Ponding on Roof with continuous gutter

[AUGUSTACOURTER]

All of the design guides (SJI Tech Bulletin #3, etc) are written in such a way to make me think that the calculations and designs presented therein are for roofs where drainage is blocked and the rain loading is a function of the difference in secondary and primary drain elevations. In the case of a 1/8" per foot slope with a continuous gutter, do these equations/methods still apply? I understand that 1/4" slope requires no ponding checks per Code, but with an 1/8" slope, more analysis is needed...I am just not sure what analysis! Any insight would be appreciated.

 

[JLNJ]

I am not familiar with SJI Tech Bulletin #3 (I probably should be), but I believe ponding instability has to do with the deflected roof shape overcoming your 1/8" slope and drawing water into a "pond". The accumulated water in the "pond" causes more deflection, which collects more water, and so on until collapse. I believe this is different than a primary/secondary roof drain criteria.

 

[Deker]

JLNJ is correct. This article goes into some detail: Link.