Roof Replacement - 25% Rule

A roof repair, recovering, or replacement usually becomes necessary at intervals throughout the life of a structure. The word 'roof' in this context refers to the waterproofing assembly (asphalt shingles, metal panels, etc.) that is applied to the structural roof sheathing. The need for roof work may arise due to one or a combination of several factors. These include damage from hail, wind, or other relatively severe weather effects; long term deterioration from normal exposure; and accelerated deterioration or leaks due to improper original installation. The 25% roof replacement rule applies to the repair, replacement, or recovering of existing roofs throughout the State of Florida. The rule states the following:

“Not more than 25% of the total roof area or roof section of any existing building or structure shall be repaired, replaced or recovered in any 12 month period unless the entire roofing system or roof section conforms to requirements of this code.”

Stated another way, the rule effectively prevents partial roof repairs, replacements, or recoverings (affecting more than 25% but less than 100%) of any individual roof section (that does not conform to current code) in any one year period.  It mandates that if more than 25% of a non-conforming roof section is to be repaired, replaced, or recovered, the entire affected roof section must be repaired, replaced, or recovered to meet current code requirements. An important aspect of the 25% rule is that it is applied to individual roof sections.  This allows separate roof sections to be repaired, replaced, or recovered without having to replace all the roof sections over a home or other building.  Many single family homes have only one roof section, while others have several.  The term 'roof section' is defined in the Florida Building Code (FBC), Residential and in Chapter 2 of the FBC, Existing Building as follows:

“A separating or division of a roof area by existing expansion joints, parapet walls, flashing (excluding valley), difference of elevation (excluding hips and ridges), roof type or legal description; not including the roof area required for a proper tie-off with an existing system.”

With most single family homes, separations or divisions of the roof created by expansion joints or differing legal descriptions do not exist.  Roof expansion joints are usually found only at large commercial buildings. Differing legal descriptions may occur with multi-family structures such as townhomes.  Parapet walls, roof types, and differences of elevation are commonly found with single family homes, and these result in multiple roof sections which are further explained with schematics here. The 25% rule did not always exist in the FBC, such as during the effective period of the 2001 FBC.  On October 1, 2005 the 2001 FBC was replaced by the 2004 FBC.  The 2004 FBC did not initially have a 25% rule for roofing; however, the 2005 Supplements to the 2004 FBC contained a 25% rule that was applicable only in the High Velocity Hurricane Zone (HVHZ), which is Miami-Dade and Broward Counties. The 25% rule came into effect throughout the rest of the State of Florida in December 2006, when the 2006 Supplements to the 2004 FBC came into effect.  The 2006 Supplements include a 25% rule for roofing in chapter 5 of the FBC, Existing Building that is now in effect throughout the entire State of Florida.  On March 1, 2009 the 2007 FBC replaced the 2004 FBC.  The 2007 FBC, Existing Building maintained the 25% rule in Paragraph 611.1.1.  On March 15, 2012 the 2010 FBC came into effect, and the 25% rule is maintained in the same paragraph. While not a part of the 25% rule, another FBC, Existing Building provision applicable to roof replacement is Paragraph 606.3.2:  "Where roofing materials are removed from more than 50 percent of the roof diaphragm of a building or section of a building where the basic wind speed is greater than 115 mph or in a special wind region...roof diaphragms and connections that are part of the main wind-force resisting system shall be evaluated...if diaphragms and connections in their current condition do not comply...they shall be replaced or strengthened..." This means that renailing of roof sheathing is often required as part of a roof replacement, particularly with older homes.