Issue: DCA10-DEC-079 by Richard Mihalich, Chief Building Official of City of South Daytona. The Petitioner seeks a declaratory statement requesting clarification of whether new roof coverings can be installed over the existing coverings of a town-home built in 1984. The Petitioner states the town home in question is rectangular and has a flat roof system surrounded on all four sides by a parapet. Each of the parapets has openings with gutters to facilitate drainage of the roof.

Additionally, the Petitioner states that the condition of the existing covering is such that it complies with the conditions stated in section 1510.3 of the Florida Building Code (FBC), Building, and section 611.3 of the FBC, Existing Building, to allow the new covering to be placed over the existing roof system. The Petitioner further states that puddles exist on the roof after precipitation has ceased, and if not evaporation, they would remain indefinitely.

The Petitioner request that the Commission issue a Declaratory Statement to answer the following questions:

Question #.1. Under the stated existing conditions of the roofing systems in the town-home complex, can a new modified bitumen roofing system, as defined in Section 1507.11 of the FBC be installed over the existing roof coverings without the addition of the required minimum slope of ¼” in 12” for roofing covering systems requiring that minimum slope?

Question #.2. Under the stated conditions of the roofing systems in the town-home complex, if the standing water evaporates within 48 hours, does this meet the definition of Positive Roof Drainage?

Question #. 3. Do the conditions of the townhome, as stated above, constitute Positive Roof Drainage as defined in Section 1502, Definition, FBC, thereby allowing the roof to be recovered as opposed to being replaced and the required minimum one-fourth unit in twelve slope installed?

Background:

2007 Florida Building Code, Building:

Section 1502 Definitions:

POSITIVE ROOF DRAINAGE. The drainage condition in which consideration has been made for all loading deflections of the roof deck, and additional slope has been provided to ensure drainage of the roof within 48 hours of precipitation.

REROOFING. The process of recovering or replacing an existing roof covering. See "Roof recover" and "Roof replacement."

ROOF RECOVER. The process of installing an additional roof covering over a prepared existing roof covering without removing the existing roof covering.

ROOF REPLACEMENT. The process of removing the existing roof covering, repairing any damaged substrate and installing a new roof covering.

Section 1507.11 Modified bitumen roofing. The installation of modified bitumen roofing shall comply with the provisions of this section.

1507.11.1 Slope. Modified bitumen membrane roofs shall have a design slope of a minimum of one-fourth unit vertical in 12 units horizontal (2-percent slope) for drainage.

1507.11.2 Material standards. Modified bitumen roof coverings shall comply with CGSB 37-GP-56M, ASTM D 6162, ASTM D 6163, ASTM D 6164, ASTM D 6222, ASTM D 6223, ASTM D 6298 or ASTM D 6509.

Section 1510, Reroofing:

1510.1 General. Materials and methods of application used for recovering or replacing an existing roof covering shall comply with the requirements of Chapter 15.

Exception: Reroofing shall not be required to meet the minimum design slope requirement of one-quarter unit vertical in 12 units horizontal (2-percent slope) in Section 1507 for roofs that provide positive roof drainage.

1510.2 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.

1510.3 Recovering versus replacement. New roof coverings shall not be installed without first removing all existing layers of roof coverings where any of the following conditions occur:

1. Where the existing roof or roof covering is water soaked or has deteriorated to the point that the existing roof or roof covering is not adequate as a base for additional roofing.

2. Where the existing roof covering is wood shake, slate, clay, cement or asbestos-cement tile.

3. Where the existing roof has two or more applications of any type of roof covering.

4. When blisters exist in any roofing, unless blisters are cut or scraped open and remaining materials secured down before applying additional roofing.

5. Where the existing roof is to be used for attachment for a new roof system and compliance with the securement provisions of 1504.1 cannot be met.

Exceptions:

1. Complete and separate roofing systems, such as standing-seam metal roof systems, that are designed to transmit the roof loads directly to the building's structural system and that do not rely on existing roofs and roof coverings for support, shall not require the removal of existing roof coverings.

2. Reserved.

3. The application of a new protective coating over an existing spray polyurethane foam roofing system shall be permitted without tear-off of existing roof coverings.

2007 Florida Building Code, Existing Building:

SECTION 611 REROOFING

611.1 General. Materials and methods of application used for recovering or replacing an existing roof covering shall comply with the requirements of Chapter 15 of the Florida Building Code, Building or Chapter 9 of the Florida Building Code, Residential, as applicable. Roof repairs to existing roofs and roof coverings shall comply with the provisions of this code.

Exception: Reroofing shall not be required to meet the minimum design slope requirement of ¼:12 in Section 1507 of the Florida Building Code, Building for roofs that provide positive roof drainage (high-velocity hurricane zones shall comply with Sections 1515.2.2.1 and 1515.2.2.2 of the Florida Building Code, Building).

611.1.1 Not more than 25 percent 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.

611.2 Structural and construction loads. The 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 roof covering system.

611.3 Recovering versus replacement. New roof coverings shall not be installed without first removing existing roof coverings where any of the following conditions occur:

1. When the old roofing is water-soaked or deteriorated to the point that it is not suitable as a base for additional roofing.

2. When blisters exist in any roofing, unless blisters are cut or scraped open and nailed down before applying additional roofing.

3. When the existing roof surface is gravel or the like, the gravel shall be thoroughly removed or all loose gravel removed and approved base material installed before applying additional roofing.

4. When existing roof is slate or the like.

5. When sheathing or supports are deteriorated to the point that the roof structural system is not substantial enough to support recovering.

6. When the existing roof has two or more applications of any type roofing material. Conformance with this item shall make replacement mandatory.

Exceptions:

1. Building and structures located within the High-Velocity Hurricane Zone shall comply with the provisions of Sections 1512 through 1525 of the Florida Building Code, Building.

2. When the structural deck is concrete and the existing roof is firmly attached to the deck, the roof shall be removed down to a minimum of three plies of moisture-free felts.

3. When otherwise approved by the building official.

4. Wood shingles or shakes shall not be placed over more than one application of wood or asphalt shingles. Wood shingles or shakes may be placed over existing shakes when installed in accordance with Cedar Shake and Shingle Bureau recommendations.

Staff Recommendations:

Answer: Yes. According to Section 1510.1, Exception, of the FBC, Building, and Section 611.1, Exception, of the FBC, Existing Building, the minimum slope of ¼” in 12” is not required for the reroofing project in question as long as the roof will provide positive roof drainage as defined in Section 1502 of the FBC, Building.

Question #.2. Under the stated conditions of the roofing systems in the town-home complex, if the standing water evaporates within 48 hours, does this meet the definition of Positive Roof Drainage?

Answer: No. According to the definition of the term “Positive Roof Drainage”, additional slope must be provided to ensure drainage of the roof within 48 hours of precipitation.

Answer: see answers to Question #1 and #2 above.