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Roofing Basics



  • Tile: A roof tile may be curved or flat piece of baked (at times glazed) clay or a synthetic material. It is the basic block used in covering roofs, walls, and floors.
  • Underlayment: It may be any sheet material which is installed in between the roof system and the roof deck. Besides helping in the separation of the two, underlayment also gives secondary protection against potential weather damage.
  • Hip: A sloping ridge that forms the junction between two slopes on a part of the roof that comes out at a separate angle from the main section of the roof.
  • Ridge: A horizontal line formed by two surfaces at the top of a roof where two slopes meet. Basically, it's the peak of a sloped roof.
  • Rake: The inclined edge of the roof which is adjacent to the first rafter of the wall..
  • Vent: An opening in the building designed mainly for the passage of air, water vapor, heat or other gases.
  • Fascia: A face, band, or a flat board which is located at the outer edge of the cornice.
  • Valley: The angle generated by the intersection of the two sliding roof surfaces.
  • Gable: A triangular area that lies directly beneath the sloping roof.
  • Flashing: Metal pieces used as roof joints to protect against water leakage.


  All steep-slope roof systems (roofs with slopes of 25 percent or more) have five basic components:
  • Roof covering: shingles, tile, slate or metal and underlayment that protect the sheathing from weather.
  • Sheathing: boards or sheet material that are fastened to roof rafters to cover a house or building.
  • Roof structure: rafters and trusses constructed to support the sheathing.
  • Flashing: sheet metal or other material installed into a roof system's various joints and valleys to prevent water seepage.
  • Drainage: a roof system's design features, such as shape, slope and layout that affect its ability to shed water.
There are a number of things to consider when selecting a new roof system. Of course, cost and durability head the list, but aesthetics and architectural style are important, too. The right roof system for your home or building is one that balances these six considerations.
  • Asphalt shingles possess an overwhelming share of the U.S. steep-slope roofing market and can be reinforced with organic or fiberglass materials.


   
  • Wood shingles and shakes are made from cedar, redwood, southern pine and other woods; their natural look is popular in California. Some local building codes limit the use of wood shingles and shakes because of concerns about fire resistance.
   
  • Tile—clay or concrete—is a durable roofing material. Tile is heavy. If you are replacing another type of roof system with tile, you will need to verify that the structure can support the load.
   
  • Slate - Considered virtually indestructible, it is, however, more expensive than other roofing materials. In addition, its application requires special skill and experience.
 

   
  • Metal, primarily thought of as a low-slope roofing material, has been found to be a roofing alternative for home and building owners with steep-slope roofs. There are two types of metal roofing products: panels and shingles.


   
  • Synthetic roofing products simulate various traditional roof coverings, such as slate and wood shingles and shakes. However, they do not necessarily have the same properties.
                              
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  • Sun: Heat and ultraviolet rays cause roofing materials to deteriorate over Deterioration can occur faster on the sides facing west or south.
  • Rain: When water gets underneath shingles, shakes or other roofing materials, it can work its way to the roof deck and cause the roof structure to Extra moisture encourages mildew and rot elsewhere in a house, including walls, ceilings, insulation and electrical systems.
  • Wind: High winds can lift shingles' edges (or other roofing materials) and force water and debris underneath them. Extremely high winds can cause extensive
  • Condensation: Condensation can result from the buildup of relatively warm, moisture-laden Moisture in a poorly ventilated attic promotes decay of wood sheathing and rafters, possibly destroying a roof structure. Sufficient attic ventilation can be achieved by installing larger or additional vents and will help alleviate problems because the attic air temperature will be closer to the outside air temperature.
  • Moss and algae: Moss can grow on moist wood shingles and shakes. Once it grows, moss holds even more moisture to a roof system's surface, causing rot. In addition, moss roots also can work their way into a wood deck and structure. Algae also grows in damp, shaded areas on wood or asphalt shingle roof systems. Besides creating a black-green stain, algae can retain moisture, causing rot and deterioration. Trees and bushes should be trimmed away from homes and buildings to eliminate damp, shaded areas, and gutters should be kept clean to ensure good drainage.
  • Trees and leaves: Tree branches touching a roof will scratch and gouge roofing materials when the branches are blown by the Falling branches from overhanging trees can damage, or even puncture, shingles and other roofing materials. Leaves on a roof system's surface retain moisture and cause rot, and leaves in the gutters block drainage.
  • Missing or torn shingles: The key to a roof system's effectiveness is complete protection. When shingles are missing or torn off, a roof structure and home or building interior are vulnerable to water damage and The problem is likely to spread-nearby shingles also are ripped easily or blown away. Missing or torn shingles should be replaced as soon as possible.
  • Shingle deterioration: When shingles are old and worn out, they curl, split and lose their waterproofing effectiveness. Weakened shingles easily are blown off, torn or lifted by wind gusts. The end result is structural rot and interior damage. A deteriorated roof system only gets worse with time-it should be replaced as soon as
  • Flashing deterioration: Many apparent roof leaks really are flashing leaks. Without good, tight flashings around chimneys, vents, skylights and wall/roof junctions, water can enter a home or building and cause damage to walls, ceilings, insulation and electrical systems. Flashings should be checked as part of a biannual roof inspection and gutter cleaning.

Wind Damage

Cupping and Curling Wood Shakes

Incorrect Shingle Exposure

Incorrect Nailing

Incorrect Nail Size

Missing Felt at Roof Eave

Incorrect Pipe Flashing Details

Tile Slippage

Blistering and/or Peeling of Interior and/or Exterior Paint

Possible cause: Excessive temperature or high humidity due to poor attic ventilation.
One of the most critical factors in roof system durability is proper ventilation. Without it, heat and moisture build up in an attic area and combine to cause rafters and sheathing to rot, shingles to buckle, and insulation to lose its effectiveness.

Therefore, it is important never to block off sources of roof ventilation, such as louvers, ridge vents or soffit vents, even in winter. Proper attic ventilation will help prevent structural damage caused by moisture, increase roofing material life, reduce energy consumption and enhance the comfort level of the rooms below the attic.

In addition to the free flow of air, insulation plays a key role in proper attic ventilation. An ideal attic has: A gap-free layer of insulation on the attic floor to protect the house below from heat gain or loss.

A vapor retarder under the insulation and next to the ceiling to stop moisture from rising into the attic. Enough open, vented spaces to allow air to pass in and out freely.

A minimum of 1 inch between the insulation and roof sheathing.

The requirements for proper attic ventilation may vary greatly, depending on the part of the United States in which a home or building is located, as well as the structure's conditions, such as exposure to the sun, shade and atmospheric humidity. Nevertheless, the general ventilation formula is based on the length and width of the attic. NRCA recommends a minimum 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.