Wind Mit Scenario #3 (Roof Calc)

[dquigley]

In Yorks class we were taught a slightly different way to determine the roof shape then what I was accustomed to. The difference is how the gable roof calculation is made. This exercise should expose the proper proceedure.

What is the roof shape of PLAN "A" ?
What is the roof shape of PLAN "B" ?

[dquigley]

Here is a more visable PLAN "A"

[Greg Bell]

A=Hip
B=Non-Hip

[John Shishilla]

Originally Posted by gbell

A=Hip
B=Non-Hip

same here

[William P. Campbell]

I agree with Greg's answer. Now if I could add to Dennis' senario. What if Plan A's entrance which is now clearly a gable was an overhang with a hip roof at the same roof line as the home. Then the same question with the hip extention 4' above the tie beam connection which is the half hour conversation I had yesterday with an Ins. agent. The difference was a thousand dollars a year to his client. I stated the non-hip description. ANY OTHER ROOF SHAPE OR COMBINATION INCLUDING HIP,GABLE.ETC. He felt it should be treated as a hip and not counted in the calculation. Opinions Please.

[dquigley]

Originally Posted by wcampbell2

I agree with Greg's answer. Now if I could add to Dennis' senario. What if Plan A's entrance which is now clearly a gable was an overhang with a hip roof at the same roof line as the home. Then the same question with the hip extention 4' above the tie beam connection which is the half hour conversation I had yesterday with an Ins. agent. The difference was a thousand dollars a year to his client. I stated the non-hip description. ANY OTHER ROOF SHAPE OR COMBINATION INCLUDING HIP,GABLE.ETC. He felt it should be treated as a hip and not counted in the calculation. Opinions Please.

I'm not sure I follow your scenario. When you say overhang, are you refering to it being an entry or foyer type situation? I assume the 4' above a tie beam refers to a raised roof line or raised truss bearing. If it is a raised entry that has a hip roof, the entire roof remains hip, it does not matter that there is an open area below as we are defining roof geometry. Open structures such as entries experience additional forces (positive & negative) depending on wind orientaion, but the roof geometry stays the same. You should not designate a roof as something other than a hip simply because it is raised, or open space below. I am leaning towards the same answer as your insurance agent, but i may be misunderstanding your question --- please elaborate a little more.

[dquigley]

I'm going to continue adding to this basic roof geometry -- maybe a second floor and some flat areas so that we can beat this thing to death. It will have its own wind mit Scenario # ----- Roof geometry calcuations as taught by York are quite different from the way I was doing them in the past, so I think we should continue to review this subject -- Do you readers want to continue with roof geometry?

[John Shishilla]

Originally Posted by dquigley

I'm going to continue adding to this basic roof geometry -- maybe a second floor and some flat areas so that we can beat this thing to death. It will have its own wind mit Scenario # ----- Roof geometry calcuations as taught by York are quite different from the way I was doing them in the past, so I think we should continue to review this subject -- Do you readers want to continue with roof geometry?

Are you trying to scare us?

Bring it!

[dquigley]

Fear is in the eye of the beholder -- lol

[William P. Campbell]

Dennis, I will install a picture to clarify my senario.

[William P. Campbell]

I got the picture up. It is that front entrance that I was to understand should be included in my non-hip calculation along with a gable in the back of the home. That front area puts it over the 10% mark.

[John Shishilla]

If I understand correctly;

I include these sides in the calculations, I add fascias and gable bottom cords. If there is two stories, it could be a bit different.

[William P. Campbell]

John, my question is should this entrance roof structure be part of the non-hip calculation added to the gable in the back of the house. If so it would push it over the 10% mark.

[John Shishilla]

Originally Posted by wcampbell2

John, my question is should this entrance roof structure be part of the non-hip calculation added to the gable in the back of the house. If so it would push it over the 10% mark.

The entry roof is all hip and it should be used in the calculations.

[dquigley]

Originally Posted by wcampbell2

John, my question is should this entrance roof structure be part of the non-hip calculation added to the gable in the back of the house. If so it would push it over the 10% mark.

It should be used in the calculation, but used as a hip roof, not as a non hip roof. When calculating the lineal footage of roof across the entry, only count the width of the raised entry once, do not add additionaly for the house roof across this opening.

I believe your main hang up is in classifying the entry roof type. It is a hip roof, not a gable. A gable roof has a flat face forming a trianglular wall, all you have here are sidewalls underneath a hip roof.

Take the horizontal measurement of the gable roof in the back and devide by the total roof fascia measurement (which includes the front entry lineal footage). If it is less than 10%, the roof is classified as hip. I'm pretty sure you have a hip classification.