft stop every ten lineal feet of mansard attic space.

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He wants a draft stop every ten lineal feet of mansard attic space.

 

So you're essentially talking about big triangular pieces of drywall, plywood, fiberglass, etc.?  

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He wants a draft stop every ten lineal feet of mansard attic space.

 

BTW, years ago when I was doing commercial  work,  this was very standard...  .  But I have not seen this requirement for residential work,  which is something Perry brought up earlier.... ,  but I cannot find this in the code book where the requirement is dependent upon whether it is commercial or residential project.

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So you're essentially talking about big triangular pieces of drywall, plywood, fiberglass, etc.?  

correct

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Your attic does not have a usable area above it so the 10' rule does not apply, but since it is within 5' of the property line the 10' rule may apply.

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Its more than I have time or energy to try and discuss in detail here right now, but read R302.11 Scott...

R302.11 Fireblocking.

In combustible construction, fireblocking shall be provided to cut off all concealed draft openings (both vertical and horizontal) and to form an effective fire barrier between stories, and between a top story and the roof space.

Fireblocking shall be provided in wood-frame construction in the following locations:

1. In concealed spaces of stud walls and partitions, including furred spaces and parallel rows of studs or staggered studs, as follows:

1.1. Vertically at the ceiling and floor levels.

1.2. Horizontally at intervals not exceeding 10 feet (3048 mm).

2. At all interconnections between concealed vertical and horizontal spaces such as occur at soffits, drop ceilings and cove ceilings.

3. In concealed spaces between stair stringers at the top and bottom of the run. Enclosed spaces under stairs shall comply with Section R302.7.

4. At openings around vents, pipes, ducts, cables and wires at ceiling and floor level, with an approved material to resist the free passage of flame and products of combustion. The material filling this annular space shall not be required to meet the ASTM E 136 requirements.

5. For the fireblocking of chimneys and fireplaces, see Section R1003.19.

6. Fireblocking of cornices of a two-family dwelling is required at the line of dwelling unit separation.

The area you're talking about could definitely qualify as concealed horizontal space that needs to be draftstopped IMO.

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......

The area you're talking about could definitely qualify as concealed horizontal space that needs to be draftstopped IMO.

 

 

 

I do not need an answer.....  unless you have a specific answer.....

 

I go back to my initial question,  what is the difference between the two attic spaces in post 13?

 

Which of the two spaces is a concealed space and what is the definition of a concealed space?

 

Which of the two spaces is a horizontal space and what is the definition of a concealed space?

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dshall, on 14 May 2016 - 10:40 AM, said:

I do not need an answer..... unless you have a specific answer.....

I go back to my initial question, what is the difference between the two attic spaces in post 13?

Which of the two spaces is a concealed space and what is the definition of a concealed space?

Which of the two spaces is a horizontal space and what is the definition of a concealed space?

"I go back to my initial question, what is the difference between the two attic spaces in post 13?"

For starters, your "mansard" roof is not above the top story. Its also concealed as opposed to many attics that have an attic access.

"Which of the two spaces is a concealed space and what is the definition of a concealed space?"

Your "mansard" roof area is a concealed space. I'm not certain of the exact definition of concealed space. I actually believe that the fireblocking section is the only place in the entire IRC that uses the term. It seems pretty clear to me though that its any space that's inaccessible and that can serve as an easy pathway to allow fire to travel from one area to another. I kinda think that any area or transition a firefighter can't easily access or visually inspect could be considered "concealed". I think you just have to use some judgement...might be the reason they left the definition a little vague and open to interpretation. This seems like a decent article on the subject though...

http://www.fireengineering.com/articles/2011/08/havel-concealed-spaces.html

"Which of the two spaces is a horizontal space..."

In this case, the triangular shaped pathway created by your "mansard" roof.

BTW, I used quotations around the word "mansard" because that particular roof isn't what I understand a mansard to be. All good. I just don't want to be the one responsible for redefining terminology (at least not in this case) : )

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Yes,  but do you have an answer to my question?

 

We are all citing passages but nobody has answered my question yet.

 

Scott - i do not think you need the draft-stops by code.  I suppose the inspector is defining the roof space as floor???  There is a good chance the inspector is making a mistake (happens all the time) but i've come to realize those fights can go bad places.

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Any concealed space with a  floor or ceiling assembly above must be have a fire separation if the area exceeds 1000 sq ft. In residential dwelling attics don't need separation. In the basement yes and you also have to do vertical firestopping between the wall and foundation every 10' OC. When it comes to Commercial. In 1 story dwelling it has to be done between roof assemblies and drop ceiling, or if there is an attics, and you got other requirements when dealing with 3 or more stories above.

 

@Ken, around here if it's 5' or less from the property line, you have to have a fire rated wall and soffit assembly, no  separation in the attic, but that would also be dependant on jurisdiction. 

post-4069-0-59435700-1463308716_thumb.jpg

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Another question: if a firestop is required, then is an access to each space also required?

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Draft-stopping and fire-stopping are slightly different things but often get confused since they are so similar. Firestopping is to actually restore fire-rating for separated spaces or prevent a fire from spreading - Draftstopping is choke a fire's air supply by making it difficult/impossible for it to pull air from an adjoining space.

I believe Scott is referring to draft-stopping, although his very first post he does say "fire block".

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