Roof Composition

Roof Composition

Most Common Components of a Residential Roof System

Decks and sheathing of steep-slope roof systems

A deck is the structural base for the roof system. The most common substrate of a steep-slope roof system is wood decks, such as plywood, planks, and non-veneer decking.

Felt underlayment and its purpose

Felt underlayment appearance is black tar paper roofing contractors install prior to installation of the roof system. There are two basic types used for roof systems underlayment.

Field of a roof system

The field of the roof is a major part of the roof system, This usually is the largest portion of the roof system excluding penetration, curbs, cants, flashing, walls, etc. The field of the roof system is considered to be less detailed than other portions of the roof.

Flashings for residential roofs

Flashings are the most common place for a roof leak. The flashings at the penetrations and perimeters must be inspected every year. When re-roofing your home, the proper installation of flashings and edge flashing details is one of the most important steps to a successful roof system.

What are gutters and downspouts used for?

Rain gutters protect structures from ice and water damage. They help carry water off the roof and away from the building. Downspouts direct water away from your foundation.

Roof structural considerations (rafters and trusses)

The rafters and trusses are the main components that support the structure of a roof system, Different factors work against this structure and cause stress on the rafters and trusses. Roof structural failure often begins with rafter deflection or rafter spread.

Why is ventilation important?

Modern home construction methods result in a better insulated and tighter home, which saves you, the homeowner, money on energy bills, but makes the need for a well-ventilated attic even more important. Attic ventilation is necessary to prevent moisture problems and heat build-up, as well as reduce heating and cooling costs. The benefits of proper ventilation for the homeowner are a cooler attic in the summer, a dryer attic in the winter, and protection of the structural integrity of the home from moisture damage.

Why do I need insulation?

How much money are you spending on your monthly energy bill? If you don’t have adequate insulation you may be spending too much. According to the Department of Energy, 50% to 70% of energy used in the average home is spent on heating and cooling.

Most Common Components of a Commercial Roof System

Cants, parapet walls, and curbs on your commercial roof system

One of the most important and valuable parts of a roof system for exterior water entry is the point at which the horizontals of a roof deck and a vertical surface or penetration intersects. A majority of roof leaks occur at these flashing junctures. Designers should carefully design all flashing details around curbs and cants.

Drainage from commercial roofs

A slope of 1-inch in 4 feet is about the minimum practical slope, and even with this it is probable that for large surfaces there may still be depressions where some water will pond.

What are scuppers, through wall scuppers, and drains used for?

A roofs drainage system includes scuppers, through wall scuppers, drains (leaders), as well as the slope provided by the structural deck, tapered insulation, crickets, and sumps. The primary function of the drainage systems is to prevent the retention of water on the roof by removing water as quickly as possible.

Field of a roof system

The field of the roof is a major part of the roof system. This is usually the largest portion of the roof system excluding penetration, curbs, cants, flashing, walls, etc. The field of the roof system is considered to be less detailed than other portions of the roof.

Flashing details on a commercial roof system

Flashings intercept water flow down parapets, down walls of higher adjacent construction, and down roof penetrations diverting it to the membrane. The membrane then carries it to the roof drains, gutters, and other drainage systems.

Roof Penetrations

When inspecting a leaking roof, you should look for poor flashing details — at penetrations, at roof edges, or where a roof changes planes — where areas are much more likely to be the cause of a leak than the roof field itself.

Structural design and available decks

Successful roof systems, along with other factors, rely on sound roof decks. The following provisions should be included in a building’s structural design and in the design of a roof deck.

Unventilated roofs/vapor barriers

Roof designs that provide no ventilated space between insulation and roofing present a more difficult problem of moisture control. Sloped roofs may allow some vapor loss to outside if the surface is shingled or tiled. In low-sloped or flat roofs, the roof membrane is a vapor barrier, in some cases more impenetrable and more complete than any provided on the warm side of the insulation.

Tapered roof insulation systems

Roofing professionals agree there is a need to drain water off a roof surface soon after a rainstorm. Positive drainage is an important aspect of good roof systems.

Insulating your commercial roof system

If you think energy bills are taking a big chunk of change out of your pocket, you are not alone. Americans spend more than $115 billion annually on fuel and electricity for their homes and businesses. On average, heating and cooling (space conditioning) account for about 45% of the energy homes and businesses use. Though energy uses vary, there are many ways to lower your energy bills.

What are the uses for expansion joints on your roof system?

Expansion joints are structural separation between roofing material, which helps eliminate the free movement between elements without damage to the roofing or waterproofing system.


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