SBS Modified Bitumen - Page 11

C. Non-Nailable Decks, other than Steel:

1. Prepare the deck as would be done for a permanent roof.

2. Solid mop two plies of approved JM ply felt in hot Type III asphalt.

3. Finish with a 10 - 15 lbs. per square (0.49 - 0.73 kg/m²) glaze coat of Type III asphalt.

4. When the permanent roof is to be installed, inspect and repair all defects in the temporary roof. Clean the surface of the temporary roof and prime with JM Concrete Primer if the surface is unusually worn. Proceed with the installation of the permanent roof.

5. As an alternate to step 2, spot mop an approved JM base sheet using a mechanical spot mopping machine. Next, solid mop one ply of approved JM ply felt in hot Type III asphalt. When the permanent roof is to be installed, remove the entire temporary roof, prime the deck as required in the "Roof Decks" Section of this manual, and proceed with the installation of the permanent roof.

7A.32.3 The decision as to whether or not a temporary roof is to be left in place is a judgment factor that must be made by the building owner or his representative. Although a JM representative may make suggestions in this area, JM will not be responsible for any problems that may develop with the roofing system due to the fact that the temporary roof is left in place.

7A.33 Protected Roofing Membrane Assemblies (PRMA)

7A.33.1 General Information. All general information contained in this section and the current JM Commercial/Industrial Roofing Systems Manual shall be considered part of these specifications.  JM modified bitumen specifications are eligible for use with protected roofing membrane assemblies. When these specifications are modified, the last digit of the specification designation should be changed to a "P" to denote "Protected".

Flashings: All flashings must conform to the requirements stated in this section and the current JM Commercial/ Industrial Roofing Systems Manual. The flashing material must extend above the top of the extruded polystyrene insulation a minimum of 8" (203 mm). The standard flashing details for modified bitumen roofing can be found in "Bituminous Flashings", Section 8.

Drainage: Design and installation of the deck and/or roof substrate must result in the roof draining freely, to outlets numerous enough and so located as to remove water promptly and completely. Areas where water ponds for more than 24 hours are unacceptable, and will not be eligible for a JM Roofing System Guarantee.

7A.33.2 When designing a protected membrane roofing system, the designer must make sure that positive drainage exists on the roof. Even though some extruded polystyrene roof insulation products are designed with integral drainage channels, they will retard the flow of water due to the contact between the membrane and the insulation. JM recommends a minimum of 1/4" per foot (20.8 mm/m) slope be obtained on the finished roof membrane. This will greatly reduce the amount of water that will be retained against the membrane after a rain.

7A.34 Asphalt Recommendations (PRMA)

7A.34.1 JM allows the use of only two grades of asphalt in SBS modified bitumen specifications – Type III and Type IV. This recommendation also applies to PRMA specifications, in order to prevent adhesion of the extruded polystyrene insulation to the asphalt top pour.

7A.34.2 Ballast Requirements (for use with extruded polystyrene roof insulation):

7A.34.3 The ballast should be similar to ASTM D 448, Gradation #57.

The following gradation is typical:

Passing 1/2" (13 mm) 10-60%

Passing 3/4" (19 mm) 100%

7A.34.4 Ballast is applied at a rate of approximately 10 to 12 lbs. per square foot (48.8 - 58.6 kg/m² ) in the field of the roof over a layer of filter fabric. Twenty (20) lbs. per square foot (97.6 kg/m²) of ballast is required over a 4' (1.22 m) wide area at the roof perimeter and at all penetrations. The following fabrics have been found to be acceptable:

A. Confil 689H – 3.0 oz./yd. (93.5 g/m) black polyester from International Paper Company.

B. Rufon P3B – 3.0 oz./yd. (93.5 g/m) black polypropylene from Phillips Fiber Corporation.

7A.34.5 JM makes no claims as to the quality of these products nor their performance when exposed on the roof. See the product warranty supplied by the fabric manufacturer.

7A.34.6 When pavers are used as ballast, the pavers must be placed on supports or pedestals. These supports or pedestals can either be commercially available products or 6" (152 mm) square pieces of JM DynaTred Plus (to give a minimum 1/2" [13 mm] air space). These supports should be located at the intersection of the corners of the paver blocks, such that where the four corners come together, all rest on the same 6" (152 mm) square piece of DynaTred Plus or pedestal. The 1/2" (13 mm) air space between the pavers and the insulation will allow moisture vapor to vent to the atmosphere. If the moisture is not allowed to vent to the atmosphere, the top surface of the insulation will begin to absorb water and the thermal performance will be reduced. ROOF AREAS THAT HAVE PAVERS IN DIRECT CONTACT WITH THE INSULATION ARE EXCLUDED FROM COVERAGE UNDER A JOHNS MANVILLE ROOFING SYSTEM GUARANTEE, INCLUDING THE THERMAL OVERLAY PORTION OF THE GUARANTEE.

7A.34.7 The use of pavers in high traffic areas, to and around equipment and other maintenance areas, is strongly recommended.

7A.34.8 It is the owner’s and/or specifier’s responsibility to determine if the building structure can support the required amount of ballast and still meet the code design requirements for anticipated dead and live loads (including snow, wind, etc.).