Ridge supported by a wall or girder.

[Jobsaver]

I am wanting to get some feedback on the following code section. Still on the 2006 IRC.

R802.3.1 Ceiling joist and rafter connections. (midway through code section)

Where ceiling joists or rafter ties are not provided, the ridge formed by these rafters shall be supported by a wall or girder designed in accordance with accepted engineering practice.

 

[mjesse]

Something is required to keep the walls from bowing out - Articles-3

Be it CJ's, CT's, or a wall/girder

mj

 

[steveray]

Not getting where you are going....if there is not a "rigid triangle" the ridge gets supported by a beam or wall.....I think that is my simplest explanation...

 

[Yankee]

Something is required to keep the walls from bowing out - Articles-3Be it CJ's, CT's, or a wall/girder

mj

I am not at all fond of that handout as it (imho) incorrectly discusses Collar ties as used in common dimensional framing. This handout appears to be discussing timber frame which has different properties.

 

[mjesse]

I am not at all fond of that handout as it (imho) incorrectly discusses Collar ties as used in common dimensional framing. This handout appears to be discussing timber frame which has different properties.

Agreed. I intended to just link a photo illustrating the forces present, my bad.

My point remains though, if no cj's or ct's, beam/wall/girder required.

mj

 

[mark handler]

The intent of Section R802.3.1 is to provide for a structural ridge when ceiling joists or rafter ties are omitted. When the ceiling joists or rafter ties are present, but have been raised above the top plate, one must apply the rafter span adjustment factor, but one need not provide a structural ridge in addition

 

[Jobsaver]

I remember on a different thread a few months back where fatboy suggested that a properly supported or braced ridge will in itself negate the requirement for parallel ceiling joists (tied to rafters), or rafter ties, because spreading becomes impossible if the ridge can't drop. It appears to me that the intent of 802.3.1 supports this idea. However, I am reading into this that the support structure must be designed by a designed professional?

 

[markw]

R106 Code Commentary-The code is prescriptive and makes possible the

design of a dwelling or townhouse without the requirement

for a licensed design professional. However, the

construction documents must be prepared by a

licensed design professional when required by the

statutes of the state or jurisdiction. Additionally, the

building official has the authority to require that plans

be prepared by licensed design professionals when

not otherwise required by the statutes of the jurisdiction

if, in the opinion of the building official, special or

unique conditions exist or if the design of a building

does not meet the prescriptive provisions of the code.

 

[fatboy]

What I was saying is I don't feel you have to be a DP to calculate a simple span beam, that could support the rafter without the use of ties. There were those that disagreed with me, which is their right. I didn't change their mind, they didn't change mine.

 

[Jobsaver]

What I was saying is I don't feel you have to be a DP to calculate a simple span beam, that could support the rafter without the use of ties. There were those that disagreed with me, which is their right. I didn't change their mind, they didn't change mine.

I do a lot of residential inspections, and am comfortable relaxing on the rafter tie criteria where a ridge is well braced to walls or beams below. When reviewing this topic this morning, R802.3.1 just kind of jumped off the page, and I had not previously considered the merits of the portion of this code section cited above. I am not a design professional, but know a well supported ridge when I see one, and totally agree with the logic that if the ridge can't fall, the walls can't spread. Guess I'm looking for a bit of assurance that I am operating within the intent of this code section.

 

[Yankee]

I do a lot of residential inspections, and am comfortable relaxing on the rafter tie criteria where a ridge is well braced to walls or beams below. When reviewing this topic this morning, R802.3.1 just kind of jumped off the page, and I had not previously considered the merits of the portion of this code section cited above. I am not a design professional, but know a well supported ridge when I see one, and totally agree with the logic that if the ridge can't fall, the walls can't spread. Guess I'm looking for a bit of assurance that I am operating within the intent of this code section.

I agree and I think that is why that section cites a beam OR WALL supporting the ridge. In the old days it was commonly the center bearing wall that supported the ridge (and center bearing wall that supported the centerline all the way down through the building. So it doesn't have to be a beam, it can be a supporting system such as a wall.

 

[GBrackins]

What I was saying is I don't feel you have to be a DP to calculate a simple span beam, that could support the rafter without the use of ties. There were those that disagreed with me, which is their right. I didn't change their mind, they didn't change mine.

I agree Fatboy,

ridge beams and ridge connections can be prescriptively designed by following:

1. Table 3.29 (A-D) of the Wood Frame Construction Manual for sizing of ridge beams based upon ground snow load

2. Table 3.6 & 3.6A for ridge connection

 

[markw]

Is it weird that I keep coming back to read this stuff-my family thinks so....