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Serving Alberta's Roofing Industry Since 1961
TP Section 1: Roof Decks
The roof deck provides the structural support
for the roofing system. Roof decks shall be designed in accordance
with the Alberta Building Code to support design and construction
The surface of roof decks must be sufficiently
clean, dry and sound to receive roofing materials, so proper
adhesion and attachment may take place.
Where electrical conduits, fittings, bolts and
plates project above the deck surface, a smooth substrate plane
shall be provided to receive roofing materials. Correction to the
substrate plane in the proximity of the projections must be
addressed on an individual project basis.
Roof deck perimeters shall be structurally
supported. Deck openings require additional structural framing to
support and to prevent excess deflection of the surrounding
For mechanically attached membranes, the roof
deck type, thickness and structural attachment must comply with the
membrane manufacturer's requirements for minimum fastener pull out
values and fastener density.
TP-1.2 Wood Decks
TP-1.2.1 Dimensioned Lumber Decks
Dimensioned lumber decks may be constructed from
sawn lumber, planks or ship lapped boards.
For uninsulated and protected membrane design
thermoplastic roofing systems, a mechanically fastened auxiliary
leveling surface must completely cover dimensioned lumber
TP-1.2.2 Sheathing Decks
Plywood and oriented strand board (O.S.B.)
sheathing shall be manufactured for exterior application.
Fully adhered and mechanically attached
thermoplastic systems may be installed directly to minimum 15.9mm
(5/8") thick plywood or O.S.B. sheathing provided that the decking
is secured with screws and plates as nailing is not
TP-1.3 Concrete Decks
Cast-in-place and pre-cast concrete decks shall
have a smooth dry surface and shall be adequately cured prior to
Pre-cast concrete deck grout keys shall be grout
The maximum differential height permitted
without correction between pre-cast concrete deck members is 6.4mm
(1/4"). Height differences greater than 6.4mm (1/4") but no larger
than 19.0mm (3/4") shall be corrected using cementitious grout or
fill feathered to a maximum slope of 1:50 (1/4"/ft.). When height
differences exceed 19.0mm (3/4"), a topping coat shall be applied
to correct the deck surface.
Above deck projections such as anchor bolts and
plates shall be feather grouted to provide a smooth roofing
TP-1.4 Steel Decks
Steel deck flutes shall be reasonably free of
snow, ice and debris, prior to thermoplastic roofing
Unsupported deck openings are restricted to a
maximum dimension of 200mm (8").
TP-1.5 Stramit Decks
Stramit is a structural and/or insulating panel
manufactured from straw fibre in 50mm (2") or 64mm (21/2")
thickness as roof deck and/or insulation.
Prior to re-roofing over stramit decks, ARCA
Administration must be notified of the existing structural
condition of the stramit decking.
Stramit decks do not qualify for an ARCA
15 Year Warranty Certificate.
TP-1.6 Deck Fills
Water based cementitious insulating fills
comprised of mixtures of cement/gypsum and insulation/vermiculite
are not accepted decks for Warranty Certificate issuance.
Bituminous deck fills comprised of bitumen and
vermiculite are accepted for Warranty Certificate issuance when
completely covered with an approved separator sheet or auxiliary
The finished surface of bituminous deck fills
shall be smooth and uniform.
© 2016 Alberta Roofing Contractors Association