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Ask-The-Experts > Installation

Florida building code help
we currently have an old 3 tab shingle roof.  It is not leaking but is 24 years old.  I am looking at installing a metal roof over our current shingles.  my preference would be to install them over an underlayment directly over the shingles with out battens. I know it's best to remove the old shingles but I'm doing this by myself. having the shingles on allows me to work at the pace I would be able to do.

the issue is that I have been trying to find what current building code is without much luck.  I went to my local code office, and got some printouts of local code but we were pretty sure I could do it myself but we stilll had some doubts. Where we live there arent a lot of diy people around especially for roofing. So I think I'm the first.

after I showed him some papers and work I have found he said he would issue me a permit.  is he the only person I have to have sign off on this or are there others. 

The code I showed him was section 611 re roofing of the 2010 florida building code - existing building. 

It states  611.3 recovering versus replacement

new roof covering shall not be installed without first removing all existing layers of roof covering where any of the following conditions occur:

1. Where the existing roof is water soaked or deteriorated and unsuitable as a base for additional roofing

My roof is dry and the wood in good condition.

2 is the existing roof is wood shake, slate, clay, or asbestos tile

None of these apply to my roof

3 where the existing roof has 2 or more layers of roofing

Doesnt apply to my roof

4 where blisters exist if they do exist they must be cut and scrape down

No blisters on my roof

5 where the existing roof is to be used for attachment for a new roof system and compliance with the securement provisions of section 1504.1 can not be met.

Im not using my existing shingles as the foundation to what I attach the metal to.

my thinking correct or have I missed something. I just want to make sure that I'm going to get done with my roof and then it be uninsurable or something. Thanks so much.
This all sounds logical and well thought out. As far as other signatures, I really am not sure. A lot will have to do with the product you're installing. If it has Florida approval for your region, then there is a chance that nothing else is needed. Otherwise, you may need to get an engineer involved. I suggest choosing your product and manufacturer and then working with them to help figure out what all is needed, as well as with your local building inspector.
Casey,
You are looking at the right section of the code. This same requirement in in the 2010 FBC, section 1510.

The key thing is to make sure the sheathing (plywood / OSB) has not deteriorated. If you plan to leave the shingles on, then as a minimum I would recommend inspecting the sheathing from the attic. If the sheathing is not accessible form the attic, then I would periodically cut through the shingles to inspect, including valleys.

Another recommnedation is to cover the shingles with an underlayment such as 30# felt or a synthetic.This will tend to seperate the shingle granules from the metal roof during installation (granules can get stuck on shoes and scratch the paint) and during the life of the roof (as the panels expand and contract with temperature change, the granules could scratch the back side of the panels).

As far as next steps, you could select a manufacturer. Serveral MRA members have products approved by the Florida Building Commission. You can search their web site at www.floridabuilding.org/pr/pr_app_srch.aspx. This would allow you to select a product. Most manufacturers can provide engineering support to demonstrate the approved products meet the code's load requirements for your application.

Good Luck,
David Stermer
thanks so much for the help.  that really eases my mind so I can get started on this job.  I have inspected all the plywood from the attic and there is 1 piece of that I would like to replace. 

the next question is  how do I need to replace that 4 by 8 sheet of plywood.  what I mean is after I'm all finished replacing the plywood do I have to install shingles again to make that section level with the rest of the roof before I apply the metal?

by the way the plan is cover the shingles with a synthetic underlayment then to install grand rib with 1 and a half inch screws in the flats of the panels.  Not sure on spacing of screws yet.

By the way does anyone have any recommendations on what type of underlayment to purchase thats affordable?  Is it that much better and more expensive than 30lb felt.  Can I even use 30lb felt under code?
Casey,
It is important that the roof surface have a consistent plane. Areas that sag or are otherwise out of plane need to be brought in plane. Shims are commonly used. Installing shingles on the 4x8 replaced plywood is also a good way to bring that area of the roof surface in plane.

Synthetics work well, I prefer themn over 30# felt. Section 1507.4.5 of the Florida Building Code states "Underlayment shall be installed as per manufacturer's installation guidelines". So get with your manufacturer to see what they recommend.

Regards,
David Stermer

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