ROOFING


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ROOFING


GENERAL INFORMATION


GENERAL INFORMATION


POAH's Portfolio includes sloped and flat roofs. Some, but very few, details overlap between these two roof types.  This section relates to sloped roofs.

 

ROOF SYSTEM COMPONENTS


ROOF SYSTEM COMPONENTS


ROOF SYSTEM COMPONENTS (sloped roofs)

All steep-slope roof systems (i.e., roofs with slopes of 25 percent or more) have the following basic components:

  1. Roof structure: rafters and trusses constructed to support the sheathing.
  2. Sheathing: boards or sheet material that are fastened to roof rafters to cover a house or building.
  3. Roof underlayment: typically asphalt felt applied in rolls directly on top of the roof sheathing. The underlayment is a second line of weather resistance and helps shed water. 
  4. Flashing:  a water impervious component used to 1) diverts water away from openings in- or vulnerable areas of- the enclosure, and/or 2) directs water from behind cladding in an assembly to the exterior.  In a roof assembly, flashing is often sheet metal or rubberized membrane material. Flashing occurs in a roof system at valleys, in locations that the roof abuts a wall (step flashing), and at chimneys.
  5. Roof covering: asphalt shingles, tile, slate or metal that protect the underlayment and sheathing from weather.
  6. Drainage: a roof system's design features, such as shape, slope and layout that affect its ability to shed water.
  7. Insulation: Insulation in attics to meet the following minimum R-values, and to be installed evenly while not blocking soffit vents:
    • R-30 in climate zones 1, 2, and 3
    • R-38 in climate zones 4 and 5
    • R-49 in climate zones 6, 7, and 8
  8. Ventilation:  ridge vents, eave vents, and gable-end vents move air through an attic, reducing the amount of heat and moisture that contributes to mold issues. Baffles should to be used along eaves to promote air movement. Roofs for a vented attic or vented roof configuration include provisions for ventilation.  A roof that meets the requirements for an unvented roof does not need ventilation.
  9. Airsealing: Ideally all attic penetrations (light fixtures, plumbing vents, etc) are sealed to isolate attic from space below.
 

REQUIREMENTS


REQUIREMENTS


REQUIREMENTS:

ROOF STRUCTURE:

All new roofs need to be engineered to support a future PV or Solar Thermal system.

ROOF PENETRATIONS:

All new roof design and construction must coordinate with plumbing and mechanical design/trades to locate vents on the North slope.  Roof surfaces that face South or within 90 degrees of South should be maintained clear of obstructions.

REQUIRED DETAILS:

  • Roof cricket: provide a roof cricket for each chimney, skylight curb or other such penetrations or obstruction with a face perpendicular to the roof slope.  The cricket shall extend at least 4” past the sides pf the obstruction.
  • Kick-out flashing: a flashing shall be installed to divert water away from where the eave of a sloped roof intersects a vertical sidewall. A kick-out/diverter flashing should also be installed at the end of eaves where a gutter is installed at the eave and the gutter does not extend past the end of the eave.
  • Ice barrier: a self-adhering polymer-modified bitumen sheet shall be installed at the roof edge and extend from the edge of the roof deck to a point not less than 24 inches to the inside of the exterior wall line of the building
  • Step flashing: flashings shall be installed at wall and roof intersections.  A self-adhering polymer-modified bitumen sheet shall be installed at roof-wall intersections behind step flashing and extending at least 12” up the vertical face of the wall sheathing.
  • Drip edge: the entire roof perimeter shall be provided with a metal drip edge that has a drip leg extending at least ½” from adjacent fascia or rake trim.
  • Zinc Roof Strips: use zinc strips to kill moss, algae, and lichen growth on the roof. These vegetation with shorten the life of the roof covering. Strips are typically installed at the peaks of sloped roofs.

GUTTER INSTALLATION:

  1. Remove existing gutters carefully if they are to be reused.
  2. Remove any/all screw fasteners at the roof edge.
  3. Install a metal drip edge between the roof panel and the fascia using a polyurethane sealant and screw fasteners.  The drip edge or gutter apron will be inserted at least four (4) inches inside the roof and into the gutter at least two (2) inches.  Please specify sealant in bid.  The sealant should be Sikaflex-221 Non-Sag Polyurethane Sealant or equal in performance.
  4. Install 12" flashing termination of ice+water shield on upper edge of drip edge.
  5. Gutters, existing and new will be installed with the appropriate hangers and spacing to effectively secure them to the building.  Hangers should be no greater than 2 feet apart.  Please specify hanger in bid.
  6. Downspouts will be installed effectivelyto collect and transport water to grade and away from building. Connect gutter to underground storm water system. If using splash-blocks, slope them so water drains away from building. The downspouts should be 4 inc Schedule 40 PVC, painted to match the direct adjacent building color.  Exterior Acrylic Paint specified for plastics should be used.  Provide product information with bid.
  7. Do not install gutter/leaf guard unless approved by POAH Communities Director of Maintenance. If approved, gutter guard should be installed without damaging existing roof or gutter.
  8. Provide an allowance for any work that is required to ensure that the gutter operates correctly once the guard is removed.  Include a scope of work with the allowance.  Items that should be reviewed and confirmed include (but are not limited to) verifying that:
    • The metal roof overhang and drip edge forces rain water to enter gutter and not back into building.
    • There are sufficient hangers to support the gutter
    • The gutters are installed with the correct slope to downspouts.
    • The gutter is installed at an effective distance below the roof edge to allow rain water to enter and not back up into building.
 

VENTED / UNVENTED ROOFS:

Where interior finish is installed directly to the underside of roof framing (or to furring or framing installed to the bottom of roof framing) as a vaulted or cathedral ceiling, an unvented roof configuration shall be used.

Unvented Roof Requirements:

  • The roof shall be designed and constructed with an airtight connection from the roof air barrier to the wall air barrier
  • The unvented roof shall meet the provisions of IRC 806.5 regardless of whether the IRC is applicable to the building

Vented Roof Requirements:

  • Ventilation shall be provided at a ratio of 1 square foot of free vent area for each 150 square feet of attic floor—with vents placed proportionately at the eaves (e.g., soffits) and at or near the ridge.
  • Vented roofs shall have continuous vent openings at eaves and at the ridge. 
  • Where permitted by the roof configuration, a ventilation channel at least 2” deep shall be maintained clear from eave to ridge at each roof framing bay.  
    • Where a skylight, dormer or other obstruction precludes a continuous eave-to-ridge ventilation channel, provision shall be made for venting framing cavities above and below the obstruction.
    • In hipped roof or valley configurations where framing bays do not connect to a bay (valley) or ridge (hipped roof), ventilation openings shall be provided to achieve similar ridge and eave ventilation opening area
  • Wind blocking shall be installed at the perimeter of the attic to prevent roof ventilation from moving through or bypassing insulation.  The wind blocking must be a solid material that is sealed to the wall top plate and to roof rafters.  The blocking should extend to within 2” of the roof sheathing and seal to a vent baffle
  • A vent baffle shall be installed to extend along the roof slope to a point 12” above the top of the attic insulation. Vent baffles should be installed with fasteners to attach them to the rafter.

ROOF/ATTIC CONFIGURATION:

The roof/attic configuration may be vented or unvented. 

Vented attic
A vented attic is appropriate for situations where the roof is relatively simple in form and where there are not conditioned spaces or mechanical distribution located in the roof space.  With a vented attic, access to the attic should be restricted.  Consider providing access through an exterior gable entry.

Unvented attic
An unvented roof/attic is appropriate for situations where there is living space or mechanical systems/distribution in the space enclosed by the roof rafters.  There are two general approaches for an unvented roof/attic: 1) closed-cell spray foam applied to the underside of the roof sheathing, or 2) rigid insulation and a nail base for the roof covering installed to the top side of the roof sheathing (often with supplemental fibrous insulation immediately below the roof sheathing).  The later approach will readily accommodate a vented roof covering (by providing a ventilation space between the rigid insulation and the nailbase).  The unvented roof/attic approach can provide better thermal performance and better resistance to ice dams than a conventional vented attic approach.

PRODUCTS:

  • Architectural Shingles are preferred over 3-tab shingles, as they have a longer lifespan. 

WARRANTY:

  • Labor Warranty: a separate 10-year labor warranty should be provided by the roofing installer. Most roofs that fail during the roof product warranty do so because they were installed incorrectly and in conflict with the manufacturer's recommended installation. 
 

VENTILATION & ICE DAMS


VENTILATION & ICE DAMS


VENTILATION & ICE DAMS:

EXISTING ROOFS:

Ventilation is critical to a roof system's durability and longevity. Never block off sources of roof ventilation, such as louvers, ridge vents or soffit vents, even in winter, or allow bath and kitchen exhaust to terminate in an attic. Without proper air movement and ventilation in an attic, heat and moisture build up and can cause rafters and sheathing to rot, and insulation to become less effective.

Ice dams are a symptom of poor thermal and air leakage control for roofs in cold winter climates. For more information on ice dams and how to avoid them, please view Fine Home Building's article referenced below. 

Note: ice dams are essentially impossible in new buildings built to code.  Incidents of ice damming in newer buildings may be reason to seek remedy from the designer, the contractor or both. 

 

TERMS & VOCABULARY


TERMS & VOCABULARY


VARIANCE FORM


VARIANCE FORM


roofing VARIANCE

Please fill out the following form to submit for a variance.

GENERAL INFORMATION
Name *
Name
VARIANCE REQUEST
What roofing requirements are you seeking a variance for? *