Canada COMMERCIAL Protected Membrane Roof Installation Guidelines OVERVIEW GLOSSARY COMPONENTS 2 4 6 STYROFOAM™ Brand Extruded Polystyrene Foam Insulation 6 Fabric 8 Ballast 10 Pavers 12 All Other Components CONDITIONS, 13 ISSUES AND RATINGS Special Conditions and Issues 15 15 Cold Rain Phenomenon 15 Moisture Absorption 16 Dimensional Stability 16 Vegetative Roof Design 17 Finding Leaks in a PMR 18 Low Temperature Applications 18 High Temperature Installation 19 Membrane Se
OVERVIEW Overview 2 CHANGING THE SEQUENCE Protected membrane roofing’s breakthrough contribution to 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.
CHANGING THE SEQUENCE 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 exceptional long-term performance and durability.
GLOSSARY Glossary Absorption: the ability of a material to absorb quantities of 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.
Humidity: the amount of Positive Drainage: the drainage moisture contained in the atmosphere. Generally expressed as percent relative humidity (% RH). It is the ratio of the amount of water vapour actually present in the air, compared to the maximum amount that the air could contain at the same temperature. 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.
COMPONENTS – STYROFOAM™ Brand Extruded Polystyrene Foam Insulation Components 6 S T Y R O F O A M™ B R A N D E X T R U D E D P O L Y S T Y R E N E F O A M I N S U L A T I O N Description STYROFOAM Brand Extruded Polystyrene (XPS) Foam Insulation is a rigid, closed-cell insulation, ideally suited and designed for PMR installations.
S T Y R O F O A M™ B R A N D E X T R U D E D P O L Y S T Y R E N E F O A M I N S U L A T I O N Function Provide thermal properties: STYROFOAM™ Brand Extruded Polystyrene Foam Insulation has a high aged thermal resistance (R-value or RSI) 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.
COMPONENTS – Fabric Components FABRIC Description Ballast reduction fabric, commonly known as filter fabric, is used in PMR installations between the ballast and insulation. This water-permeable material must have proven longterm weather resistance, be strong enough to withstand traffic abuse and prevent displacement of the insulation under flotation conditions. Specification Apply fabric unbonded and shingle fashion over the installed insulation (Figure 3).
COMPONENTS – Fabric Components FABRIC Extend the fabric up the roof perimeter cants and roof protrusions by at least 3" (75 mm) above the top level of the ballast (typically about a 6" [150 mm] upturn) and place it loose under the metal counterflashings (Figure 5). Fabrics, such as Fabrene V.I.E.,† should meet or exceed the guidelines listed in Table 1. For a complete list of acceptable filter fabrics, contact a Dow representative.
COMPONENTS – Ballast Components BALLAST Description Crushed stone or washed, rounded riverbed rock, with a 1" (25 mm) clear size, free of fines or stones smaller than 5/8" (15 mm) or larger than 1-3/8" (35 mm). Most stones should be 3/4" to 1-1/4" (19 mm to 32 mm) size. Function Prevent uplift and prevent flotation: Ballast is required to prevent negative flotation and is based on the total thickness of STYROFOAM™ Brand Extruded Polystyrene Foam Insulation and the type of membrane used.
BALLAST Specification Sound, hard, washed stone or gravel, freeze-thaw resistant, with a 1" (25 mm) clear size, free of fines or stones smaller than 5/8" (15 mm) or larger than 1-3/8" (35 mm). Most stones should be 3/4" to 1-1/4" (19 mm to 32 mm) size. PMR (without fabric): Spread stone ballast uniformly over installed insulation to provide minimum weight or thickness (Table 2).
COMPONENTS – Pavers Components PAVERS Description Concrete slab pavers or interlocking pavers can be used to supplement or replace conventional 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.
ALL OTHER COMPONENTS Description MEMBRANES The membrane is the flexible or semi-flexible waterproofing layer on the roof deck. In a PMR application, the membrane is sandwiched between the roof deck and the insulation. Membranes fall into three general categories: built-up roof (BUR), two-ply modified bitumen, single-ply (sheet) or liquid membranes. Note: PMR assemblies should be installed with adhered membranes only.
COMPONENTS – All Other Components Components 14 ALL OTHER COMPONENTS Function The roof deck should: • Provide structural support to accommodate both live and dead loads without significant deflection. • Provide dimensional stability by forming a stable substrate not affected adversely by cyclical thermal- and moisture-induced movement. • Provide fire resistance as determined by the building type and intended use. • Provide a substrate for the roof system. • Accommodate building movement.
SPECIAL CONDITIONS Cold Rain Phenomenon THE ISSUE “Cold rain phenomenon” (or “cold water wash”) occurs during periods of cold rain and/or melting snow or when the ambient condition is 33°F to 50°F (1°C to 10°C). In these conditions, the deck temperature may be temporarily reduced. The issue is that there may be additional heat loss, and in buildings with high humidity, such as pulp and paper mills, the likelihood of condensation increases.
C O N D I T I O N S , I S S U E S A N D R AT I N G S – S p e c i a l C o n d i t i o n s a n d I s s u e s Conditions, Issues and Ratings 16 SPECIAL CONDITIONS Moisture Absorption AND ISSUES STYROFOAM™ Brand Extruded Polystyrene Foam Insulation will absorb water and the insulation value will be reduced. Always ensure that the roof deck has proper drainage; if the PMR system has significant ponding (e.g., standing water), the insulation will not be “diffusion open.
SPECIAL CONDITIONS Vegetative Roof Design THE ISSUE Can PMR assemblies be used for vegetative roof designs? AND ISSUES Vegetation Soil System Filters Filter Fabric DISCUSSION In a “green roof” design, the ballast in a PMR assembly is essentially replaced with vegetative soil and plantings – plus a drainage layer directly on top of the insulation (Figure 6).
C O N D I T I O N S , I S S U E S A N D R AT I N G S – S p e c i a l C o n d i t i o n s a n d I s s u e s Conditions, Issues and Ratings 18 SPECIAL CONDITIONS Finding Leaks in a PMR THE ISSUE Is it more difficult to locate a leak with a PMR or conventional roof assembly? DISCUSSION Building upon years of in-field experience, the majority of roof leaks in PMR systems occur at flashing as opposed to the interior field area.
SPECIAL CONDITIONS High Temperature Installation THE ISSUE In high temperature locations, PMR assemblies should not be covered with a dark fabric prior to laying the ballast because of the potential adverse effect on the STYROFOAM™ Brand Extruded Polystyrene Foam Insulation. DISCUSSION Like many insulations, higher temperatures may cause permanent distortion and/or long-term creep.
C O N D I T I O N S , I S S U E S A N D R AT I N G S – F i r e a n d Wi n d R a t i n g s Conditions, Issues and Ratings FIRE AND WIND RATINGS Overview Fire and wind ratings are required to meet building code requirements. Typically, a PMR assembly, including roof deck, membrane, insulation and ballast, is tested in exactly the same configuration as would be constructed in the field. No deviation from the component specification is allowed. Underwriters Laboratories Inc.
FIRE AND WIND RATINGS ULI Hourly Fire Resistance Ratings for PMR – Steel Deck Assembly # Rating (hrs) Description P-225, P-226, P-235 (New PMR) 1, 1-1/2 Steel deck 1/2" or 5/8" (13 mm or 16 mm) Type X gypsum (varies) Bar joists Suspended ceiling P-404 (New PMR) 1-1/2 Steel deck 1" (25 mm) mineral or fiberboard Bar joists Plaster ceiling P-801, P-805 (Retrofit PMR) 1, 1-1/2, 2 Steel deck Mineral or fiberboards Spray fiber fireproofing Beam construction P-803 (Retrofit PMR) 1, 1-1/2 Steel de
C O N D I T I O N S , I S S U E S A N D R AT I N G S – F i r e a n d Wi n d R a t i n g s Conditions, Issues and Ratings 22 FIRE AND WIND RATINGS ULI Hourly Fire Resistance Ratings for PMR – Concrete Deck Assembly # Rating (hrs) Description P-904, P-909, P-912, P-915 (Retrofit PMR) 2 Precast concrete units Mineral fiberboard P-904, P-909, P-912, P-915 (New PMR) 2 Precast concrete units 1" (25 mm) gypsum board ULI Hourly Fire Resistance Ratings for PMR – Other Assembly # Rating (hrs) Descri
FIRE AND WIND RATINGS ULC Hourly Fire Resistance Ratings for PMR – Metal Deck Assembly # Rating (hrs) Description R-202, R-217 (New PMR) 1 Steel deck 1/2" (13 mm) gypsum Beams or bar joists Suspended ceiling R-702, R-703 (New PMR) 1, 1-1/2 Steel deck 5/8" (16 mm) gypsum Spray cementitious mixture Beams or bar joists R-804 (New PMR) 3/4, 1, 1-1/2, 2, 3 Steel deck 5/8" (16 mm) Type X gypsum Spray fiber fireproofing Beam construction R-805, R-806 (New PMR) 1 Steel deck 1/2" or 5/8" (13 mm or
For Technical Information: 1-866-583-BLUE (2583) (English) . 1-800-363-6210 (French) For Sales Information: 1-800-232-2436 (English) . 1-800-565-1255 (French) DOW CHEMICAL CANADA ULC . Dow Building Solutions . Suite 2100 . 450 – 1st St., SW . Calgary, AB T2P 5H1 www.dowpmr.com Illustrations are not intended to replace the need for design by appropriate professionals such as architects or engineers. NOTICE: No freedom from any patent owned by Dow or others is to be inferred.
