(a) Decking.

1. (1)

   1. (A) The type of structural deck and the complete roofing system to be used should be determined by the design professional.
   2. (B) Slope for drainage shall be achieved by structural means if possible.
   3. (C) If structural slope is not feasible, a lightweight concrete fill, sloped perlite board, or tapered insulation board shall be specified.

2. (2)

   1. (A) The structural deck must be designed to provide an adequate foundation or base for the roofing system.
   2. (B) In addition to supporting all design loads, it must also be relatively smooth, free of humps, depressions, offsets at joints, allow for expansion and contraction, and be rigid enough to support the equipment and materials needed to apply the roof system without undergoing excessive deflection or deformation, which could impair the life of the roofing system.

3. (3)

   1. (A) Metal decks shall be fabricated from adequate gauge steel, accurately aligned, and securely anchored to the structure below.
   2. (B) Provide side lap connections to prevent displacement between adjacent sheets.
   3. (C) The design professional shall inspect the deck for any possible defects prior to the installation of any insulation and roofing.
4. (4) On poured decks such as concrete, gypsum, and lightweight insulating concrete, adequate drying time for the material shall be allotted prior to application of the roofing membrane.

5. (5) Over low slope wood decks, always specify a nailed down layer of sheathing (five-pound rosin paper) as a separator sheet followed by felt underlayment and a layer or layers of insulation to prevent problems with roofing such as:

   1. (A) Nails backing out;
   2. (B) Expansion; and
   3. (C) Contraction.

(b) Insulation.

1. (1)

   1. (A) Insulation thickness shall be specified by the design professional and be such that when combined with complete roof and ceiling construction, shall have an overall heat transmission coefficient to obtain a satisfactory "R" value meeting applicable energy use codes.
   2. (B) Insulation should have sufficient density and rigidity to span any flutes or irregularities in the decking and support the weight of all anticipated traffic on the roof without crushing or breaking down of the edges.
   3. (C) The design professional or consultants or both shall verify the insulation requirements for each particular building and roofing system.
   4. (D) Provide adequate ventilation in the plenum spaces to prevent moisture and condensation from damaging the interior spaces of the building.

2. (2)

   1. (A) All insulation shall be applied in two (2) layers with all joints broken and staggered.
   2. (B) All insulation boards shall be installed in the same direction throughout unless fields are separated by an expansion joint.
   3. (C) Butt edges of insulation tightly and cut in neatly around all roof penetrations.
3. (3) Insulation shall be secured to deck using approved fasteners conforming to FM Global Class I construction for wind uplift protection unless otherwise approved by the Design Review Section.

(d) Fire, wind, and code requirements.

1. (1) New roof construction on buildings shall meet or exceed all applicable codes.
2. (2) In addition, the roof assembly shall meet or exceed specifications for UL Solutions Class "A" construction and FM Global Class I construction, regarding fire resistivity and wind uplift.
3. (3) When reroofing existing buildings, this may not always be possible, especially when reroofing over existing membranes.
4. (4) Submit plans and specifications to the Design Review Section for approval.

(e) Vapor retarder sheets.

1. (1)

   1. (A) The design professional shall investigate the need for, and specify as required, the proper vapor retarder sheet and its applications.
   2. (B) All buildings with high humidity (such as swimming pools where moisture migration will be a problem) should be specified with vapor retarders unless otherwise approved by the Design Review Section.

2. (2)

   1. (A) The vapor retarder sheet shall be installed over the roof deck prior to the installation of the insulation or roof membrane or both.
   2. (B) Seal all edges, punctures, and around all penetrations through the roof to form an envelope enclosing the insulation.

3. (3)

   1. (A) The vapor retarder application shall meet all fire-retardant requirements which building use requires.
   2. (B) Refer to applicable building codes for requirements.
   3. (C) Determine proper attachment for wind uplift protection from manufacturer's specifications.

(f)

1. (1) Venting base sheets are usually heavy-coated base sheets with an embossed grid designed to channel current moisture out of built-up and modified bitumen roof assemblies and prevent blistering.
2. (2) Venting base sheets are primarily used on reroofing applications or to vent moisture out of poured gypsum or lightweight concrete decks.
3. (3) Application is by spot mopping to existing membranes or mechanical attachment to a nailable deck.
4. (4) In some instances, it is more desirable and economical to use gypsum board or perlite re-cover boards in lieu of a separate venting base sheet.
5. (5) Moisture release vents should always be specified in conjunction with a venting base sheet.
6. (6) See subsection (g) of this section.

(g)

1. (1) Moisture release vents shall be installed on all roof systems when required for certain types of poured decks and reroofing over existing membranes.
2. (2) Vents for bitumen roof systems shall be only factory-made vents with spun aluminum housings designed to vent moisture out but not allow moisture back into the roofing system.
3. (3) Shop-built sheet metal vents are not acceptable for use on buildings.
4. (4) Moisture release vents are primarily designed to vent moisture from a roof system including insulation and to reduce the possibility of blistering.
5. (5) To properly vent, holes should be cut all the way down to the deck, or vapor retarder sheet where applicable, according to the manufacturer's specifications.

(j) Roof surfacing for built-up and modified bitumen roof systems.

1. (1)

   1. (A) For APP (or atactic polypropylene) modified bitumen and built-up roof systems, an Energy Star® approved fibrated aluminum roof coating (asbestos free) (ASTM, D-2824, Type III) applied in two (2) separate coats, at the rate of one to one and one-half gallons per one hundred square feet (1 – 1 1/2 gals/100 ft²), is the preferred roof coating for state-owned buildings.
   2. (B) Aggregate ballast is not recommended for built-up roofing with aluminum coating.
2. (2) For (or styrene-butadiene-styrene) modified bitumen roof systems, use ceramic granules or metal clad “veral”.

3. (3)

   1. (A) For built-up roofs, where aggregate ballast is allowed by code, all aggregate surfacing shall be clean, dry, rounded pea gravel ranging in size from one-quarter inch to three-eighths inch (1/4" – 3/8"), applied as per manufacturer's specifications for the particular installation (four hundred (400) pounds per square minimum is the typical application).
   2. (B) Light color aggregates are preferable to aid in heat reflectivity.
4. (4) Asphalt and emulsion coatings are not recommended.

(k) Roof cants.

1. (1) Roof cants shall be required at all vertical projections including walls, equipment curbs, and the like on bituminous roof systems.
2. (2) Cants shall be securely set in hot steep asphalt or cold applied adhesives.
3. (3) Precautions should be taken to avoid bitumen drippage where it can occur, such as steel decks.
4. (4) Provide a minimum face width of four inches (4") to provide a transition of the roofing felts from the horizontal to the vertical face.

(l) Membrane flashing.

1. (1) All membrane roof flashing shall be compatible with the manufacturer's installed system.

2. (2) Membrane roof flashing:

   1. (A) Shall be provided at all vertical projections, roof perimeters, curbs, parapets, walls, roof penetrations, and elsewhere as required; and
   2. (B) Should be properly designed and carefully detailed to provide a watertight installation.

3. (3)

   1. (A) All membrane flashing at vertical surfaces shall extend a minimum of six inches (6") above the top of the cant strip (ten inches (10") above the roof surface if a four-inch cant is used) and eight inches (8") onto the roof surface from the bottom edge of the cant.
   2. (B) Do not hot mop the base flashing above the top of the cant strip.
   3. (C) Bituminous membrane flashing shall be set in hand rubbed applications of industrial roof cement.
   4. (D) The top edge of the membrane shall be sealed and metal counterflashing provided for protection.
   5. (E) Do not surface mop base flashing of bituminous roof systems with hot asphalt.

(m) Metal counterflashing.

1. (1) Metal counterflashing shall be provided over all membrane flashing where it occurs at vertical projections, parapet walls, equipment curbs, and the like.

2. (2)

   1. (A) A two-piece locking type counterflashing shall be used in all masonry wall construction.
   2. (B) The horizontal flashing part shall be laid in the wall during construction at the proper height.
   3. (C) The vertical face of the counterflashing shall lock in place and be removable to facilitate maintenance and reroofing.

3. (3)

   1. (A) The counterflashing should:

(i) Be approximately four inches (4") in height;

1. (ii) Have a hemmed edge; and

   1. (iii) Turn out at the bottom to form a drip edge.
   2. (B) The counterflashing should never extend below the top edge of the cant.
2. (4) Refer to subsection (n) of this section for the type, gauge, and quality of sheet metal to be specified and used.

3. (5)

   1. (A) Cast-in-place reglets are acceptable.
   2. (B) Specify only nondeteriorating type metal.
   3. (C) Surface-mounted extruded aluminum anchor bars will be acceptable if no other method is feasible.
   4. (D) Anchor bars shall be fabricated of nondeteriorating type metal of sufficient strength and rigidity and have pre-punched, slotted holes for attachment using heavy-duty fasteners.
   5. (E) Note. Plastic anchor pins are not acceptable.

(n) Sheet metal components.

1. (1) All metal components of the roof assembly shall be fabricated of a nondeteriorating metal free of dents, waves, and blemishes.
2. (2) Twenty-four-gauge prefinished sheet metal or mill finish aluminum of thirty-two thousandths inch (.032") thickness (minimum) shall be the standard material used on buildings.
3. (3) Other nondeteriorating metals such as copper and stainless steel are acceptable.

4. (4) Twenty-four-gauge prefinished sheet metal or forty thousandths inch (.040") thickness aluminum is recommended for:

   1. (A) Scuppers;
   2. (B) Guttering;
   3. (C) Down spouts; and
   4. (D) Splash pans.

(o) Expansion joints.

1. (1) Provide expansion joints in the roofing system:

   1. (A) Wherever structural expansion joints occur;
   2. (B) Wherever structural framing or roof decks change direction or materials; and
   3. (C) Where roof areas dictate the need for an expansion joint.
2. (2) Provide additional expansion joints within the roofing system itself wherever the roof perimeter is interrupted by either a projection into or out of the major field of roofing to form an isolated segment of roofing at the same elevation and as may be required by the dimensional stability of the several components used.

3. (3)

   1. (A) Curb-type expansion joints, in lieu of low-profile type, are desirable for purposes of maintenance and longevity.
   2. (B) Treated two by twos (2 x 2s) should be used of sufficient height to install cant strips and membrane flashing of sufficient height for a watertight installation.

4. (4)

   1. (A) Consider using, warranty permitting, metal expansion joint covers of forty thousandths inch (.040") mill finish aluminum in lieu of neoprene expansion joints for all roof and roof-to-wall expansion joint conditions on state-owned buildings.
   2. (B) Hex-head fasteners shall only be used.
   3. (C) Nails are prohibited.

(q) Roof drainage.

1. (1)

   1. (A) All roof drains are to be located at the low points of the roof deck.
   2. (B) Areas drained should be limited so that no drain exceeds four inches (4") in diameter.
   3. (C) Locate drains so that all roof surfaces may be readily drained (each side of expansion joints).
   4. (D) The roof drain itself should be set a minimum of three-quarters inch (3/4") below the roof surface.
   5. (E) Taper insulation in a three-foot diameter around drains.

2. (2)

   1. (A) Coordinate roof drain placement with drainage slopes to stay within acceptable limits according to manufacturer's recommendations.
   2. (B) Install roof crickets between drains where required to properly drain roof areas.
3. (3) Roof drains shall be interior where possible to allow for future expansion of the building.
4. (4) Every roof shall have an appropriate overflow scupper or emergency roof drain to prevent flooding or roof failure should the roof drains become stopped up.

(r) Roof protection walk pads.

1. (1)

   1. (A) In most cases, roof pads or walk boards are not recommended on roofs except in extreme high-traffic conditions.
   2. (B) Roof top protection walk pads are only recommended on roofs where mechanical equipment, flagpoles, penthouses, and laboratory experiments are located which require periodic maintenance and protection from daily foot traffic.
2. (2) Walk pads should be neatly laid out and designed in such a manner as to not impede roof drainage.

3. (3)

   1. (A) Twelve inches by twenty-four inches (12" x 24") is the recommended size of the individual pieces of roof protection walk pads.
   2. (B) Walk pads shall comply with and be installed per roof membrane manufacturer’s warranty requirements.
4. (4) Walk pads should be installed prior to aggregate surfacing or, if smooth surface roof membranes, before the application of the coating.
5. (5) In many instances, simply adding an extra layer of membrane for walk paths and roof protection is preferred.