BUR Section 3: Separator Sheets And Auxiliary Leveling Surfaces

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Separator sheets are materials used to separate roofing system components, to prevent material incompatibility or to prevent adhesion.

A separator shall completely cover wood decks, as hot bitumen is not accepted for adhering BUR membranes directly to wood decks for Warranty Certificate issuance.
For organic felt membranes, a separator comprised of two (2) plies of No. 15 organic felt or one (1) ply of a coated base sheet shall be nailed to the wood decking.
For fiberglass felt membranes, a separator consisting of one (1) ply Kraft laminate nailed plus one (1) ply fiberglass felt nailed is required.
Attach separator sheets using galvanized roofing nails spaced at 150mm (6”) centres along the sheet edges and 300mm (12”) centres throughout the field of the separator sheet.
For O.S.B. and plywood sheathing decks, the nails shall be long enough to extend a minimum distance of 12.7mm (1/2”) beyond the lower surface of the decking.
For dimensional lumber decks, the nails shall penetrate a minimum distance of 25mm (1”) into the wood decking.

For conventional insulated BUR roofing systems over wood decks, the vapour retarder membrane will serve as the separator sheet.

A separator is not required when adhering BUR membranes directly to cast-in-place concrete decks with hot bitumen.
Hot bitumen may be used to adhere membranes to concrete decks. Priming of the concrete surface with an asphalt primer to improve adhesion is optional.

A separator is not required when adhering BUR membranes directly to precast concrete decks with hot bitumen except at deck joints.
Where joints between precast concrete deck sections are grout filled, a separator sheet shall cover joints. Installed dry, a 150mm (6”) wide strip of coated base sheet shall continuously cover the grouted deck joints.
When precast deck sections do not contain grout keys, continuously cover joints by installing a one half (1/2) roll minimum 457mm (18”), width strip of a coated base sheet. Adhere one side of the separator sheet to within 150mm (6”) of the deck joint centre line with asphalt.

Hot bitumen cannot be used to adhered BUR membranes directly to steel decks.
An auxiliary leveling surface is required in place of a separator sheet for uninsulated systems.

An auxiliary leveling surface is a material used to provide a smooth substrate to which roofing system components can be adhered.
ARCA accepted auxiliary leveling surfaces may be comprised of a minimum 9.5mm (3/8″) thick Fibre Reinforced Gypsum Panel (ASTM 1278), 12.7mm (1/2″) thick Glass Mat Gypsum Substrate (ASTM 1177), 12.7mm (1/2″) thick Gypsum Board (ASTM C1396), 12.7mm (1/2″) Fibre-Mat Reinforced Cementitious Board (ASTM 1325), 12.7mm (1/2″) thick plywood, or 12.7mm (1/2″) thick O.S.B. when not used as a thermal barrier.
*REVISED 2019-04
The existing substrate type and condition will determine the auxiliary leveling surface type and attachment method.
Where required by the Alberta Building Code, a thermal barrier may be used as an auxiliary leveling surface.

For dimensioned lumber decks an accepted auxiliary leveling surface shall be mechanically fastened to completely cover the lumber decking, as BUR membranes cannot be adhered directly to wood decks with hot bitumen.
For uninsulated four (4) ply BUR primary membrane systems over wood sheathing decks, a minimum 12.7mm (1/2”) thick fiberboard or gypsum board auxiliary leveling surface shall be mechanically fastened to the O.S.B. or plywood decking.
When using roofing nails for attachment, use a minimum of one (1) nail per square foot of surface area.
When using drywall screws for attachment, use a minimum of twenty (20) per 1200mm x 2400mm (4’x8’) sheet or a minimum six (6) screws for 600mm x 1200mm (2’x4’) sheets.
Follow Factory Mutual (FM) requirements when using screws and plates.

For uninsulated and protected membrane designs an accepted auxiliary leveling surface shall completely cover the steel decking prior to membrane application, as BUR membranes cannot be adhered directly to steel decks with hot bitumen.
The auxiliary leveling surface may be attached to the steel decking using one of the following attachment methods:
1. Continuous beads or a full roller coating of an acceptable adhesive applied to the top flanges of the steel deck in accordance with the adhesive manufacturer’s application rates.
2. Minimum twenty (20) self tapping drywall screws per 1200mm x 2400mm (4’x8’) sheet fastened through the top flange of the steel decking. Where drywall screws break the gypsum board paper covering, install a replacement screw in approximately the same location. Additional fasteners may be required to meet wind uplift standards.
  *REVISED 2016-04
3. When using screws and plates for attachment, use a minimum of eight (8) per 1200mmx2400mm (4’ x 8’) sheet fastened through the top flange of the steel decking. Additional fasteners may be required to meet wind uplift standards
  CAUTION:
  Attachment method (b) for steel deck is experienced based. ARCA has not conducted formal wind studies.
  *REVISED 2016-04

An auxiliary leveling surface is not required over concrete decks as BUR membranes may be adhered directly to concrete decks with hot asphalt.
Damaged and deteriorated concrete decks shall be repaired to provide a smooth substrate for roofing system application.