Georgia Residential Roof Building Codes

The state of Georgia splits the responsibility with local jurisdictions for enacting and enforcing the state's residential building codes. The state legislature enacts the laws, but leaves regulation up to counties and cities. Like most states, Georgia has adopted a model building code, termed the International Residential Code. This model code sets out minimum standards for roof structures and other aspects of residential construction in Georgia.

Code officials around the world saw the need for a model, modern code for residential buildings. To meet that need, the International Residential Code (IRC) was drafted and published by the International Code Council. It addresses the design and construction of one- and two-family dwellings and townhouses of three stories or less. It has been adopted by 49 states, the District of Columbia, Guam, Puerto Rico and the U.S. Virgin Islands. Georgia is one of the many states that uses the model IRC code as their building code.

The IRC covers roof construction, but that is not all. Its intent is to cover all aspects of construction in a single source. The IRC model code includes construction codes in general, plumbing codes, mechanical codes, electric codes and energy conservation codes. It is updated annually, and state codes enacting it are also amended yearly.

Georgia's Uniform Codes Act enacted the state building codes, found at Chapter 2 of Title 8, Section 8-2-20(9)(B). They reflect the same codes as those included in the International Building Code, which serve as the base building code. However, they have been slightly modified by a set of Georgia amendments.

Some of these Georgia codes are mandatory and some are permissive. The mandatory codes apply across the board to all construction in the state, whether or not the counties and cities decide to enforce them. Permissive codes apply only in those areas of the state where the local government chooses to adopt and enforce them.

Both the International Building Code and the International Residential Code for One- and Two-Family Dwellings are mandatory codes in Georgia. That means that residential roofing laws, as well as fire, plumbing, mechanical, gas, electrical, energy and swimming pool codes, apply to every structure built in Georgia.

In general, the IRC sets roofing standards in several areas, including residential roofing materials, residential roof structure, residential roof ventilation and residential roof flashing and counter flashing. Georgia codes also set some regulations for re-roofing, the process of placing new roofing materials over old roofing materials.

A new roof is only as sound as the materials used. However, Georgia codes do not regulate the quality or type of materials used, and homeowners in Georgia can choose shingles, wood shakes or asphalt roll roofing, among others. The state building codes simply require that the roofing materials selected must be compatible with each other, as well as compatible with the building.

In addition, Georgia's IRC codes mandate that when a vendor delivers materials, it must deliver them in packaging that is marked with the name or other identifying information about the manufacturer. The packaging must also have the label of an accredited testing agency. What about roofing materials delivered in bulk? In Georgia, these must be accompanied by a bill of lading or a certificate containing information identifying the manufacturer and the testing agency.

The roof on a residential property is intended to protect the structure from weather conditions including rain and wind. To meet that end, the IRC requires that roofs in Georgia houses must slope. The minimum amount of slope is set out in the IRC as 2%, which comes out to ¼-inch per 12 inches. Note that this applies to new roofs only.

In addition, any deck that is built on a roof in Georgia must have a roof covering that is secured to the building with secure fasteners. Both the covering and the fasteners must be among those approved by the IRC. Any parapet walls must be covered with approved coping materials that are made of noncombustible material. The wall coping must be at least as thick as the parapet wall on which it is used.

Ventilation is important in roof construction. While well-constructed roofs will keep water out and stand up to winter winds, it is essential to protect the inside of the roof as well. That's where ventilation comes in. Absent proper roof ventilation that allows controlled airflow through the inner roof or attic area, a home may suffer from condensation, humidity and even mold. With proper ventilation, air flows into one side of the inner roof or attic and out the other. A roof that is more complex can have more than one point where air flows in and out.

Homes in Georgia are required to have adequate roof ventilation under the code provisions of the IRC. This includes houses that have attics as well as those with ceilings that attach directly to the roof rafters.

Roofs must be vented, with openings between 1/16 inch and 1/4 inch. The roofers must install protection over the vent openings to prevent rain and snow from entering. For any vent openings that are 1/4 inch or more, roofers must install a corrosion-resistance wire cloth screen that meets the 1/16-inch and ¼-inch dimensions.

Residential roof requirements in Georgia require the installation of sheet metal flashing and counterflashing. Flashing is material used to prevent water leakage around chimneys and areas of the roof where it intersects with a wall. The system usually consists of both metal base flashing and counterflashing in vulnerable areas such as around a chimney.

The base flashing is installed at the bottom of the chimney while counterflashing is installed on top of the flashing into the brickwork of the chimney. The counterflashing assures that water does not go past the base flashing and instead flows down the roof or through the gutter.

Re-roofing is a term of art and does not simply refer to stripping off an old asphalt shingle roof and installing a new one. Rather, as used in the Georgia codes, re-roofing is a specific procedure that can repair minor roof problems at a lower cost than replacing the roof. The re-roofing procedure involves laying new shingles on top of the existing shingles.

Generally, the existing shingles are damaged, which is the reason the homeowner might consider re-roofing. Since the roofers are not required to tear off and replace the existing roof, re-roofing takes less time and costs a lot less. While generally re-roofing is permitted in Georgia, it is forbidden in certain situations. Homeowners cannot re-roof a house if the old roof is dilapidated or waterlogged or has more than one layer of roofing material already in place.