Dow Protected Membrane Roof EN - Manual (Page 13)

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Components
P A V E R S
Description
Concrete slab pavers or inter-
locking pavers can be used to
supplement or replace conven-
tional stone ballast requirements
and create a surface for rooftop
decks, walkways, terraces, gardens
and similar applications.
Note: For structural plaza deck
design, such as for parking decks
and other high-traffic areas, the
design is the responsibility of an
architect and/or structural engineer.
Function
Note: For additional information,
see “Ballast” on page 10.
Narrow roof walkways for
access: Pavers can be placed to
facilitate access to rooftop
equipment.
Prevent wind scouring: In
exposed areas or areas of high
winds, pavers may be required.
In certain conditions, the pavers
should be strapped together
using galvanized or stainless
steel straps, mechanically fas-
tened to each paver.
Perimeter ballast: Additional
ballast is required around the
building perimeter in a PMR
design. Depending on the
design, pavers can be installed
instead of conventional stone
ballast.
Plaza-deck design: For light
traffic requirements, the stone
ballast can be replaced with
concrete pavers completely. In
many cases, the pavers must be
raised from the surface of the
fabric and insulation. See
“Installation Notes” for details.
Specification
PAVERS
Concrete pavers shall be man-
ufactured from minimum 3,000
lb/in
2 concrete with a minimum
weight of 18 lb/ft 2 .
When ribbed insulation is not
used and the total area to be
covered by pavers is more than
10 percent and the location has
more than 3,000 heating degree-
days, pavers should be raised
from the surface of the fabric
and insulation using spacers
to maintain at least a 3/16"
ventilating air space (“diffusion
open” design). The spacer can be:
• 1" thick insulation cut into
6" square blocks and placed
under the four corners of the
paver (limited to 108 lb/in
2
live loading)
• Preformed pavers with at least
a 3/16" foot in each corner or
ribbed undersurface
• Paver pedestal of injection
molded, weathering-grade plastic,
installed under each corner
(e.g., PAVE-EL by Envirospec Inc.,
Terra-Tabs by Wausau Tile, etc.)
• Layer of pea gravel 1" (min.)
free of fines
Note: This air space is not required
if the pavers are covering only a
limited area (less than 10 percent
of roof area), such as corners or
narrow roof walkways.
PAVER STRAPPING AND
FASTENERS (IF REQUIRED):
Straps shall be of 22 gauge
galvanized or stainless steel,
3" wide and 12' long.
Fasteners shall be 1/4" x 1-1/4"
corrosion-resistant metal
anchors, expanded in pre-drilled
holes (e.g., Zamac Nailin #2814
by Powers Fasteners, Inc).
Installation Notes
When pavers cover more than
10 percent of the insulation sur-
face and are located in climates
with more than 3,000 heating
degree-days, create a 3/16" space
between the insulation and
the underside of the pavers.
In colder climates, the air space
will minimize any freeze-thaw
spalling on the concrete and
moisture build-up in the insula-
tion due to vapor drive from the
inside.