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MB Section 3: Separator Sheets and Auxiliary Leveling Surfaces

MB-3.1 Separator Sheets

MB-3.1.1 General

.1

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

MB-3.1.2 Wood Decks

MB-3.1.2.1 Uninsulated Systems

.1

Direct application of hot bitumen to wood decks is not permitted. Glass coated base sheet or fire resistant approved underlayment must be installed on all wood decks when a modified bituminous membrane is mechanically fastened. There can be no exposed fasteners.
Revised

2016-01

.2

Follow the membrane manufacturer's application recommendations when mechanically fastening the screws and plates.
Revised

2016-01

MB-3.1.2.2 Insulated Systems

.1

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

MB-3.1.3 Concrete Decks

MB-3.1.3.1 Cast-In-Place Concrete Decks

.1

Separator sheets are not required over cast-in place decks.

.2

Priming of the concrete surface with an asphalt primer is optional.

MB-3.1.3.2 Precast Concrete Decks

.1

A separator is not required when adhering modified bituminous membranes directly to precast concrete decks with hot bitumen, except at deck joints.

.2

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 or modified bituminous base sheet shall continuously cover the grouted deck joints.

.3

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 or a compatible SBS adhesive.

MB-3.1.4 Steel Decks

.1

Hot bitumen shall not be used to adhered modified bituminous membranes directly to steel decks.

.2

Separator sheets are not required over steel decks.

MB-3.2 Auxiliary Leveling Surfaces

MB-3.2.1 General

.1

An auxiliary leveling surface is a material used to provide a smooth substrate to which roofing system components can be adhered.

.2

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 Glass Mat Gypsum Substrate (ASTM C1396), 12.7mm (1/2") thick plywood, or 12.7mm (1/2") thick O.S.B. when not used as a thermal barrier.
Revised

2017-04

.3

The existing substrate type and condition will determine the auxiliary leveling surface type and attachment method.

.4

Where required by the Alberta Building Code, a thermal barrier may be used as an auxiliary leveling surface.

MB-3.2.2 Wood Decks

.1

For dimensioned lumber decks an accepted auxiliary leveling surface shall be mechanically fastened to completely cover the lumber decking. Hot bitumen shall not be used to adhere directly to dimensioned lumber deck.

.2

When using roofing nails for attachment, use a minimum of one (1) nail per square foot of surface area.

.3

When using drywall screws for attachment, use a minimum of twenty (20) per 1200mm x 2400mm (4’ x 8’) sheet.
Revised

2016-06

.4

When using screws and plates for attachment, use a minimum of eight (8) per 1200mmx2400mm (4’ x 8’) sheet.
Revised

2016-06

.5

Mechanical fasteners (nails or screws) must be of sufficient length to penetrate a sheathing material by a minimum of 12.7mm (½") beyond the lower surface and a minimum of 25mm (1") into dimensioned lumber.

MB-3.2.3 Steel Decks

.1

For uninsulated and protected membrane designs an accepted auxiliary leveling surface (excluding perlite and wood fiber boards) shall completely cover the steel decking prior to membrane application. SBS modified bituminous membranes shall not be applied directly to steel decks except as a vapour retarder.

.2

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 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’ x 8’) 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

.3

To qualify for an ARCA 15 Year Warranty Certificate, a minimum 12.7mm (1/2”) glass faced gypsum auxiliary leveling surface shall be mechanically fastened to the structural deck.
Added

2016-08

MB-3.2.4 Concrete Decks

.1

An auxiliary leveling surface is not required over concrete decks.

.2

Damaged and deteriorated concrete decks shall be repaired to provide a smooth substrate for roofing system application.