HomeMy WebLinkAboutEngineering FILE COPY
TURQUOISE Engineering, LLfEIVED APR 22 2015
Structural Engineering, Design & Testing, CA#28948, NOA #13-0222.02
6915 Washington Rd,W Palm Beach, FL 33405/Ph. (561)804-9908/Fax(561)804-9907/e-mail:turginc@aol.com
April 21, 2015
TO: St Lucie County / Building Department
FROM: Riza N. ALTAN, P.E.
SUBJECT: Low-Sloped Roof Uplift Pressures & Base Sheet Enhanced Fastening
ADDRESS: LARRES Residence / 115 SE Serenata Ct., Pt. St. Lucie FL 34983
CONTRACTOR: Larry NEESE, LLC
Dear Sir;
The re-roofing specifications of low-sloped roof area of the subject residential building
are reviewed by myself. The purpose of this letter is to determine the wind uplift
pressures and enhanced spacing of mechanical fasteners.
The one-story building is located in Exposure C area. The low-sloped roof measures
58'x34' and consist of 5/8" CDX plywood with positive drainage. The roof mean height
is 15 ft.
As per 2010 Florida Bldg. Code, ASCE 7-10, for Risk Category II, 170 MPH ultimate wind
velocity in Exposure C area, using Wind Load Factor of 0.6 for ASD; the wind pressures
are determined as follows:
Field: Pi _ - 44 psf/ Perimeter (4' wide): P2 = - 74 psf/ Corner (4'x4'): P3 = -111 psf
The proposed CertainTeed Modified Bitumen Roof System over Wood Decks
(NOA#14-0224.03) consists of mechanically attached 75-lbs GlasBase base sheet followed
by torched down FlintLastic GTA modified bitumen cap sheet.
The system max. design pressure of -52.5 psf [Deck 1I, Syst.E(1), page 12/16, Limitation #71
is specified by tin-tagging the base sheet with 11 ga., 1'/4" long ring-shanked roofing
nails, spaced at 8"o.c. along the laps and 8"o.c., three rows staggered in mid-sheet.
It is required that, as per RAS 117 in order to meet the actual roof pressures, the base
sheet is tin-tagged to the existing 5/8" plywood deck in the following enhanced pattern:
Zone 1: Field (Intermediate areas): @ 8" o.c., staggered three rows in mid-sheet,
Zone 2: Perimeter (4' from edges): @ 4" o.c., staggered three rows in mid-sheet,
Zone 3: Corner (4' from ea. side): @ 4" o.c., staggered four rows in mid-sheet.
Laps: Field areas @ 8" o.c., Perimeter @ 4" o.c., Corners @ 4"o.c.
Therefore, this letter is to certify that installation of CertainTeed Modified Bitumen Roof
System (NOA #14-0224.03) torched-down re-roofing system conforms to requirements of
2010 Florida Building Code which specifies 170 MPH ultimate wind speed for Risk
Category II in Exposure C area.
If you have any questions regarding this matter or I maKKI���9��tAfor,,assistance, please
do not hesitate to call me. ,e �'I,P' S. AjTq�y�6d�
Sincerely, .
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Riza N. ALTAN, P.E. 38521 STATEOF
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