Understanding Roofs

One of life’s basic necessities, along with food and clothing, is a roof overhead. A secure and well-maintained roof means more than just physical comfort. It symbolizes the entire concept of domestic shelter and well being.

Some homeowners pay little attention or no attention to their roof, until it leaks. Even then, repairs often are put off until the problem is too great to be ignored.

Roof leaks are more than annoyances, the roof is an integral part of a home that must be repaired as soon as possible. Leaks can cause internal structural damage to a home, which is more difficult and more costly to repair than the leak.

Periodic maintenance is both simple and relatively inexpensive. All it takes is some basic information and conscientiousness.

Please remember that roofing is dangerous work and is best left to the professionals.

What style of roof do you have?

Roof Style
Basic Roof Facts

Roofs have five basic components:

  1. sheathing: boards or sheet material which are fastened to roof rafters,
  2. roof covering: shingles, tiles or other material which protect the sheathing from the weather,
  3. roof structure: the rafter or trusses constructed to support the sheathing and roof covering,
  4. drainage: shape or slope are features which affect its ability to shed water,
  5. flashing: sheet metal or other material laid into various joints, valleys, or protrusions in the roof to prevent water seepage.

Roofs Many Enemies

  • Sun: The warmth and ultraviolet rays of the sun cause roofing materials to loose or dry out substances designed into them, causing them to deteriorate. Southern exposed roofs tend to wear out faster than those facing the North or East. However North facing roofs tend to have algae growth, most commonly seen with black shadowy lines that mark the roof.
  • Rain: When rainwater finds it way through the roof surface, it can set up a moisture condition that is conducive to mold, mildew and rot.
  • Wind: A strong wind can lift shingles off a building, as well as drive water under the edges of roofing materials.
  • Snow/Ice: Melting snow often refreezes at a roof’s overhang, forming an ice dam and blocking proper drainage. Instead water backs up under the roof materials and seeps into the interior of the building.
  • Moss: Wood and built-up roofs are particularly susceptible to the decaying effects of moss. Its root systems can penetrate a roof surface and cause damage to the fasteners. Moss also impedes water runoff.
  • Improper materials: There are many factors involved is determining the proper materials to use on a roof surface. The roofs slope, pitch or angle has a major factor in determining what type of roofing material may or may not be used.

The Scoop on Leaks

While many roof leaks are easy to repair, their sources often are difficult to find. Water dripping from a ceiling may not be from a leak directly above, but from a leak many feet away that runs down a rafter or across a ceiling before coming in. It also could be caused from condensation or just as easy from a plumbing leak situated in a wall or ceiling, and incorrectly attributed to a roof leak.

The most common causes of roof leak are:

  • Improper flashing, sealing or worn-through flashing around projections through the roof such as plumbing vents, chimneys, skylights, dormers, etc.
  • Missing, broken or pierced shingles.
  • Tears in roof valleys
  • Exposed nails or other fasteners
  • Wind driven rain
  • Ice dams
  • Improperly hung gutters or drip edges
  • Improperly installed roofing materials or a roofing material type which is incorrect for the slope involved
  • Cracking and blistering of roof mastic
  • Ponds of water
  • Cracked or disintegrating chimney caps
AsphaltA residue from evaporated petroleum. It is insoluble in water, but solublein gasoline and melts when heated. Used widely in buildings forwaterproofing and roof coverings.
BitumenA generic term used for either asphalt or coal tar pitch.
Class A/Class C ShingleA rating by the Underwriters Laboratories given to roofing material,indicating its ability to withstand exposure to fire originating outside thehouse or building.
CorniceThe trim at the eave line, usually consisting of a fascia board, a soffit fora closed cornice, and appropriate moldings.
Cricket/SaddleA small false roof that is constructed in order to throe off water frombehind an obstacle such as a chimney.
DelaminationThe separation of the layers of plywood sheathing due to exposure tomoisture.
Drip EdgeA piece of metal place over the roof sheathing at the perimeter to deflectwater away from the sheathing and fascia board.
EaveThe lower part of a roof where it meets or projects over a wall.
FasciaA flat board, band or face located at the outer edge of the cornice.
FlashingSheet metal or other material used in roof construction to prevent waterseepage between joints.
LouverAn opening with a series of horizontal slats that permit ventilation butexclude rain and vision.
MasticA material used as roofing cement.
PaperA building material, usually asphalt impregnated cellulose or felt, used inroof construction to prevent the passage of air and water.
ParapetA low wall at the edge of a platform or flat roof that projects above theroof line.
RafterOne of a series of structural members of a roof designed to support theroof surface and load.
RidgeThe horizontal line at the junction of the top edges of two sloping roofsurfaces.
SheathingThe boards or sheet material that are fastened to the roof rafters tocover the house.
ShinglesRoof covering of asphalt, wood, tile, slate or other material cut to stocklengths, widths, and thicknesses.
SoffitThe underside of an overhanging cornice.
Step FlashingThe interweaving of flashing with the roofing material and the materialsof a vertical wall surface, required whenever a vertical wall meets theroofing surface (such as a dormer, skylight, garage or chimney).
TrussThe engineered components that have supplemented rafters in manynewer homes. They are designed for specific applications and cannot becut or altered in any way.
ValleyThe joint formed by the junction of two sloping sides of a roof.
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