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Last Revision
February 27, 2017
Building Code Conflicts
Below are some examples of conflicts, pertaining to
roofing, between the International Building
Code (IBC), the International Residential Code (IRC), the International Code
Council (ICC) Evaluation Services Current and Legacy ICC-ES Reports,
and Manufacturer's Specifications, or Manufacturer Association Manuals.
Whichever is more restrictive is used in our
roofkey Roofing Guidelines
and Roof Inspection Service because
weather conditions cannot tell the difference between a roof on a residential
building or on a commercial building. And there are weather conditions that do
occur here in Colorado that affect the performance of roofing materials and
accessories and
their installation.
Examples of Building Code Conflicts
- Eave and Rake Metal Drip Edge:
The IBC requires a metal drip edge at both the eaves and the
rakes of an Asphalt Shingle roof. The IRC does not.
We will be using the IBC
requirements for both residential and commercial buildings and
will write a correction notice for missing rake metal drip edge on Asphalt
Shingle roofs.
- Hail Damage Prone Areas: The
IRC recognizes that most of the Front Range and the Eastern
Plains of Colorado including the Metro Denver area is located in
a Moderate Hail Exposure Area, which requires the removal of all roof coverings
to the deck when installing Asphalt Shingles. Only one layer of Asphalt
Shingles is permitted because a single layer is more resistant to damage from
hail. The IBC does not recognize hail damage prone areas. Roof damage from
hail is the same whether the roof is on a commercial building or residential
building. So we will be using the IRC criteria and write a
correction notice for more than one layer of Asphalt Shingles.
- Wind Driven Snow Areas: The
ICC Evaluation Service's legacy reports for decades
recognized areas with wind driven snow which require both vertical battens to be
installed under all horizontal battens with all Tile roofs. Low sloped roofs
require 2 plies of base felts applied in shingle fashion since water easily penetrates through the tile and
soaks the underlayment. Since wind driven snow frequently blows up under the
tiles and also soaks the underlayment, the underlayment should be treated the
same on all slopes. Tile roofs require both vertical and horizontal battens and
Code approved ASTM numbered underlayments of either 2 plies of Type II
underlayment
(30 pound base felt) or a single ply of an approved ASTM numbered 90 lbs. rolled roofing
or Ice and Water Membrane.
- This same requirement
is stated again in the Concrete and Clay Tile Roof Design Criteria Manual for Cold and
Snow Regions: "Felt underlayments are intended to protect the building
from wind driven snow or rain. They are required by code.
Even a good tile may allow a dry light snow to blow in under it and onto
the felt where melting will eventually occur. On a well designed
tile roof, the underlayment generally wears out before the tile.
Two layers of ASTM D226, Type II, No. 30 asphaltic felt overlaid in
shingle fashion is the recommended minimum."
- So we, like a few other City/County Building Departments,
also
recognize that this is a Wind Driven Snow Area and will write a
correction notice for missing vertical battens or risers and/or the approved
above listed underlayments and listed in our
roofkey
Roofing Guidelines web page. Any approved alternate underlayment equal to ASTM
D226 Type II underlayment (30 pound base felt) must also be applied in the same
shingle fashion with
2-ply coverage.
- Eave Ice and Water Membrane: The 2006
IBC and IRC was changed to better define when the
use of an ice and water membrane is required. The current definition all
through Chapter 15 of the IBC and Chapter 9 of the IRC is:
"In areas where
there has been a history of ice forming along the eaves causing a backup of
water a membrane that consists of at least two layers of underlayment cemented
together or of a self-adhering polymer modified bitumen sheet shall be used in
lieu of normal underlayment" In other words, if your area has ice
forming along the eaves which by the very nature of ice damming backs up
water, you must use an ice and water membrane. The entire Colorado Front
Range as well as most of the rest of Colorado has ice forming at the eaves
to various degrees every year from 2" to as much as 18" as in
January - February of 2007. Some Building Departments are unaware of the damage
ice damming has caused their citizens because Building Permits are generally not
obtained to make the necessary repairs. So, like some Cities and Counties, we
recognize there is ice forming along the eaves and will write a
correction notice for missing ice and water membranes at the eaves.
- Weather Blocking Material (approved flashing): The
ICC Evaluation Legacy Reports and the Tile Manufacturer's
Installation Manuals require weather-blocking material (approved flashing) to be
installed. From the 2010 Tile Manufacturer's Manual
"Openings at the hips,
ridges, and headwalls including chimneys, skylights, solar panels, and down
slope horizontal abutments shall be fitted with weather blocking material
to
keep water on the surface of the field tile". It is also required for flashing
at jacks and vents. Flashing on the surface of a tile roof is needed in areas
where debris can accumulate as also stated in the manufacturer's manual and is
common sense. Debris will accumulate just from trees in all areas. All other
types of roofing material have always required flashing to be placed so that the
water is kept on the surface of the field roofing material for obvious reasons.
Therefore we will write a correction notice for missing primary flashing
(flashing on surface of tiles) as well as secondary flashing (flashing over the
underlayment but under the tile) at all Jacks, Vents, Head Walls, Rake Walls,
Chimneys, Skylights, Curbs, Swamp Cooler Ducts, Hips, Ridges and any Other
Protrusions through the tile roof to help keep as much water as possible on the
surface of the tile and limit the access for debris and critters to get in under
the tile. (See our
roofkey
Roofing Guidelines web page for Clay and Concrete Tile under Primary
Flashing and/or Weather Blocking Material for more information.