|
Built-Up
Roofing
Specifications |
6.15.14 Installing Ballasted, Unadhered PRMA Roof
Insulation
Over Built-Up Roof Membranes
The following are general recommendations for installing
ballasted PRMA roof insulation over built-up roof membranes.
6.15.15 Separator Sheet: (If required) Over Type I or Type II
asphalt, use a 4 mil (0.1 mm) thick (minimum) polyethylene
separator sheet installed directly over the asphalt with 2" (51
mm) minimum laps at all seams.
6.15.16 Insulation: Place extruded polystyrene insulation
directly on the membrane (or separator sheet if used) with
channel side down. The insulation boards should be tightly
butted together. The maximum allowable gap between boards
is 3/8 " (9.5 mm). The boards shall be installed to within and no
closer than ¾" (19 mm) of all projections and cant strips.
6.15.17 For multilayer installations, install subsequent layers of
insulation, unattached over the first layer. Stagger all joints in
relation to the underlying layer. The bottom layer in multilayer
applications must be at least 2" (51 mm) thick and as thick or
thicker than the top layer.
6.15.18 Warning: Extruded polystyrene insulation is
combustible and may constitute a fire hazard if improperly used
or installed. It should be adequately protected. Use only as
directed by the specific instructions for this product. This
material should NEVER be exposed to an open flame or other
source of ignition.
All roof deck systems over which the PRMA system is installed
should provide an adequate fire barrier for the extruded
polystyrene insulation.
For proper protection of plastic foam in storage, consult the
National Fire Protection Association (NFPA) standards or the
authority having jurisdiction.
6.15.19 Fabric: Loose lay an approved fabric over the
extruded polystyrene roof insulation, with all joints lapped a
minimum of 12" (305 mm). There should not be any end laps
within 6' (1.83 m) of the perimeter. The fabric should extend 2" -
3" (51 - 76 mm) above the stone at the perimeter and at all
penetrations.
Wetting the fabric is helpful in holding it in place on the
insulation until the ballast is installed.
6.15.20 Ballast: Apply the correct size ballast at the rate of
1000 -1200 lbs. per square (10 - 12 lbs. per sq. ft. [48.8 - 58.6
kg/m2]), over the fabric, as the fabric is being laid out in the
field of the roof. For a width of 4' (1.22 m) at the roof perimeter
or penetrations, install ballast at the rate of 20 lbs. per sq. ft.
(97.6 kg/m2) or pavers at the rate of 22 lbs. per linear foot (32.7
kg/lin. m). If pavers are used, the fabric is not required. Pavers
must be placed on pedestals. Pedestals can be either
commercially available products or 6" (152 mm) squares of
DynaTred Plus.
Ballast should be washed ¾" (19 mm) gravel or crushed stone
¾ " (19 mm), with fines (smaller than ½ " [13 mm]) accounting for not
less than 10% or more than 60%. This gradation is similar to
ASTM D 448, gradation #57.
6.16 Coal Tar General Information
6.16.1 JM acknowledges that ASTM D 450, Type I Coal
Tar Pitch is used in certain gravel surfaced built-up
roofing system specifications. However, coal tar pitch is
not to be used within JM Roofing Systems.
Danger: Coal Tar is considered a hazard by inhalation,
ingestion and skin contact. The International Agency for
Research on Cancer (IARC) has classified coal tar as an
agent which is carcinogenic to humans (Group 1). JM
does not make or sell a coal tar pitch waterprooflng
agent, and does not recommend its use. Alternative
materials, such as asphalt should be utilized.
