hurricane standards plus underlayment

Guest User
8/17/2004
I am receiving bids on 5 v crimp metal roofing which replaces fiberglass shingles on a 3/12 pitch roof. Current roof is 5/8 inch plywood on manufactured trusses spaced 24" on center. Per 1987 code, it was nailed down with 8 penny nails. No leaks though shingles are beginning to show wear. Main reason for replace though is to increase strenght of envelope against strong hurricane force winds. Several questions: One installer is recommending 2 layers of 30 pound felt with 15# slip sheet after re-nailing entire roof with galvanized #10 ring shank nails spaced in between old nailing pattern to trusses. Any ideas on increasing strength standards any more or better especailly after Charley??? Is it worth it to add second layer of felt for good finish???? Is 5v metal crimp same wind strength as standing seam metal roof????? House is dark brown, 2 story. Best color might be forest green, but installers say colors fade in south Florida badly. They are recommending galvalume with a clear cote finish. Thoughts on color issue??? Please focus on hurricane issues and ideas. Thank you for your comments back. Scott
Allan Reid
Dura-Loc Roofing Systems, Inc.
8/18/2004
You touch on a number of issues in todays marketplace on wind issues and misconceptions on metal roofs. Florida has a new state wide building code which has certain High Velocity Wind Areas included. All roofing products must now carry a State of Florida product approval which means it has undergone certain testsings specifically to wind driven rain, underlayment, wind uplift and fasyteners, etc. You should ensure that any product you choose carries the approval. The HVWA require impact testing for flying debris unless it is installed on min 5/8" fir plywood. The code includes minimum fastening of the plywood and if the you are in an HVWA, then the product must have been tested and the product approval report will dictate how many fasteners, type and placement in not only the plywood but the roof attachement to the plywood. The Florida Building code was based on the Southern Building code with Inclusions of the South Florida building code. I believe it requires a minimum of 30lb felt but more importantly if it is to be used in the HVWA then the roof system must have been tested for wind driven rain and as such that product approval will dictate which underlayment and how it is fastened. Strength of a panel is determined by the profile and thickness of the metal substate. The MCA recommends a minimum of G90 painted or AZ 50 bare for metalic coated steel. 5V crimp metal is a commodity product with little strength and generally needs to be laid on a solid substrate. Again check with the manufacturer for conditions and product approvals. Standing Seam also comes in many shapes and fastening. Again select one and check with the manufacturer and make sure it carries the product approvals. Colour is a big issue as thats ia all it is. You should be choosing a paint system for its properties. MCA has a certifcation program where a Premium sytstem needs to be a minimum 70% PVDF based system and a Standard is a Silicinized Modified Polyester. Both need to use ceramic pigments and come with coating warranties from the paint manufactuerer. We at Dura-loc offer both of these along with our ceramic granular finsh. If you want a dark colour make sure it is a PVDF however I would choose an Energy Star rated product to help reduce energy costs. On average 33% of a FL electrical bill is for air conditioning and a relective roof will reduce this significantly. Check out akl the reports at the DOE or Florida solar research.
Guest User
8/18/2004
Thank you for your detailed reply. A few follow ups: Is the 5 v metal crimp any stronger or weaker than standing seam for high wind value as long as it is installed per the maunfacturers' spec's? One salesman says yes and one says no??? Also, is the second layer of 30# felt worth the extra money on the 5/8" plywood or not - one salesman says it's their standard, one says unnecessary waste. Please advise back, and thanks for the prompt response.
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