What Is a Roof?

What Is a Roof?

Roof protect a home or other structure from rain, snow, sunlight, and extremes of temperature. Its construction includes a frame called a truss or rafters.


The next layer is sheathing, which consists of flat wooden boards. It rests on the rafters, or trusses, and supports other parts of the roof.

A roof is a structure that forms the upper covering of a building, sheltering people and things beneath it from rain, snow, extremes of temperature, sunlight, and wind. It must be strong enough to bear the weight of a building and weatherproofed to resist rain infiltration. A roof should also provide thermal insulation, fire resistance, and soundproofing.

A building’s roof may be flat or have a slope. Its shape and layout depend on the use of the building, local traditions of construction, and wider concepts of architectural design and practice.

In vernacular architecture, the roof is often built with vegetation, such as thatched straw or sea grass. Modern roofing materials may include asphalt shingles, corrugated metal, wood shakes or boards, concrete slabs, or ceramic tile.

The structure that holds the roof covering in place is known as the roof frame or the roof skeleton. It consists of a series of beams called rafters or trusses. It gives the roof its shape and supports the sheathing, the next layer of the roof. The rafters are typically made from long 2×10 or 2×12 pieces of lumber. Some older buildings have exposed rafters, while newer homes use trusses, which are prefabricated and stronger than rafters.

These rafters are joined together with joists, or purlins, which sit perpendicular to them. The joists are then connected to the wall plates of the building with cleats. A king post, which is the central post of a truss, is attached to the joists and has struts that extend out from it. The struts are intended to keep the principal rafters from collapsing inward on each other.

A shed roof has one slope in only one direction, while a peaked or pitched roof has more than one. These slopes are generally not very steep, but they may be as steep as 10 degrees. A dormer is a feature that projects out from the roof, usually to house a window. It can increase the usable space in a room and may even add an extra story to the building. 


The shingles that make up your roof protect the structure of your home and its interior from weather-related damage. They’re available in a variety of styles, materials, and colors to match the look you want for your house.

Traditional asphalt shingles continue to be the most popular roofing material in the U.S. Their easy installation and relatively affordable price make them an excellent choice for many homeowners.

Other types of shingles are available, including metal and slate. Some are more durable than others, but they also cost more to install. Some are designed to resist the effects of heat and moisture, which can help reduce heating and cooling bills.

Some shingles are made to look like traditional wood shakes, which are also an option for many homeowners. Some are designed to withstand the impact of hail or high winds, which can be important for homes in regions with frequent storms. Other shingles have built-in insulation, which can be an attractive feature for many homeowners.

Your shingles may be covered by a warranty from the manufacturer. However, the terms of this warranty can be complicated. For example, it usually won’t cover any problems with your attic ventilation system, and it won’t reimburse you if you have to replace shingles because of severe storm damage.

Before the rash appears, you might feel pain, itching, or tingling in the area where the shingles will form. The rash usually forms a band on one side of the body, such as on the torso or face.

When shingles do appear, the blisters will typically scab over within about 10 days. Afterward, you might be left with some nerve pain that lasts for years, a condition known as postherpetic neuralgia. This condition can be especially painful for older adults, who are more likely to develop it and less likely to recover fully from it.

If you get shingles, your doctor can prescribe antiviral medicine to ease the symptoms and prevent complications. See your doctor for treatment as soon as possible after the rash appears. The sooner you start taking the medication, the less serious your symptoms will be.


Insulation is an important part of a roof since it manages the temperature and moisture within your home. It also reduces mold growth and protects against pests. While opting for roof insulation may add to your expenses for now, you will see a significant difference on your energy bill in the long run. It also helps prevent the transfer of heat from one area to another, which in turn reduces your cooling costs.

There are many insulation materials available, including blankets, rolls, and rigid boards. The best type for your needs depends on the climate, how much space you need to insulate, and the budget you have for it.

Blanket insulation comes in rolls and consists of flexible fibers, mostly fiberglass. It can be cut to fit the nooks and crannies of your attic. It is the least expensive option, but it does not stop air leakage as well as some other types of insulation do.

Rigid insulation boards consist of dense sheets of closed-cell foam. The most popular varieties are polystyrene (EPS), extruded polystyrene (XPS), and polyisocyanurate (polyiso). XPS and polyiso are often coated with aluminum foil, which acts as a radiant barrier. These types of insulation offer excellent thermal resistance but are not water-resistant.

Spray foam insulation is very effective and can be applied to the entire attic or targeted areas that are prone to moisture accumulation. It is very quick to install and offers excellent air sealing capabilities. It does not promote the growth of mold or mildew and is highly fire-resistant.

Cellulose mineral fibers are blown into a void between joists and beams. It is a good option for tight spaces and is suitable for both new and existing homes. However, it must be installed correctly to achieve the desired performance.

Prodex is a special type of roof insulation that combines all the benefits of other insulation types into one. It has a reflective surface that prevents radiant heat from escaping the attic, and it has a low emittance. It is also fire-resistant and has a high R-value, making it very durable.


The drainage that occurs under a roof is important for minimizing the risk of roof leaks and keeping water from pooling on the roof, which can damage almost all roofing materials over the long term. It’s also important to prevent groundwater from accumulating around the foundation of a building, as this can lead to flooding and structural damage.

There are a number of components and design elements that contribute to proper roof drainage. Some of these are relatively straightforward and easy to check, while others require specialized tools and knowledge.

Gutters positioned at the edge of the roof carry rainwater to downspouts, which then direct water away from the building. Downspouts are usually made from PVC or a synthetic (polyethylene, polyvinyl chloride) material, although they can be made from other types of plastic such as ABS (acrylonitrile butadiene styrene). Other materials are used for gutter screens and other flashing components that control the direction of dripping rainwater.

Some buildings have internal drains that work like kitchen sinks or bathtubs, directing water to the interior of the building through pipes. These are typically located on flat or low-slope roofs and are designed to prevent the occurrence of “ponding” water, which is a serious problem for these kinds of roofs.

A “ponding” roof is caused when water accumulates under the shingles, and the most common cause is a poor or missing drainage system. It is important that this be corrected as soon as possible in order to protect the underlying structure and avoid potential problems with the flooring, walls, and other building materials.

James Douglass