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Roofing

DEFINITION
CONSIDERATIONS
COMMERCIAL STATUS
IMPLEMENTATION ISSUES
GUIDELINES

  1. Fiber-Cement Composite Slates and Shakes
  2. Organic Asphalt Shingles
  3. Metal Roofing Products

CSI Numbers

07300 Shingles & Roofing Tile
07410 Preformed Roof Panels
07500 Membrane Roofing
07610 Sheet Metal Roofing
07620 Flashing & Trim
07316 Metal Shingles
07320 Roofing Tiles
07321 Clay Roofing Tiles
07322 Concrete Roofing Tiles


DEFINITION

This section deals with roof covering materials such as shingles, tile, and roof panels.


CONSIDERATIONS:

In selecting material for roof covering one should take into account its weight (heavier material requires larger support members), its durability (e.g. how well can it tolerate high and low temperatures and for how long), its effect on water falling on the roof if the water is being captured (for example, will gravel from shingles build up sediment in a cistern or do roof materials leach into the water?), the heat-holding qualities of the roof material (does it heat up and stay hot into the night?), as well as cost, fire rating, maintainability, and installation characteristics.

Slate, clay, and cementitious roof materials offer excellent durability but are heavy. Fiber-cement composite roof materials are somewhat lighter and use fiber materials resourcefully. Some use waste paper as well as wood fiber. Many have 60 year warranties.

Metal roof materials, steel and aluminum contain high percentages of recycled content, up to 100% in many aluminum products. An additional advantage is that these materials are easily recycled in their post-use as well as lightweight and durable.

Asphalt shingles use recycled, mixed paper in their base and some use reclaimed minerals in the surface aggregate. This type of material does not last as long as the others mentioned above. Recycled plastic roof materials are starting to be introduced as a lightweight option.

Commercial
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Clay/Cemetitious Satisfactory Satisfactory in Limited Conditions Satisfactory in most conditions Satisfactory Satisfactory Satisfactory
30-50 Year Material Satisfactory Satisfactory Satisfactory Satisfactory Satisfactory Satisfactory
Recycled Content Satisfactory Satisfactory Satisfactory Satisfactory Satisfactory Satisfactory
Satisfactory Satisfactory
Satisfactory in most conditions Satisfactory in most conditions
Satisfactory in Limited Conditions Satisfactory in Limited Conditions
Unsatisfactory or Difficult Unsatisfactory or Difficult


COMMERCIAL STATUS

TECHNOLOGY:

Well-developed; more recycled-content roofing materials can be anticipated.

SUPPLIERS:

Adequate; fiber-cement roof materials are not readily available.

Clay roof materials are costly; metal roof materials are competitive with the more common asphalt shingles.


IMPLEMENTATION ISSUES

FINANCING:

Available.

PUBLIC ACCEPTANCE:

Most people prefer shingle, tile, or slate roof materials; metal shingles are available as an option to metal sheet materials.

REGULATORY:

Roofing materials will meet standards established by the appropriate testing groups and must be installed according to the manufacturers instructions.


GUIDELINES

1.0 Fiber-cement composite slates and shakes

Weigh between 325 and 500 pounds per square.

Use standard roof structures.

Long-lasting (up to 60-year warrantees, fireproof).

Typically have Class A fire rating.

2.0 Organic asphalt shingles

Up to 25% recycled content by some companies.

Life of 20-30 years.

Not easily recycled at end of useful life.

Weigh approximately 230 pounds per square.

3.0 Metal roofing products

Can be made to give shingle appearance

Most metal roofing, including standing-seam, contains recycled metal.

Metal roofing used primarily for agricultural buildings is lower in cost, but requires premium metal coatings, factory-finished panels, or watertight construction detailing when used for housing.

3.1 Metal coatings

Zinc (galvanized) coatings oxidize to protect the steel. Protection is lost when the oxidation process uses up the zinc, and the steel underneath can rust. On low-sloped roofs in wet climates, coating loss and rust can show up in five years.

Aluminum coatings are superior to zinc, carrying warranties up to twenty years. They are inert, and do not degrade over time.

Aluminum-zinc alloys, or Galvalume, will outperform aluminized coatings and exceed twenty-year warrantees.

3.2 Painted metal

Only use factory applied paint.

Polyester resin finishes offer least durability. Fading will occur in 5 to 7 years.

Silicone modified polyester finishes are superior (the more silicone, the better the performance). Twenty year warranties are available.

Fluorpolymer resins provide a state of the art finish. Five paint companies produce this paint under the brand names of Duranar, Nubelar, Fluropon, Trinar, and Visulure.

Bare aluminized or Galvalume panel can last 40 years without maintenance and is a better choice than polyester resin finishes.

3.3 Panel thermal movement

Metal panels respond to temperature change by expanding and contracting. This causes the fastener hole size to increase, resulting in leaks.

Dark colors will experience the largest thermal movement.

Panels installed over purlins will not harm the roof system with thermal movement.

If installing over a solid deck, use Z-shaped metal sleepers over the decking. The sleepers will move with the panels and eliminate fatigue where the screws penetrate the panels (the screw hole will become elongated causing leaks) or the screws will lose grip on the decking. If possible, do not use solid decking with metal roof panels.

Solid aluminum panels have a higher coefficient of expansion than steel and will strain fasteners with the increased movement from temperature change.

3.4 Galvanic reactions

Protect metal panels on the anodic end of the galvanic scale from fasteners and flashings on the cathodic end to prevent corrosion.