Substrates, areas, and conditions shall be examined with installer present, for compliance with the following requirements and other conditions affecting performance of roofing system:
a. Roof openings and penetrations shall be in place and set and braced, and roof drains shall be securely clamped in place
b. Wood cants, blocking, curbs, and nailers shall be securely anchored to roof deck at penetrations and terminations, and nailers shall match thicknesses of insulation
c. Surface plane flatness and fastening of steel roof deck shall comply with project requirements
d. Concrete curing compounds that will impair adhesion of roofing components to roof deck shall have been removed
Built-Up Roofing Installation Procedure
Built-Up Roofing Preparation
Substrate shall be cleaned of dust, debris, moisture, and other substances detrimental to roofing installation according to roofing system manufacturer’s written instructions. Sharp projections shall be removed.
Materials shall be prevented from entering and clogging roof drains and conductors, and from spilling or migrating onto surfaces of other construction. Roof-drain plugs shall be removed when no work is taking place, or when rain is forecast.
At concrete deck, surface of concrete deck shall be primed with asphalt primer at a rate of 0.3 L/m2 (3/4 gal/100 ft²)and primer shall be allowed to dry.
Insulation Installation
- Installation of roofing system components shall be coordinated to ensure that insulation is not exposed to precipitation, or left exposed at the end of the workday.
- Roofing system manufacturer’s written instructions for installing roof insulation shall be complied with.
- Preformed 45° insulation cant strips shall be at installed and secured junctures of built-up roofing membrane system having vertical surfaces or angle changes greater than 45°.
- Tapered insulation shall be installed under area of roofing to conform to slopes indicated.
- Insulation shall be installed with long joints of insulation in a continuous straight line, with end joints staggered between rows, abutting edges and ends between boards. Gaps exceeding 6 mm shall be filled with insulation.
- One or more layers of insulation shall be installed under area of roofing to achieve required thickness. Where overall insulation thickness is 50 mm or greater, two more layers shall be installed, with joints of each succeeding layer staggered from joints of previous layer a minimum of 150 mm in each direction.
- Surface of insulation shall be trimmed where necessary at roof drains, to ensure that completed surface is flush and does not restrict flow of water.
- Tapered edge strips shall be installed at perimeter edges of roof which do not terminate at vertical surfaces.
- Each layer of insulation shall be installed and secured to deck using mechanical fasteners specifically designed and sized for fastening the specified board-type roof insulation to the deck type.
Roofing Membrane Installation, General
- Built-up roofing membrane system shall be installed according to roofing system manufacturer’s written instructions, and applicable recommendations of NRCA Quality Control Guidelines for the Application of Built-up Roofing.
- Built-up roofing system shall be installed with 4 ply, including the base sheet.
- Installation of built-up roofing membrane shall be started in presence of roofing system manufacturer’s technical personnel.
- here roof slope exceeds 1:12, sheets of built-up roofing membrane shall be installed parallel with slope.
- Installation of roofing system components shall be coordinated to ensure that insulation and roofing membrane sheets are not exposed to precipitation, or left exposed at the end of the workday, or when rain is forecast. The following measures shall be taken:
- a. Tie-offs shall be provided at end of each day’s work to cover exposed roofing membrane sheets and insulation with a course of coated felt set in roofing cement or hot roofing asphalt, with joints and edges sealed
b. Terminations and base flashings shall be completed, and temporary seals provided, to prevent water from entering completed sections of roofing system
c. Temporary seals shall be removed and discarded before beginning work on adjoining roofing - Roofing asphalt shall be heated and applied within ± 14 °C (25 °F) of equiviscous temperature (EVT) unless otherwise required by roofing system manufacturer. Roofing asphalt temperature shall not be raised above EVT range more than one hour before time of application. Roofing asphalt manufacturer’s recommended temperature limits shall not be exceeded during roofing asphalt heating. Maximum kettle temperature of type III asphalt shall be 233 °C (450 °F); minimum temperature at point of application shall be 205 °C (350 °F). Roofing asphalt shall not be heated to within 14 °C (25 °F) of its flash point. Roofing asphalt which has been maintained at a temperature exceeding finished blowing temperature for more than 4 hours shall be discarded.
- Roofing asphalt shall be prevented from penetrating substrate joints, entering building, or damaging roofing system components or adjacent building construction.
- In building roofs where there are no parapets, roofing asphalt shall be prevented from running down or dripping on building walls by installing a pitch dam. Pitch dam shall consist of one strip of 300 mm (12 in) wide roofing felt along the entire length of wall eave nailer. Strip shall be folded in half, one half secured to the nailer, and the other half at 90° up, to keep the asphalt from running or dripping on walls. After all plies and asphalt are applied, standing leg shall be folded back over roofing, and secured with flashing cement.
Roofing Membrane Installation
- One lapped course of base sheet shall be installed, extending sheet over and terminating beyond cants. Base sheet shall be adhered to substrate in a solid mopping of hot roofing asphalt.
- Three-ply sheets shall be installed, starting at low point of roofing system. Ply sheets shall be aligned without stretching. Side laps of ply sheets shall be shingled uniformly to achieve required number of plies throughout thickness of roofing membrane. Shingle in direction to shed water. Ply sheets shall extend over
and terminate beyond cants. - Each ply sheet shall be embedded in a solid mopping of hot roofing asphalt applied at the rate required by roofing system manufacturer, to form a uniform membrane without ply sheets touching.
- Lapped granulated cap sheet shall be installed, starting at low point of roofing system. Laps shall be offset from laps of preceding ply sheets, and cap sheet shall be aligned without stretching. Lap in direction to shed water.
- Cap sheet shall be extended over and terminated beyond cants. Cap sheet shall be embedded in a solid mopping of hot roofing asphalt applied at the rate required by roofing system manufacturer.
- Promptly after installing and testing roofing membrane, base flashing, and stripping, roof surface shall be flood-coated with 3 kg/m2 (60 lb/100 ft2 ) of hot roofing asphalt. While flood coat is hot and fluid, the following average weight of aggregate shall be cast in a uniform course:
a. Aggregate weight: 20 kg/m2 (400 lb/100 ft2 )
b. If aggregate surfacing is delayed, glaze coat of hot roofing asphalt shall be promptly applied at a rate of 0.5 kg/m2 (10 lb/100 ft).
Flashing and Stripping Installation
- Base flashing shall be installed over cant strips and other sloping and vertical surfaces, at roof edges, and at penetrations through roof, and secured to substrates according to roofing system manufacturer’s written instructions and as follows:
- a. Substrates shall be primed with asphalt primer if required by roofing system manufacturer
b. If required by manufacturer, backer sheet shall be installed and adhered to substrate in a solid mopping of hot roofing asphalt
c. Flashing sheet shall be adhered to substrate in a solid mopping of hot roofing asphalt applied at not less than 218 °C (425 °F). Hot roofing asphalt shall be applied to back of flashing sheet if recommended by roofing system manufacturer.
- Base flashing shall be extended up walls or parapets a minimum of 200 mm above roofing membrane, and 100 mm onto field of roofing membrane.
- Top of base flashing shall be mechanically fastened securely at terminations and perimeter of roofing.
- Stripping shall be installed, according to roofing system manufacturer’s written instructions, where metal flanges and edgings are set on built-up roofing.
- If required, 760 x 760 mm metal flashing shall be set in bed of asphalt roofing cement on completed roofing membrane. Metal flashing shall be covered with stripping which shall extend a minimum of 100 mm beyond edge of metal flashing onto field of roofing membrane. Roofing membrane, metal flashing, and stripping shall be clamped into roof-drain clamping ring.
Flashing and Stripping Installation
Walkway Installation
- Walkway pads shall be installed using units of size indicated or, if not indicated, of manufacturer’s standard size according to walkway pad manufacturer’s written instructions.
- Loose aggregate surfacing shall be removed, and walkway pads shall be set in an additional flood coat of hot roofing asphalt. If concrete pavers are required, walkway roof pavers shall be installed according to manufacturer’s written instructions in locations indicated, to form walkways. 75 mm of space shall be left between adjacent roof pavers.