Template:BUR Membranes
Template:BUR Membranes
1 General
While the roof is being applied, all membrane openings at eaves, walls, vents, etc. must be sealed to prevent moisture from entering roofing or between plies of stripping.
1.1 Slope Limitations
When specifying or installing a BUR system employing modified bitumen membranes, only factory cap sheets are to be used on slopes exceeding 1:24 (1/2" in 12"). Manufacturers published instructions as to application methods, materials, and slope limitations are to be followed. On slopes less than 1:24 (1/2" in 12"), double pour, modified double pour or alternate modified double pour and gravel surfacing may be used.
1.2 Roof Slope and Roof Surfacing
The maximum slope for a graveled built-up roof is 1:5 (2-1/2" in 12"). Where roof slopes exceed 1:12 (1" in 12"), back-nail mopped sheet at 600 mm (2' 0") using large-headed roofing nails. On insulated roofs, install nailing strips to facilitate back-nailing. A double pour, modified double pour, or alternate modified double pour is to be applied on slopes up to 1:24 (1/2" in 12"). For slopes exceeding 1:24 (1/2" in 12") but not exceeding 1:5 (2-1/2" in 12"), use a single pour and gravel.
A single pour and gravel surfacing is defined as a minimum of 3 kg / m² (60 lb / square) of asphalt and 20 kg / m² (400 lb / square) of suitable roofing gravel.
A double pour and gravel is defined as a minimum of 3 kg / m² (60 lb / square) of asphalt in each pour coat and 20 kg / m² (400 lb / square) of gravel for each gravel application.
A modified double pour and gravel is defined as 2 kg / m² (40 lb / square) of asphalt in the first pour followed by a 10 kg / m² (200 lb / square) gravel application, then a 3 kg / m² (60 lb / square) pour coat of asphalt followed by a 20 kg / m² (400 lb / square) second application of gravel.
An alternate method of a modified double pour and gravel is defined as 2 kg / m² (40 lb / square) of asphalt flood coat followed by an additional 3 kg / m² (60 lb / square) pour coat of asphalt followed by a 25 kg / m² (500 lb / square) application of gravel.
1.3 Membrane Lap Preparation
- Granules are to be embedded prior to forming laps on all torch applied modified bituminous cap sheets.
- Membrane end lap corners must be cut on a bias (clipped or trimmed on an angle) prior to forming laps on all torch applied modified bituminous membrane roof systems.
2 Material Selection
See Accepted BUR Membrane Components and Systems for RoofStar Guaranteed roof systems. See also Section 4 for special requirements concerning Membrane Roof Systems.
2.1 Bitumen (Asphalt) Requirements
For slopes up to 1:12 (1" in 12") use Type 2 asphalt. For slopes over 1:12 (1" in 12") but not exceeding 1:4 (3" in 12"), use minimum Type 3 asphalt.
Use asphalt quantities of approximately 1 kg / m² (20 lb / square) for each mopping and approximately 3 kg / m² (60 lb / square) for the pour coat.
For hot asphalt adhered modified bitumen roofing membranes
- It is essential that the asphalt temperature be no lower than 205°C (400°F) on the rooftop, and that maximum mopping distance from the roll not exceed 1 m (3'). A wave of liquid asphalt must be visible in front of the roll as it is being applied.
- For all applications other than protected membrane applications, the use of Type 3 asphalt is mandatory, unless the membrane manufacturer specifies a higher grade.
- For protected and modified protected membrane systems, use Type 2 or Type 3 asphalt for slopes up to 1:24 (1/2" in 12"). For slopes of 1:24 (1/2" in 12") to 1:4 (3" in 12"), use Type 3 asphalt only, unless the membrane manufacturer specifies a higher grade.
2.2 Gravel
Gravel for BUR application shall be clean, washed, round or crushed stone, opaque to ultraviolet light, and falling within the following gradations:
| Grade (mm) | Grade (in.) | Percent Passing |
|---|---|---|
| 20 | ¾ | 100 |
| 12.5 | ½ | 85 - 100 |
| 6.3 | ¼ | 0 - 35 |
| 2.5 | #8 | 0 - 5 |
| 1.25 | #1 | 0 - 3 |
| 0.075 | #200 | 0 - 1.5 |
Any variance to the above must be accepted by the owner or the owner's representative.
3 Application
3.1 Wood Decks
Direct torch (open flame) to wood surfaces is NOT permitted (i.e., when applying 'mop/torch' BUR membrane systems). All wood surfaces, decks, walls, blocking, cants, etc., MUST be protected from torch (open flame) by an acceptable separation or overlay material. Acceptable options include:
.1 RoofStar-accepted self-adhered and cold adhesive applied membranes - install over wood surfaces to manufacturers' product installation specifications. Self-adhered membranes must not be installed on contaminated wood surfaces. A minimum 9.5 mm (3/8") nominal thick plywood sheeting (overlay) must be installed over all contaminated wood surface (eg. asphalt) to receive self-adhered membranes. Metal wall base flashing is optional with these application methods.
A reverse lap application method for base sheet and base sheet flashing (stripping), at roof up stand transitions, is permitted when self-adhered base sheet flashing is used as flame protection for wood surfaces. Use of the reverse lap method must be an acceptable application method to the membrane manufacturer. The self-adhered base sheet must extend a minimum of 150 mm (6") onto the roof surface. The heat welded field membrane must be turned up at the vertical surface a minimum of 100 mm (4") or a heat welded base sheet transition gusset extending 100 mm (4") onto the roof and upstand surfaces be installed.
.2 Mechanically Attached Base Sheet - Cover wood surfaces with a minimum 40-lb asphalt-coated fibreglass base sheet conforming to CAN / CSA – A123.16 – M88 (R1996), Type II or manufacturers' accepted base sheets of equal or greater weight and reinforcement. Attachment of base sheets shall be a minimum of one nail, with a minimum 25mm (1") nominal head size, per 0.093 m2 (1 sq. ft.), or one plate and screw per 0.186 m2 (2 sq. ft). Lap base sheet end laps minimum 150 mm (6"), mechanically fix laps at 100 mm (4") o/c and seal all corner details with membrane manufacturers’ approved self-adhered SBS membrane or tape. Wood surfaces must be “dry mop” dry, no pooling or standing water permitted. Metal base flashing is required on all vertical surfaces, walls, curbs, etc., that are 200 mm (8") or greater in height above the finished roof surface, when the mechanically attached base sheet method is used.
.3 RoofStar-accepted asphalt core overlay boards (minimum thickness 4.5 mm (3/16") nominal) or insulation and insulation overlay boards specifically designed for torch applications - mechanically attach with nails with a minimum 25 mm (1") nominal head size placed a minimum of one nail per 0.093 m² (1 sq. ft.) or plates and screws placed a minimum of 0.186 m² (2 sq. ft.). Seal all board joints and wall transitions with membrane manufacturer’s approved self-adhered membrane or tapes. Alternatively a mechanically attached minimum 25-lb asphalt coated fibreglass base sheet conforming to CAN / CSA – A123.16 – M88 (R1996), Type II or 30-lb non-perforated felt conforming to CSA A123.3-M may be used prior to installing asphalt core overlay boards on wood decks. Metal wall base flashing is optional with these application methods. Wood surfaces must be “dry mop” dry, no pooling or standing water permitted.
.4 Hot Asphalt Adhered - Install modified bituminous stripping (flashing) membranes to manufacturers’ installation specifications with conventional Type 3 or 4 oxidized asphalt or Type 3 or 4 SEBS modified asphalt. Metal base flashing is required on all vertical surfaces, walls, curbs, etc. when hot asphalt is used to adhere stripping (flashing) membranes.
3.2 Gravel / Glaze
All felt roofs should be gravelled-off by the end of each working day. All installed organic, glass, or polyester felt roofing over which surfacing has not been completed must be protected with a glaze coat of bitumen, regardless of the season.
3.3 Cold Weather
In cold weather regions, membrane selection must conform to the membrane manufacturer’s recommendations for January in service design temperature.
3.4 Single-Ply Modified Bituminous Membranes
Membranes used for a single ply modified bituminous membrane system adhered or mechanically fastened shall be a minimum thickness of 3.5 mm on the selvage edge, with a minimum 150 g / meters squared polyester or equal strength polyester-fibreglass combination reinforcement.
Torch applied membrane applications require a deck separation sheet of a minimum 40-lb asphalt coated glass base sheet or torchable overlay board. Direct torch application to wood surfaces is not permitted.
A minimum slope 1:15 (¾" in 12") is required. Any roof areas less than 1:15 (¾" in 12") require 2 ply membrane assemblies.At roof slope transitions locations where slopes of less than 1:15 (¾" in 12") meet steeper slopes a two ply membrane assembly must be carried 900 mm (36") beyond the lower sloped roof transition point.
Membrane gussets must be installed to all inside and outside corners.
Modified Bituminous Base Sheet pre-stripping ply required at all perimeters, upstands and penetrations. Direct torch application to wood surfaces is not permitted.
Cap sheet stripping is required and must extend 150 mm (6") horizontally and 200 mm (8") vertically from the base of all upstands.
All stripping terminating on vertical surfaces must be mechanically fastened.
3.5 Mechanically Attached
On all adhered flexible membrane roof slopes that exceed 1:24 (½" in 12"), the manufacturer's published instructions are to be followed regarding mechanical fastening and/or back nailing of sheets, and the size and direction of sheet application to the direction of roof slope.
When applicable, all mechanically fastened flexible membrane systems installed under RoofStar Guarantee shall conform to the CSA A123.21 Standard test method (latest edition) for the dynamic wind uplift resistance of mechanically attached membrane roofing systems.
Mechanically Attached Base Sheet
Cover wood surfaces with a minimum 40-lb asphalt coated fibreglass base sheet conforming to CAN / CSA – A123.16 – M88 (R1996), Type II or manufacturers’ accepted base sheets of equal or greater weight and reinforcement. Attachment of base sheets shall be a minimum of one nail, with a minimum 25mm (1") nominal head size, per 0.093 m2 (1 sq. ft.), or one plate and screw per 0.186 m2 (2 sq. ft). Lap base sheet end laps minimum 150 mm (6"), mechanically fix laps at 100 mm (4") o/c and seal all corner details with membrane manufacturers’ approved self adhered SBS membrane or tape. Wood surfaces must be “dry mop” dry, no pooling or standing water permitted. Metal base flashing is required on all vertical surfaces, walls, curbs, etc., that are 200 mm (8") or greater in height above the finished roof surface, when the mechanically attached base sheet method is used.
3.6 Cold-Applied and Self-Adhered Membranes
When the base sheet and cap sheet membrane assemblies are self-adhered or applied using a cold adhesive, the cap sheet membrane must be installed on a clean, dry base. Therefore, barring extreme circumstances, and to comply with the manufacturer’s requirements, the base and cap sheets must be installed and completed together on the same work day. This standard does not apply where torch-applied cap membranes will be bonded to a self-adhering base membrane. Specifications and manufacturers’ written application instructions must be strictly followed. Phased installation of membranes is not permitted.
RoofStar-accepted self-adhered membranes must be installed over wood surfaces to manufacturers’ product installation specifications. Self-adhered membranes must not be installed on contaminated wood surfaces. A minimum 9.5 mm (⅜") nominal thick plywood sheeting (overlay) must be installed over all contaminated wood surface (eg. asphalt) to receive self-adhered membranes. Metal wall base flashing is optional with these application methods.
Self-adhesive membranes must only be installed when ambient temperature meets or exceeds the manufacturer’s printed product installation temperatures. All self-adhesive field membranes must be fully rolled with a manufacturer’s accepted roller that is a minimum 34.2 kg (75 lbs.) or greater and provides an evenly dispersed weight. All flashing (stripping) membrane must be hand rolled with a membrane manufacturer’s accepted roller.
The RoofStar Guarantee Program accepts cold adhesive applied membranes installed over wood surfaces to manufacturers’ product installation specifications.
3.7 Flood Testing
4 Protected and Modified Protected Membranes
| NOTE: See more information on Protected and Modified Protected Roof Systems in Section B: Essential Elements. |
4.1 General
In a Protected Membrane Roof assembly (PMR) the membrane functions solely as the waterproofing agent (the requirement for a vapour retarder is eliminated) and the properties of the insulation become more critical. Extruded expanded polystyrene (conforming to CAN / CGSB-51.20-M87, Type 4) is the only commercially produced roof insulation suitable for a PMR, providing properties such as water resistance (i.e. resistance to water absorption, moisture transfer, and capillary action), resistance to freeze-thaw cycling, and high compressive strength.
A Modified Protected Membrane Roof (MPMR) assembly is similar to a PMR except that a layer of insulation is installed underneath the membrane as well as overtop. This may offer cost savings as only the top layer of insulation requires ballast and the bottom layer (mechanically-fastened or adhered) need not be extruded expanded polystyrene and may be tapered to provide slope. The membrane must be located such that the dew point temperature (for the inside air) occurs above the membrane. As a general rule, two-thirds or more of the total thermal resistance (RSI or R value) should be above the membrane, but in all cases the design authority should perform the required psychrometric calculations before designing a roof system.
4.2 Roof Decks and Drainage
All roof decks should have proper drainage of the membrane. The RoofStar Guarantee Program recommends the deck have a minimum slope of 1:50 (¼" in 12") towards the roof drains. If, however, an existing roof allows ponding, the insulation is to be applied loose with a permeable fabric over the insulation.
Roof drains are to be located at the low points in the roof. Stone ballast must be prevented from entering drains and gutters. Perforated collars and paving stones are common methods used.
4.3 Membranes
Pour coat on all protected built-up roof membranes is to be 3 kg / meter squared (60 lb / square). Protected or modified protected roofs are to be constructed with non-organic membranes only.
Membrane flashings to be extended well above the expected high water level. Refer to the Perimeter Flashing: Membranes section in these Standards for details.
Materials used in the roof assembly must be listed as accepted in the Accepted Materials section of this Manual and conform to applicable material standards CGSB, ULL, CSA, etc.
The roof system must be designed to meet applicable building codes. This may require that 12.7 mm (½") thick gypsum board with siliconzied core and fibreglass facers or equivalent be installed on steel decks. Concrete decks do not require a separate barrier.
4.4 Insulation & Filter Mats
Insulation, which is bonded or mopped directly to the roof membrane, is not acceptable.
On all protected and modified protected membrane roofing projects, a filter mat of approved material is to be properly installed between gravel ballast and insulation. The filter mat is required under pre-cast pavers that are used as ballast or walkways.
Filter mats specified must meet the insulation / membrane manufacturer's specifications.
The use of fabric filter mat allows for the use of less ballast. This is achieved by using water permeable fabric between the loose laid insulation boards and the stone ballast. The effect of the fabric is to prevent the displacement of individual boards in case of flotation. The fabric will also prevent fines in the stone ballast from entering the board joints. The fabric must be water permeable and have proven long term weather resistance. It should be strong enough to withstand traffic abuse and prevent displacement of the boards under flotation conditions. The fabric is applied unbonded over the installed insulation. Overlap all edges a minimum of 300mm (12"). If a small piece of fabric is to be used, its dimension shall be at least 2.5 m x 2.5 m (8’ x 8’). Slit fabric to fit over roof penetrations, cut out around roof drains and other openings. Extend fabric up roof perimeter cants and roof protrusions and place it loose under the metal counter flashings.
4.5 Ballast
The building structure must be designed to support the weight of the ballast or surface treatment and other superimposed loads on the roof.
Concrete ballast, poured-in-place concrete or concrete topping as ballast or traffic topping is not permitted on RoofStar-guaranteed roofs. Only ballast, which permits easy or reasonable access to the membrane, is acceptable.
Acceptable ballast includes: properly sized gravel, concrete pavers, concrete-topped insulation, etc.
- Gravel Ballast: Protected Membrane and Ballasted Membrane (EPDM, TPO, PVC, etc.) Shall be clean, washed, round or crushed stone, falling within the following gradations:
- 35 mm (1 ½") - 100 % Passing 25 mm (1") 70 - 100 % Passing 20 mm (¾") 5 - 20 % Passing 12.5 mm (½") 0 - 6 % Passing 5 mm (3/16") 0 - 2 % Passing
- Any variance to the above must be accepted by the owner or the owner's representative and be confirmed in writing.
- Pedestals: Installation of proprietary (purpose-made) pedestals, with integral spacer ribs for uniform spacing of pavers, or an accepted drainage layer designed to provide vertical separation between pre-cast pavers and substrate or other underlying materials, is mandatory. The use of proprietary drainage boards or pea gravel with filter fabric to provide drainage for unit masonry products (bricks, stone, etc.), is required.
Proprietary (purpose-made) pedestals must have a 3mm (⅛”) integral spacer ribs for uniform spacing between pavers that provide a minimum 12.5 mm (½″) of vertical separation layer for airflow and leveling. The choice of pedestal or drainage layer type is the responsibility of the design authority. Pedestals / drainage layers provide airflow for drying surfaces and assist in leveling. They should not impede the flow of water or air, and should uniformly distribute the dead load of pavers, and other unit masonry products, as well as predicted live loads.
| Extruded Polystyrene Insulation Thickness | Required Weight of Stone Ballast | Approximate Depth of Ballast |
|---|---|---|
| Standard Measurements | ||
| Up to 2" | 12 lb./ sq. ft | 1 ¾" |
| 3" | 17 lb./ sq. ft | 2 ¼" |
| 4" | 22 lb./ sq. ft | 3" |
| 5" | 27 lb./ sq. ft | 3 ½" |
| 6" | 32 lb./ sq. ft | 4 ¼" |
| 7" | 37 lb./ sq. ft | 5" |
| 8" | 42 lb./ sq. ft | 5 ½" |
| Metric Measurements | ||
| Up to 50 mm | 60 kg / m2 | 40 mm |
| 75 mm | 84 kg / m2 | 60 mm |
| 100 mm | 108 kg / m2 | 75 mm |
| 125 mm | 132 kg / m2 | 90 mm |
| 150 mm | 156 kg / m2 | 105 mm |
| 175 mm | 180 kg / m2 | 125 mm |
| 200 mm | 204 kg / m2 | 140 mm |
Resistance to Wind Loads
Roof corners subject to high winds or gusts may scour the stone ballast. Parapets and / or paving slabs can be used where necessary to prevent scouring. In the case of a lightweight PMR roof, with insulation loose applied over the membrane and covered with 50 kg / m2 (10 lb. / sq. ft.) of ballast, external pressures due to wind are mostly applied to the membrane.
The membrane will withstand the National Building Code calculated pressure if it is properly attached to the deck. In the case of a loose applied membrane it is important to prevent any air infiltration underneath the membrane. Indeed, when air infiltration is restricted, any movement of the membrane will create a vacuum which will neutralize the uplift forces and keep the membrane on the deck.
Tunnel tests done at the National Research Council Canada show that the suction applied to the insulation boards is much lower than the calculated pressure applied to the membrane because of the rapid pressure equalization between the top and the bottom surfaces of the boards. This reduced pressure is insufficient to uplift insulation covered with 50 kg / m2 (10 lb. / sq. ft.) of ballast.