When you are considering re-roofing a residential or a commercial building there are many criteria that should be considered before proceeding. Most importantly, unless the new system replicates and replaces the old and there is no existing structural damage, you may need to engage a structural engineer.

Obviously an engineer is required when determining whether the structure is competent to support a change and/or increase in loads. This condition is discussed within both the Florida Building Code (FBC) and the Florida Existing Building Code (FEBC):

FBC 1510.2 & FEBC 511.2 - Structural and construction loads Structural roof components shall be capable of supporting the roof-covering system and the material and equipment loads that will be encountered during installation of the system.

The need for an engineer is less obvious when a roof contains structural damage or when upgrades to roof strapping are required. Structural damage is discussed within the Florida Existing Building Code, but upgrade requirements are discussed outside of the building code, in §553.844, Florida Statutes:

FEBC 407.3.4 - Other uncovered structural elements Where in the course of conducting repairs other uncovered structural elements are found to be unsound or otherwise structurally deficient, such elements shall be made to conform to the requirements of Section 407.3.2.1.1.

With this less obvious condition the following ‘triggers’ can be used as guideline for when to seek the expertise of a structural engineer:

• The current system is to be replaced by a heavier system, i.e. shingles to tile.
• The new membrane/system will be installed atop the old.
• The work includes the addition of rooftop equipment.
• The current system has a history of drainage issues, continuous ponding of water atop the roof or a history of water intrusion.
• Uncertainty of roof continuity or hurricane ties/connections.

So if you are upgrading your roof structure or repairing/addressing and old problematic roof, you will most likely benefit by having the project evaluated by a structural engineer. If you are considering a re-roof, or would like additional information on roofing code provisions, our building envelope group is ready to assist you. Please contact Gary Pailthorp at gpailthorp@brackenengineering.com.

Code references in this article include:

FBC 1510.2 & FEBC 511.2 - Structural and construction loads Structural roof components shall be capable of supporting the roof-covering system and the material and equipment loads that will be encountered during installation of the system.

FEBC 407.3.2 - Substantial structural damage Buildings that have sustained substantial structural damage shall comply with this section. 407.3.2.1 - Engineering evaluation and analysis An engineering evaluation and analysis that establishes the structural adequacy of the damaged buildings shall be prepared by a Florida-registered engineer or architect and submitted to the building official. The evaluation and analysis may assume that all undamaged structural elements and systems have their original strength and stiffness. 407.3.2.1.1 - Extent of repair After the building is repaired the evaluation and analysis shall demonstrate that the building, once repaired, complies with the wind provisions of the Florida Building Code, Building .

FEBC 407.3.3 - Below substantial structural damage Repairs to buildings damaged to a level below the substantial structural damage level as defined in Section 202 shall be allowed to be made with the materials, methods, and strengths in existence prior to the damage unless such existing conditions are dangerous as defined in Chapter 2 . New structural frame members as defined in Chapter 2 shall comply with Section 407.3.1.

FEBC 407.3.4 - Other uncovered structural elements Where in the course of conducting repairs other uncovered structural elements are found to be unsound or otherwise structurally deficient, such elements shall be made to conform to the requirements of Section 407.3.2.1.1.

FEBC 507.2.1 - Replacement of Roofing or equipment Where Replacement of roofing or equipment results in additional dead loads, structural components supporting such reroofing or equipment shall comply with the vertical load requirements of the Florida Building Code, Building. Exceptions: Structural elements whose stress is not increased by more than 5 percent. Buildings constructed in accordance with the conventional construction methods of the Florida Building Code , Building and where the additional dead load from the equipment is not increased by more than 5 percent.

§553.844, Florida Statutes - "Hurricane Mitigation Retrofits for Existing Site-Built Single Family Residential Structures" (for more information, see the article titled, "Code Updates: Newly Passed Roofing and Storm Shutter Requirements" published in Bracken Engineering eNewsletter, Volume 1, Issue 4.)

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