][3.5.3
Wood Decks and Other Wood Surfaces
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NOTE: Spray foam may be applied to wood decks when
the following minimum requirements are met: Wood
decks are designed and constructed for maximum
deflection of L/240 under all loading conditions,
including dead and live loads and loads from
construction or maintenance; all laminated woods
have waterproof adhesives; all plywood is at least
equal to PS-1, Exterior grade B-C, 13 mm (1/2 inch)
thick, with edge joints supported by framing. Foam
used on wood roofs should not be placed over
plank-type or tongue-and-groove wood decks unless
decks are first overlaid with 6mm (1/4 inch)
Exterior grade B-C plywood and nailed on 12 inch
centers with 4d, annular-groove nails.
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Prime untreated and unpainted surfaces.
If painted, inspect surfaces for
adhesion problems.
][3.5.4
Existing Roof Covering Surfaces
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NOTE: This specification is written for new
construction; adaptation of this system to reroofing
jobs requires preparation of the existing roof in
accordance with the spray foam roof manufacturer's
recommendations. Requirements vary based on
existing roof type. Where gravel, aggregate or
ballasted roof is present, surfacing must be removed
prior to spray foam application.
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Prepare existing roof covering systems to receive spray polyurethane foam
in accordance with recommendations of manufacturer of the spray
polyurethane foam materials.
]3.6
SPRAY FOAM APPLICATION
3.6.1
Spray Foam
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NOTE: Specify minimum thickness. This thickness
shall be the thickness required to attain the
U-factor for the complete roof construction
including insulation requirements for the design of
heating and air-conditioning systems, except that
not less than 38 mm (1-1/2 inch) thickness shall be
specified.
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Apply foam to provide a minimum finished thickness of [38 mm (1-1/2
inches][_____] inches in at least two spray passes. Apply each spray pass
at right angles to the previous pass to the extent practicable. Each pass,
except for filleting or tapering as required at terminations, shall be
between 13 mm (1/2 inch) and 25 mm (1 inch) in thickness. Check foam
SECTION 07570
Page 31
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