Dow Protected Membrane Roof User Manual

I N S T A L L A T I O N I N F O R M A T I O N

United States

C O M M E R C I A L

Protected Membrane Roof
Installation Guidelines

P M R F I R S T . . . T O L A S T .

Table of Contents

O V E R V I E W . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

G L O S S A R Y . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

C O M P O N E N T S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

STYROFOAM™Extruded Polystyrene Insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Fabric . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Ballast . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Pavers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

All Other Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

C O N D I T I O N S , I S S U E S A N D R A T I N G S . . . . . . . . . . . . . . . . . . . . . . . . 15

Special Conditions and Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Cold Rain Phenomenon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Moisture Absorption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Dimensional Stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Green Roof Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Finding Leaks in a PMR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Low Temperature Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

High Temperature Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Membrane Seam Failure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Plant Growth on PMR Assemblies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

T A B L E O F C O N T E N T S

Fire and Wind Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Test Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

ULI Hourly Fire Resistance Ratings for PMR – Steel Deck . . . . . . . . . . . . . . . . . . . . . . . 21

ULI Hourly Fire Resistance Ratings for PMR – Concrete Deck . . . . . . . . . . . . . . . . . . . . 22

ULI Hourly Fire Resistance Ratings for PMR – Other . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

ULC Hourly Fire Resistance Ratings for PMR – Metal Deck . . . . . . . . . . . . . . . . . . . . . . 23

ULC Hourly Fire Resistance Ratings for PMR – Concrete Deck . . . . . . . . . . . . . . . . . . 24

FM Hourly Fire Resistance Ratings for PMR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

FM Class 1 Fire and Wind Uplift . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

®™Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow

1

Overview

C H A N G I N G T H E S E Q U E N C E

Protected membrane roofing’s

breakthrough contribution to

O V E R V I E W

flat roof technology was the
incorporation of an “upside­down” approach to insulating
the roof: placing the insulation
on top of the waterproof mem­brane to improve the membrane’s
effectiveness and the insulation’s
efficiency.

This advancement was made
possible in large part by the use
of STYROFOAM™extruded poly­styrene insulation, whose
closed-cell, water-resistant quali­ties have proven to be a key
component in protected mem­brane roof (PMR) systems.

A conventional roof places
the membrane on top of the
insulation, leaving the mem­brane vulnerable to extreme
temperature changes, freeze­thaw conditions and physical
abuse from heavy foot traffic
(Figure 1).

The PMR system places the
insulation on top of the mem­brane, protecting the roofing
membrane from extreme tem­perature changes and physical
abuse (Figure 2).

The main difference between
PMR and conventional roofing
is the sequence in which the
materials are applied. The key
to the PMR system is that the
insulation is placed on top of
the waterproofing membrane.
This configuration protects the
membrane, resulting in superior
long-term performance and
durability.

Membrane

STYROFOAM™
Extruded
Polystyrene
Insulation

Deck

Figure 1: Conventional Roof With Membrane Above
the Insulation (depending upon building and climate
conditions, a vapor barrier may also be used)

Ballast

Filter
Fabric

STYROFOAM™
Extruded
Polystyrene
Insulation

Membrane

Deck

Figure 2: PMR With Membrane Below the Insulation

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®™Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow

Overview

C H A N G I N G T H E S E Q U E N C E

Advantages of PMR

All flat roof assemblies consist
of the same basic elements
assembled in a seemingly logical
order: a deck (composed of wood,
metal or concrete), covered with
insulation and topped with a
waterproofing membrane. A
protected membrane roof can
employ the same elements, but
the membrane is positioned
under the insulation, offering
superior long-term performance
and durability.

PMR assemblies:

• Maintain the membrane at a

nearly constant temperature,

close to the temperature of

the building’s interior; this

minimizes the stresses on the

membrane by reducing the

harmful effects of freeze-thaw

cycling, thermal cycling and

excessive heat

• Protect the membrane from

weathering, foot traffic and other

types of physical abuse – both

during and after construction

• Allow year-round construction

since the roof is waterproofed

first, then insulated

• Permit easy removal and re-

installation of the ballast and

insulation for making repairs

or for constructing additional

stories. In addition, a protected

membrane roof provides an

environmentally preferred

option to reuse the insulation

• Allow for a range of ballast

options – stone, precast paving

slabs, green roof, interlocking

stone or concrete – depending

on use and aesthetic

considerations

• Are compatible with a range

of membrane types

• Eliminate the need for a sepa-

rate vapor retarder

PROVIDE DURABILITY
AND PROTECTION

With the membrane positioned
under the insulation, the choice
of insulation becomes an impor­tant consideration. The insulation
must be able to withstand wet
environments (without sacrificing
insulation performance) and
foot traffic during and after
construction, while continuing
to perform over time.

Because of its durability and
outstanding moisture-resistant
qualities, STYROFOAM™extruded
polystyrene insulation delivers
exceptional performance in
roofing and plaza applications.

• Provides excellent moisture

resistance and long-term

R-value*

• Offers exceptional durability

to extend the life of the plaza

or roof

• Protects the membrane against

weathering, physical abuse

and damage

• Maintains the membrane at a

relatively constant temperature

• Controls dew point location

O V E R V I E W

®™Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow
*R means resistance to heat flow. The higher the R-value, the greater the insulating power.

3

Glossary

Absorption: the ability of a

material to absorb quantities of

G L O S S A R Y

gases or liquids, such as moisture.

Accelerated Weathering: an

experimental test where a material
is exposed in a controlled
environment to various elements
(heat, water, condensation or
light) to magnify the effects
of weathering. The material’s
physical properties are measured
before and after the process to
identify any detrimental effects
of weathering.

Aggregate: rock, stone, crushed

stone, crushed slag or water­worn gravel used for ballasting
a roof system.

Aging: the effect on materials

exposed to an environment for
a defined time.

Alligatoring: the cracking of the

exposed bitumen on a built-up
roof, producing a pattern of cracks
similar to an alligator’s hide.

Asphalt: a dark brown or black

substance left as a residue when
processing crude oil or petroleum.
Asphalt may be further refined
to conform to various roofing
grade specifications.

Asphalt Emulsion: a mixture of

asphalt particles and an emulsi­fying agent, such as bentonite
clay and water.

Ballast: an anchoring material,

such as stone or precast
concrete pavers, used to hold
insulation and/or roof mem­branes in place.

Base Ply: the bottom ply of

roofing in a roof membrane or
roof system.

Base Sheet: an impregnated,

saturated or coated felt placed as
the first ply in some multi-ply
built-up and modified bitumen
roof membranes.

Blocking: sections of wood built

into a roof assembly, usually
attached above the deck and
below the membrane or flashing,
used to stiffen the deck around
an opening, act as a stop for
insulation, support a curb or to
serve as a nailer for attachment
of the membrane and/or flashing.

Built-up Roof (BUR) Membrane:

a continuous, semi-flexible multi­ply roof membrane, made up of
plies or layers of saturated felts,
fabrics or mats with bitumen in
between.

Cant Strip: a beveled or triangular-

shaped strip of wood or other
suitable material used to transi­tion from the horizontal surface
of a roof deck or rigid insulation
to a vertical surface.

Caulking: sealing and making

weather-tight the joints, seams
or voids between adjacent units
using a sealant.

Compatible Materials: two

or more substances that can
be mixed, blended or attached
without separating, reacting or
affecting the materials adversely.

Condensation: the conversion

of water vapor or other gas to
liquid state as the temperature
drops or atmospheric pressure
rises. (Also see Dew Point.)

Counterflashing: formed metal

sheeting secured on or into
another surface used to protect
the upper edge of the membrane
or underlying metal flashing
and associated fasteners from
exposure to the weather.

Dead Load: permanent non-

moving load that results from the
weight of a building’s structural
and architectural components,
mechanical and electrical
equipment, and the roof
assembly itself.

Deck: a structural component of

the roof of a building designed
to safely support the design dead
and live loads, including the
weight of the roof systems, and
the additional live loads required
by the governing building codes.
Decks are either non-combustible
(e.g., corrugated metal, concrete
or gypsum) or combustible (e.g.,
wood plank or plywood) and are
the substrate used to apply the
roofing or waterproofing system.

Design Load: load specified

in building codes or standards
published by federal, state,
county or city agencies, or in
owners’ specifications to be
used in the design of a building.

Dew Point: the temperature

where water vapor condenses
in cooling air at the existing
atmospheric pressure and
vapor content. Cooling at or
below the dew point will cause
condensation.

Dynamic Load: any load that is

non-static, such as a wind load
or a moving live load.

Curb: a raised roof location

relatively low in height.

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®™Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow

Glossary

Fabric: a woven cloth or material

of organic or inorganic filaments,
threads or yarns. Can be used
as a reinforcement in certain
membranes and flashings or
used in a protected membrane
roof application to reduce the
ballast requirements.

Flashing: materials used to

weatherproof or seal the roof
system edges at perimeters,
penetrations, walls, expansion
joints, valleys, drains and other
places where the roof covering
is interrupted or terminated.

Gravel Stop: a low profile,

upward-projecting metal edge
flashing with a flange along the
roof side, usually formed from
sheet or extruded metal. Installed
along the perimeter of a roof to
provide a continuous finished
edge for roofing material.

Humidity: the amount of

moisture contained in the
atmosphere. Generally expressed
as percent relative humidity
(% RH). It is the ratio of the
amount of water vapor actually
present in the air, compared to
the maximum amount that the
air could contain at the same
temperature.

Inverted Roof Membrane
Assembly (IRMA): same as

protected membrane roof (PMR)
assembly, where a closed-cell
insulation (e.g., STYROFOAM
insulation) and ballast are placed
over the roof membrane.

™

Live Load: temporary load

that the roof structure must be
designed to support, as required
by governing building codes.
Can include people, installation
equipment, vehicles, wind,
snow, ice or rain, etc.

Loose-laid Membrane: mem-

brane that is not attached to the
substrate except at the perimeter
of the roof and at penetrations.
Typically, a loose-laid membrane
is held in place with ballast.

Mechanically Fastened
Membrane: membrane that is

attached at defined intervals to
the substrate, using various fas­teners and/or other mechanical
devices.

Membrane: a flexible or

semi-flexible material that water­proofs (excludes water) a roof.

Parapet Wall: that part of a

perimeter wall immediately
adjacent to the roof, which
extends above the roof.

PMR: protected membrane roof.

Positive Drainage: the drainage

profile of a deck, considering
the roof slope and loading
deflections to ensure the roof
deck drains within 48 hours of
rainfall during ambient drying
conditions.

Ridge: highest point on the roof

where two roof areas intersect.

Roof Assembly: an assembly

of interacting roof components
(includes the roof deck, vapor
retarder [if present], insulation
and roof covering).

Roof Slope: the angle a roof

surface makes with the horizon­tal. Typically expressed as a ratio
of rise to run, such as 4:12, or as
a percent.

Square: 100 square feet of roof

area.

Substrate: the surface on which

the roofing or waterproofing
membrane is applied (e.g., the
structural deck or insulation).

Vapor Retarder: a material that

restricts the movement of water
vapor.

Wind Uplift: the force caused by

the deflection of wind at roof
edges, roof peaks or obstructions,
causing a drop in air pressure
immediately above the roof
surface (e.g., suction). Uplift may
also occur from air movement
from underneath the roof deck,
causing the membrane to balloon
and pull away from the deck.

G L O S S A R Y

®™Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow

5

Components

S T Y R O F O A M

™

E X T R U D E D P O L Y S T Y R E N E I N S U L A T I O N

Description

STYROFOAM™extruded
polystyrene insulation is a rigid,
closed-cell insulation, ideally
suited and designed for PMR
installations. Because of the
properties imparted during the
extrusion process combined
with the hydrophobic nature
of polystyrene, STYROFOAM
insulation has a high resistance
to both water and water vapor,
providing demonstrated long­term mechanical and thermal
performance.

The boards are available in a
range of thicknesses, densities,
and edge and surface treatments.

STYROFOAM

™

ROOFMATE

An extruded polystyrene foam insulation
providing excellent moisture resistance,
durability and long-term R-value. Ideal
for installation above waterproofing or
roofing membranes in PMR applications.

™

STYROFOAM™Ribbed ROOFMATE

An extruded polystyrene foam insulation
board with 1/4" x 1/2" drainage channels
on the bottom long edge of each board.
The top surface of the board has ribs that
form corrugations in the long dimension
of the board.

Designed for installation above water­proofing or roofing membranes in PMR
applications that use pavers as ballast.
Pavers can be installed directly over the
ribbed foam surface without needing
pedestals.

™

STYROFOAM™PLAZAMATE

A high-density extruded polystyrene foam

C O M P O N E N T S – S T Y R O F O A M E x t r u d e d P o l y s t y r e n e I n s u l a t i o n

insulation board designed to be installed
above waterproofing or roofing membranes
in most plaza deck applications.

™

STYROFOAM™Highload 40, 60 and 100

An extruded polystyrene foam insulation
board with high compressive strength
developed specifically for in-ground
application and freezer floors. The prod­ucts are also well-suited for plaza decks
and protected membrane roofs that must
withstand heavy traffic.

6

®™Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow

Components

S T Y R O F O A M

™

E X T R U D E D P O L Y S T Y R E N E I N S U L A T I O N

Function

Provide thermal properties:

STYROFOAM™extruded poly­styrene insulation has a high
aged thermal resistance (R-value)
when compared with competi­tive roof insulations.

Provide membrane protection:

By installing the insulation over
the membrane, the membrane
is kept at a relatively constant
temperature year-round and
protected from weathering,
mechanical damage and abuse.

Specification

The insulation shall meet
ASTM C578-05 (Type V, VI or
VII depending on the required
properties) or CAN/ULC S701
Type 4.

Install required thickness of
STYROFOAM™extruded poly­styrene insulation unbonded
over the roof membrane. Install
a slip or separation sheet over
the membrane if the membrane
is coal tar or Type 1 or 2 asphalt,
or if required by the membrane
manufacturer.

Butt boards tightly together
with a maximum 3/8" gap
between boards, staggering end
joints. The recommended stagger
between each board is 2'.
However, in cases where boards
have been cut to fit, try and
maximize the stagger where pos­sible. At a minimum, each board
should have at least an 8" stagger.

When using STYROFOAM
insulation with pre-cut drainage
channels, ensure that the
drainage channel edges are face
down (i.e., on the membrane side).

Bevel edges to fit closely to
cant slopes.

Fit around protrusions and
obstructions with a maximum
3/4" gap to minimize heat loss.

Multi-layer foam installation:

• The bottom layer of insulation

(the layer directly on the

membrane) must be at least

2" thick.

• The bottom layer must be the

thickest or, at minimum, equal

to the top layer (e.g., 3" bottom

and 3" top).

• Lay successive layers of

insulation unbonded or

unadhered.

• Stagger or offset all joints from

those of the underlying layer.

Installation Notes

Protect insulation from physi-

cal damage.

Handle boards carefully to pre-

vent damage during installation.

Always wear protective eye­wear and gloves when handling
and cutting insulation.

Always store insulation away
from direct sunlight, particularly
when storing for an extended
time. Cover with a light-colored
opaque tarp for protection from
solar radiation. The surface
degradation caused by ultraviolet
(UV) light will have no measurable
effect on the insulating value
unless the deterioration is
allowed to continue until actual
thickness is lost.

Always check the compatibility
with other products that may
come in direct contact with the
insulation, particularly those
containing solvents. Preventive
care must be taken, such as
allowing the solvents to evapo­rate, providing a slip sheet or
painting the surface of the insu­lation with white latex paint.
Always brush off any surface
dust before applying white latex
paint on the insulation.

STYROFOAM™extruded poly­styrene insulation is combustible
and may constitute a fire hazard
if improperly used or installed.
The insulation contains a flame­retardant additive to inhibit
ignition from small fire sources.
During shipping, storage, instal­lation and use, this material
should not be exposed to open
flames or other ignition sources.

C O M P O N E N T S – S T Y R O F O A M E x t r u d e d P o l y s t y r e n e I n s u l a t i o n

®™Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow

7