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Flat roofs in coastal areas

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I have a project on the South Carolina coast that will have a flat roof.  The design wind speed is 130 mph resulting in a wind load of 44 psf uplift.  The roof has a standing seam roof with cold-formed metal framing cornice around the perimeter of the building so the flat portion of the roof is somewhat sheltered.  Below is my first attempt at test graphics to describe the roof.


        /|                                   |\
       / | Cornice                           | \   Cornice
      /  | framing                           |  \  framing
     /   |                                   |   \
    /    |                                   |    \
   /     |              flat roof            |     \
   -------------------------------------------------
  ||                                               ||
  ||                                               ||
  ||                                               ||

I have two questions (so far) regarding this roof.
1.  Could the actual uplift pressure on the roof be higher than the standard flat roof wind load due to the cornice roof?

2.  The roofing is to be a gravel ballasted built-up roof.  Does the weight of the ballast need to offset the wind uplift?  If not, what is the mechanism that holds the roofing down?

Thanks in advance,

Warren S. Foy, P.E.
Structural Design Manager
The Mason & Hanger Group Inc.



300 West Vine Street, Suite 1300
Lexington, KY 40507-1814
v 859.252.9980 x221
fax: 859.389.8870
web: http://www.mhgrp.com 

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