ROOFING REQUIREMENTS
BUILDING INSPECTIONS DIVISION: 217/424-2787
V. International Code Highlights (2015 IRC Chap. 9 / 2015 IBC Chap. 15)
A. Roof assemblies shall be designed and installed in accordance with the referenced codes and the
approved manufacturer’s instructions.
B. Flashings shall be installed in a manner that prevents moisture from entering the structure at wall
and roof intersections, at changes in roof slope or direction, and around roof openings. Metal
flashing shall be corrosion resistant and a minimum of .019” thick (No. 26 galvanized).
C. A cricket or saddle shall be installed on the ridge side of any chimney or penetration more than
30” wide as measured perpendicular to the slope. Cricket or saddle coverings shall be sheet metal
or of the same material as the roof covering.
D. Underlayment materials must be labeled ASTM D 226, D 1970, D 4869, or D6757. Underlayment
for asphalt shingles on roof slopes 2:12 to 4:12 shall be (2) layers applied in the following manner:
apply a 19” strip starting at the eave, then apply 36” wide sheets starting at the eave overlapping
successive sheets 19”. For roof slopes 4:12 or greater, underlayment shall be (1) layer applied in
shingle fashion starting at the eave and lapped 2”. End laps shall be minimum 4” and offset by 6’.
E. An ice barrier consisting of (2) layers of underlayment cemented together, or a self-adhering
polymer-modified bitumen sheet, shall be installed under the drip edge and extend from the
lowest edges of all roof surfaces to a point not less than 24” inside the exterior wall line. On roof
slopes 8:12 or greater, the ice barrier shall be applied not less than 36” measured along the roof
slope from the eave. It is recommended to apply felt over the ice barrier. An ice barrier is not
required on roofs of detached accessory structures not containing conditioned floor area.
F. Asphalt shingles shall have the minimum # of fasteners required by the manufacturer, but not less
than (4) fasteners per strip shingle or (2) fasteners per individual shingle.
G. Valley linings shall be installed in accordance with the manufacturer’s instructions before applying
shingles.
H. 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.
I. Roof replacement shall include the removal of existing layers of roof coverings down to the roof
deck. Where the existing roof assembly includes an ice barrier membrane that is adhered to the
roof deck, the existing ice barrier membrane can remain in place and be covered with an
additional layer of ice barrier membrane installed per code.
J. A roof re-cover (installation of a new roof covering over an existing roof covering) shall not be
permitted 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 covering is not adequate as a base for additional roofing.
2. Where the existing roof covering is slate, clay, cement or asbestos-cement tile.
3. Where the existing roof has two or more applications of any type of roof covering.
K. These code highlights taken from the International codes are not all-inclusive. Consult the
referenced codes for any items not specifically addressed.