Template:PERIMETER FLASHINGS - MEMBRANES (BUR)

1 General

Membrane flashing (stripping) details (with the exception of low parapets, cant strip edges and RoofStar-accepted door sill details) must be designed to provide a minimum 200 mm (8") sealed height above the finished roof surfacing. Surfacing is defined as the top of the roofing assembly, be it membrane, ballast or growing medium (soil). All membrane flashing (stripping) terminating on a vertical surface must be mechanically fastened.

If no published instructions are available, specific instructions in writing from the manufacturer must be obtained and filed with the RoofStar Guarantee Program before project start-up.

The roof system must be designed in keeping with assemblies tested to and compliant with CSA A123.21 (latest edition), and include a calculation for the building wind load requirements using the Wind-RCI calculator.

2 Material Selection

See Accepted BUR Materials for RoofStar Guaranteed roof systems.

3 Application

3.1 Vertical Surface Application and Termination

There is no minimum height requirement for exterior walls, (e.g. eave drip and gravel stop flashing)

All stripping terminating on vertical surfaces must be mechanically fastened. Fasteners shall be installed to suit/match vertical structural supports but shall be placed no more than 24” o/c.

All membrane flashing (stripping) terminating at cladded (i.e. stucco, siding, etc.) walls must lap under the sheathing membrane and cladding by minimum of 75 mm (3").

All membrane flashing (stripping) terminating under a reglet must be sealed to the wall with a compatible mastic (see D1.7.9 Counter-flashings & Reglets (Deck - Wall Supported) et al).

3.2 Liquid Membranes

Liquid membrane flashing systems are manufactured from various bituminous and non-bituminous materials. These manufactured proprietary flashing systems are specifically designed for use to flash unusual roof penetration shapes or roof details that are difficult to flash with traditional membranes.

Liquid membrane flashings are available as one or two part component systems that require reinforcement scrims for strength. To ensure quality installation, manufacturers’ proprietary application instructions must be strictly followed.

Reinforced

Non-reinforced

3.3 Curbs and Sleepers

At curbed openings, a minimum of one ply of felt shall be carried to inside edge of curb.

Curbed openings (HVAC, skylights, etc.) must be a minimum height of 200 mm (8") and have at least one ply of membrane flashing (stripping) carried to the inside edge of the curb, or up under the built-in counter-flashing of pre-manufactured metal curbs (i.e. roof scuttles or HVAC) (see Detail D1.7.22 Curbs & Sleepers (Basic Curb)).

3.4 Parapets

Parapet walls may be less than 200 mm (8") in height, but not less than 87.7 mm (3½") in height.

All cant edge and parapet wall details must have membrane flashing (stripping) that overlaps the exterior finish (i.e. wall cladding) by a minimum of 50 mm (2"). On high parapet walls, that are completely flashed with metal, where membrane flashing (stripping) is terminated part way up the wall the remainder of the parapet must be covered with a flashing underlay of a minimum 40 mils or 1 mm (.040") self-adhered modified bitumen membrane. 15-lb felt is not acceptable (see Detail D1.7.1 Assemblies (Insulated Conventional)).

3.5 Wall Intersections

Where a parapet, cant or separation / expansion joint detail intersects with a higher wall; the membrane flashing (stripping) must be sealed by gussets (membrane saddles) that are formed to protect the inside and outside corners (see D1.7.6 Parapets & Copings (Parapet - Wall Transition)).

3.6 Sequencing

New construction projects must follow proper sequencing. Where roof flashings overlap work by others (i.e. siding, stucco, etc.), this work must be complete prior to the installation of metal flashing or wood blocking must be installed to facilitate the future installation of the exterior wall finish under the cap flashing. When lapping under work by others (siding, stucco, etc.), the membrane and metal roof flashings must be installed prior to any wall coverings. Any variance to proper detail sequencing must be approved by the design authority in writing.

A reverse lap application method for base sheet and base sheet flashing (stripping), at roof up stand transitions, is permitted when self-adhered base sheet flashing is used as flame protection for wood surfaces. Use of the reverse lap method must be an acceptable application method to the membrane manufacturer.

3.7 Cant Strips

All walls requiring flashing, either bituminous or metal, shall have cant strips installed prior to the commencement of the application of the bituminous roofing membrane. At walls, minimum cant height shall be nominal 75 mm (3"). At roof eaves, minimum cant height shall be nominal 100 mm (4").

(See also 12.3.4 Parapets above)

Wood: Cant strips are only required as recommended by the membrane manufacturer. The use of hemlock lumber for construction of cant strips and related blocking is not acceptable. Wood blocking, well fastened to deck, must be provided under wood cant strips to compensate for insulation thickness on conventional roofs and for the thickness of the under-membrane insulation on modified protected membrane roofs. Alternatively, cant strips may be installed over insulation and solidly attached to the parapet wall.

Fibre Cants: Only fibre cants manufactured from non-combustible materials i.e.: perlitic or fire-resistant fibreboard are acceptable for use on roof systems with torch applied membranes. When fibreboard cant strip is used, wood blocking of equal thickness to the insulation is not necessary unless detailed by specifying authority, or unless required to maintain the structural integrity of the building detail. The use of hemlock lumber for construction of cant strips and related blocking is not acceptable.

The self-adhered base sheet must extend a minimum of 150 mm (6") onto the roof surface. The heat welded field membrane must be turned up at the vertical surface a minimum of 100 mm (4") or a heat welded base sheet transition gusset extending 100 mm (4") onto the roof and upstand surfaces be installed.

Membrane gussets must be installed to all inside and outside corners.

Modified Bituminous Base Sheet pre-stripping ply required at all perimeters, upstands and penetrations. Cap sheet stripping is required and must extend 150 mm (6") horizontally and 200 mm (8") vertically from the base of all upstands.

3.8 Expansion and Control Joints

Roof Separation Joints (Expansion and Control Joints, etc.) / Equipment Sleepers / Safety Anchor Piers (poured in place pads) that are completely sealed (enveloped) with membrane flashing (stripping) may be less than 200 mm (8") in height but must not be less than 100 mm (4") in height above the finished roof surface.

Proprietary elastomeric expansion joint systems, manufactured with an EPDM-based core and flanges that can be fully bonded to the primary membrane, are acceptable for use in low-sloped membrane roof assemblies when the systems are located a minimum of 200mm (8") above the finished roof surface and are completely sheathed (covered) with sloped metal flashing. Such joints must be

a. accepted for use in the RoofStar Guarantee Program;

b. compatible with the roof membrane and acceptable to the membrane manufacturer;

c. designed and manufactured to accommodate building movements of at least 500% elongation at -40° C (-40° F) across its length and at all vulcanized points;

d. factory-fabricated by means of vulcanization;

e. manufactured as one piece, complete with all joints, details and connections;

f. Bonded with the primary membrane in a manner acceptable to the manufacturers of both the expansion joint and the membrane to which it will be bonded.

Field splicing of proprietary elastomeric expansion joints is permitted only when made with a machine acceptable to the expansion joint manufacturer. All other field splices are not permitted.

3.9 Door Openings

Door sill membrane flashing (stripping) may be less than 200 mm (8") in height but must not be less than 100 mm (4") above the primary roof membrane and must be installed to comply with the following conditions:

A metal water stop flashing, formed with pan folded, welded or soldered corners must be mechanically attached to inside of door sill framing or opening and be sealed with membrane flashing (stripping).
Membrane flashing (stripping) or a metal pan sill flashing must be installed at doorjamb framing or opening to a minimum height of 100 mm (4") above door sill framing or opening, prior to installation of doorjambs and door sills.
Membrane gussets must be installed at sill corners.
A metal pan sill flashing or RoofStar-accepted reinforced liquid flashing systems must be installed wherever clearances preclude the use of membrane flashing (stripping) to seal door sill details.
Slopes must be provided to direct water away from door sill details. (Overhangs are recommended wherever practical).
Overflow drains in that area must be installed a minimum 25 mm (1") lower in height than adjacent door sills.
When design or safety codes require minimal elevation changes between a low door sill and an outdoor walking surface (ref. BC Building Code, latest edition), the walking surface must be pavers placed on proprietary pedestals designed with a least 12.5 mm (1/2″) clearance between the finished roof surface and the paver. Alternatively, pea gravel may be used in place of pedestals, but must be installed above a dimple-style drainage board.

3.10 Built-in Membrane Gutters

When a built in membrane gutter joins an RoofStar guaranteed sloped roof; the gutter will be included by the Guarantee. Built-in membrane gutters that drain a roof not covered by a RoofStar Guarantee are not eligible for a Guarantee.

Membranes installed as a gutter liner must be fully adhered and mechanically fastened at terminations. The accepted flexible membrane roofing system must be installed to RoofStar Guarantee Standards and the manufacturer's printed instructions.

Built in gutter membranes must extend up the roof slope to a point, which is 150 mm (6") vertically above the maximum water level of the gutter or outside parapet height (see Built-in gutters and Detail E1.7.17)

Fasteners shall be installed 4” or more above the maximum water line, and gutters must include a scupper overflow drain.