Code of Massachusetts Regulations › 780 CMR - STATE BOARD OF BUILDING REGULATIONS AND STANDARDS › Chapter 16 - Structural Design › Section 1609 - WIND LOADS › Subsection 1609.5 - Roof systems

Current through Register 1525, July 5, 2024
1609.5.1
Roof deck.
The roof deck shall be designed to withstand the wind
				pressures determined in accordance with ASCE 7.
1609.5.2
Roof coverings.
Roof
				coverings shall comply with Section 1609.5.1.
Exception:
Rigid tile roof coverings that are
				  air permeable and installed over a roof deck complying with Section 1609.5.1
				  are permitted to be designed in accordance with Section 1609.5.3.
Asphalt shingles installed over a roof deck complying with
				  Section 1609.5.1 shall comply with the wind-resistance requirements of Section
				  1507.2.7.1.
1609.5.3
Rigid tile.
Wind loads on rigid tile roof coverings shall be determined
				in accordance with the following equation:
M
a =
q
h
C
L
bLL
a[1.0
							 -
GC
p]
(Equation
							 16-33)
For SI:
M
a =
Click to view
							 image
where:
b
=
Exposed width, feet (mm) of the roof tile.
C
L
=
Lift coefficient. The lift coefficient for concrete and
							 clay tile shall be 0.2 or shall be determined by test in accordance with
							 Section 1716.2.
GC
p
=
Roof pressure coefficient for each applicable roof
							 zone determined from Chapter 6 of ASCE 7. Roof coefficients shall not be
							 adjusted for internal pressure.
L
=
Length, feet (mm) of the roof tile.
L
a
=
Moment arm, feet (mm) from the axis of rotation to the
							 point of uplift on the roof tile. The point of uplift shall be taken at
							 0.76
L
from the head of the tile and the middle of the exposed
							 width. For roof tiles with nails or screws (with or without a tail clip), the
							 axis of rotation shall be taken as the head of the tile for direct deck
							 application or as the top edge of the batten for battened applications. For
							 roof tiles fastened only by a nail or screw along the side of the tile, the
							 axis of rotation shall be determined by testing. For roof tiles installed with
							 battens and fastened only by a clip near the tail of the tile, the moment arm
							 shall be determined about the top edge of the batten with consideration given
							 for the point of rotation of the tiles based on straight bond or broken bond
							 and the tile profile.
M
a
=
Aerodynamic uplift moment, feet-pounds (N-mm) acting
							 to raise the tail of the tile.
q
h
=
Wind velocity pressure, psf
							 (kN/m2) determined from Section 6.5.10 of ASCE
							 7.
Concrete and clay roof tiles complying with the following
				  limitations shall be designed to withstand the aerodynamic uplift moment as
				  determined by this section.
1. The
				roof tiles shall be either loose laid on battens, mechanically fastened, mortar
				set or adhesive set.
2. The roof
				tiles shall be installed on solid sheathing which has been designed as
				components and cladding.
3. An
				underlayment shall be installed in accordance with Chapter 15.
4. The tile shall be single lapped
				interlocking with a minimum head lap of not less than 2 inches (51
				mm).
5. The length of the tile
				shall be between 1.0 and 1.75 feet (305 mm and 533 mm).
6. The exposed width of the tile shall be
				between 0.67 and 1.25 feet (204 mm and 381 mm).
7. The maximum thickness of the tail of the
				tile shall not exceed 1.3 inches (33 mm).
8. Roof tiles using mortar set or adhesive
				set systems shall have at least two-thirds of the tile's area free of mortar or
				adhesive contact.