Re-roofing encompasses both primary membrane
replacement and replacement of the entire roofing assembly above
the structural deck.
Due to the unique nature of re-roofing, relief
from the Warranty Certificate standard may be requested. When
relief is requested, applications shall be made in a written
submission to the ARCA Warranty Ltd. Technical Committee. This
request for relief is termed a “Variance Request” and
must contain all pertinent information explaining why relief is
The Warranty Certificate standards, as itemized
in this manual, are applicable to re-roofing as well as new
construction, with the exception that the existing drainage slope
may be retained in a conventional membrane design if less than
Sheet metal flashings, including lead flashings,
adhered to the primary membrane shall be replaced with new
materials. Base and cap flashings may be reused provided they are
in good condition, fabricated to the Warranty Certificate standard
and fit properly.
The Warranty Certificate can only be issued on
self-contained roof areas. Control joints may be required to create
self-contained roof areas when partial roofing system replacement
is carried out. Special attention to drainage provisions may be
Roof mounted equipment may need to be removed
and reinstalled to facilitate replacement of the roofing system
beneath them. Equipment mounted on properly constructed curbs of
sufficient height may not require removal.
A minimum clearance of 100mm (4”) shall be
maintained between the underside of service lines and the surface
of the completed roofing system.
When an existing roofing systems is of a
different bitumen type than the new system to be applied (e.g. Coal
tar pitch to asphalt), care must be taken to ensure that the two
dissimilar bitumens do not come into contact with each other.
In some instances there may be two (2) roof
systems one above of the other, over an existing roof area. Where
two (2) primary membranes are present, both primary membranes shall
Prior to reroofing, all damaged or deteriorated
decks and substrates shall be replaced or repaired with similar
Existing BUR, SBS modified bituminous or hot
rubberized asphalt protected membranes may remain in place and
serve as the substrate for the attachment of a replacement modified
bitumen protected membrane design provided that the existing
membrane is prepared by removing any wet or deteriorated material,
dust, dirt and debris and primed with a compatible primer.
Existing modified bitumen flashing membranes,
when properly adhered and primed with a compatible primer, may
remain in place and serve as the substrate for the attachment of a
two (2) ply torch adhered modified bituminous membrane flashing.
Loose and deteriorated flashing membranes must be removed or
covered with an accepted membrane flashing substrate.
To qualify for an ARCA 15 Year Warranty
Certificate, only new drains shall be installed equal in size to
existing roof drains.
MB-10.2 Primary Membrane
When considering an existing conventional
insulated roofing system for primary membrane replacement the
following factors require evaluation:
The affect that the lack of a vapour retarder may have had on
the failure of the existing membrane,
The type, condition and thickness of the existing insulation
and the amount of moisture that may have infiltrated the insulation
The existing roof deck type and its structural integrity, if
moisture reached the deck, and
The attachment of roofing system components to their existing
When membrane replacement is undertaken,
uncorrected defects hidden from view, such as wet insulation or
deteriorated deck, could jeopardize roofing system
Wet and damaged insulation shall be removed and
replaced with new insulation, to match the existing
Care must be taken to ensure all wet insulation
is located and replaced.
Under no circumstance shall a phenolic resin
insulation product be left in place or reused.
Existing wood fiberboard, mineral/perlite, glass
fibre or Stramit primary insulation may be left in place whether or
not they are covered by a secondary insulation/cover board.
Existing polyisocyanurate, urethane, foamglass,
cork, expanded polystyrene, glass fiber less than 38mm (1.5”)
thick and extruded polystyrene roof insulation less than 38mm
(1.5”) thick must be removed and replaced, except when
covered by a secondary insulation/cover board consisting of wood
fiberboard or perlite insulation. Exercise extra caution to ensure
that all wet primary insulation is located and replaced when there
is a secondary insulation/cover board in place.
When the primary membrane is being
removed from stramit or glass fiber insulation that have a facer,
the condition of the insulation facer after the tear off determines
the surface preparation method for the application of the new roof
membrane. When re-roofing over stramit the first layer of approved
coverboard must be mechanically fastened to the structural joist or
deck. If the first layer is fiberboard, then the second layer of
approved 12.7mm (1/2") coverboard may be adhered or mechanically
fastened with screws and plates. When thermal upgrading is
required, the first layer of the secondary insulation/coverboard
may be substituted for/by the upgraded insulation material.
Attachment requirements remain the same.
Regardless of the primary insulation type or the
presence of an existing secondary insulation/cover board, in all
cases, a new secondary insulation/cover board layer meeting ARCA
Warranty Certificate application standards is required to provide a
consistent substrate for the application of the new roof
Polyurethane foam adhesive may NOT be used
to adhere insulation or coverboard to existing fiberglass
insulation, perlite insulation or stramit.
MB-10.3 Roofing System
After tear-off the exposed substrate shall be
inspected for deterioration or damage and repairs undertaken prior
to the application of the replacement roofing system.
Control joints, parapets, curbs and roof/wall
junctions shall be adjusted to comply with the minimum height
requirements for new construction.
For conventional and combination designs, the
application of a vapour retarder is a requirement whether or not
the original roofing system contained a vapour retarder
An existing vapour retarder may be left in place
if well adhered. Any wet or damaged membrane shall be removed and
an additional one (1) ply of felt adhered with hot bitumen shall
cover the entire membrane surface.
When primary membrane replacement occurs
over existing insulating Stramit or rigid glass fiber roof
insulation, inspection of the exposed insulation by an ARCA
Accepted Inspector is required at the time of tear off, for both
rural and urban projects. Additionally, if there is a history of
leaking, the inspector shall perform moisture meter or cut tests,
one (1) for each 1000 ft² of insulation area. These quality
assurance inspections shall be in addition to the normal
inspections required for Warranty Certificate issuance.
ARCA administration shall be notified of the
condition of structural stramit decks prior to re-roofing.