Roofing: A Comprehensive Introduction

A roof or a building envelope covers on the top part of a building making a shelter which gives protection from the external environment, elements like animals, weather, rain, heat, wind, sunlight, etc. The function of a roof largely are depends on the purpose of the building that it covers. 

Other factors such as, the roofing materials, the local construction methods, the architectural design and practice, local or national legislation-- all contribute to the function and purpose of the roof.. In most places around the world the function of the roof is to protect against rain. However, sometimes the roof has a special function; the roof of a garden conservatory, protects plants from cold, wind and rain but admits light.

The are many elements in a roof design, some of them are:-:the materials, the construction site, and the weather 

The materials of a roof may range from asphalt shingles,banana leaves, tin, wheaten straw, tin, glass, copper, hard plastic, aluminium sheeting, coating, to precast concrete among may other materials. In many parts of the world ceramic tiles have been the predominant roofing material for centuries, while recently asphalt shingles are the most popular here in the USA. The construction of a roof is determined by how it is supported and how the space under it is covered. Also if the roof is flat or pitched. The pitch is the angle at which the roof goes up, it is calculated of by the number of inches it goes up per feet. So for example, if the roof is 1/12, it means it goes up one inch every feet.-- from its lowest to highest point. In the USA the roof architecture, except in very dry regions, have roofs that have a pitch, thus having a slope. This slope or pitch in measured in terms of 1/12, 4/12, etc. . 

The slope helps to make sure there is no ponding of water, and it works as a drainage system. Nowadays, rainpipes may remove the need for pitch in some cases, roofs are also pitched for reasons of aesthetics.The roof type also determines the pitch, for example thatch roof, requires a steep pitch so that it can be be waterproof and durable. The durability of a roof is also important because the roof is the least accessible part of a building for purposes of repair and installation. On the other hand the weather also plays an important role -- pantiles roof, which become unstable on a steeply pitched roof but provide excellent weather protection at low angles. In places where there is less rain, a flat roof with a slope of 1/12 would provide enough to protect against the occasional rain. Obviously, from previous example we can also see the budget or cost of the roof is one of the most important aspects of a roof construction.The shape of a roof differs greatly from one place of the world to the next. 

Even in the US, there many differences from one region to the next, such as California and Texas. So, local traditions also plays a role in the type of roof that would be installed.Generally, the shapes of roofs are flat, skillion, gabled, hipped, arched and domed. There are many variants and styles in these types. 

Solar roofs

A Newer trend which is slowly growing,, which is most welcomed, are the solar shingles which generate energy from the sun as well as function as cover. There are also solar systems available now, some only generate hot water or hot air while others can power the entire house.Solar systems can be integrated with many other types of roofs. They can be installed as shingles, on tile roofs, on flat roofs, and other systems using different methods like heat welding, fastening, etc.

Drainage

One of the main functions of any (most) roofs is to keep out water of the building structure. As the roof repels or drains water, it should be directed in some suitable way, so that it does not cause damage inside the building structure at the roof and at the foundation. Some of Flat roofs have a very slight slope. In a Middle Eastern countries, the roof is used for recreation and pay. The roof has about 4 feet walls, so people can stand by the roof as people often do in the U.S. by a balcony.These flat roofs have drainage holes to keep water from pooling and seeping through into the building..Commercial properties which often have flat roofs which are very large. it is essential that the membrane be of a impermeable material. In general, the pitch of the roof is proportional to the amount of rain expected every year. Houses in environments of low precipitation usually have roofs of low pitch while those in places of a lot of rainfall and snow, have steep roofs.. In parts of such as Buffalo, USA or Montreal, Canada, there is a required minimum slope of 6 inches in 12 inches, a pitch of 30 degrees.The water removed by the roof during a rainstorm can be damaging to the building. 

If the water runs down the walls, it may seep into the concrete or even through the panels. The foundation also can get seepage into the interior. Its important get water away from the building. Buildings should have a system in place to protect the walls of a building. Overhanging eaves are commonly employed for this purpose. Modern roofs and many old ones have systems of valleys, gutters, waterspouts, water heads and drainpipes to remove the water from the area of the building. It is an interesting side note, In many parts of the world, roof water is collected and stored for domestic use.Areas with heavy snow benefit from a metal roof because their smooth surfaces shed the weight of snow more easily. Metal roofs also resist the force of wind better than a wood or asphalt shingles or even concrete tile roof.

Insulation

Since purpose of a roof is to protect both the possessions and people from the effects of weather outside. Insulation of a roof always an important consideration of the roofs structure.Concrete tiles have been used also a way of creating insulation. The roofs installation is done by leaving a space between the tiles and the roof surface, this reduces heating caused by the sun.There are many different forms of insulation. Some of them are felt or plastic sheeting installed under a asphalt shingle, tile or metal roof, a reflective surface coating, or a synthetic foam batting laid above the ceiling and recycled paper products and other such materials that can be inserted or sprayed into roof cavities like attic. Cool roofs are becoming popular, and in some cases are mandated by local codes. Cool roofs are defined as roofs with both high reflectivity and high thermal emittance; in other words, they provide a good insulation.Poorly insulated and ventilated roofing can create ice dams around the overhanging eaves in cold weather, causing water from melted snow on upper parts of the roof to penetrate into roofing material and then into building itself. This can cause structure damage from stress, including the destruction of gutter and drainage systems.

Outer layer

Before the 20th century, roofs were made from all sorts of different materials like bamboo stick, sea weed, concrete, mud, etc.Then in the 20th century the manufacturing of composition asphalt shingles was invented. Which can last from a thin 20-year shingle to the thickest which are limited lifetime shingles ("limited" lifetime shingles--shingle roofs can expect to be changed at least once every 20 years regardless of what the warranty suggests), the cost depends on the thickness and durability of the shingle, in general. The shingles are easy to replace compared to many other roofing systems.. Another option is to install another layer directly over the worn layer. Having multiple layers of old shingles under a new layer causes roofing nails to be located further from the sheathing, weakening their hold. Most local codes do not allow more then 3 layers. A very critical problem with this method is that the weight of the extra material could exceed the dead load capacity of the roof structure and cause collapse. So roofers have to be very careful not add another layer of shingles without a tear off. Sometimes people like this option since its cheaper. However, its not an ideal situation for the long term.Slate is considered by some the best type of roofing material, the Swiss Alps roofs are made from huge slabs of stone, several inches thick. A slate roof may last 75 to 150 years, and even longer. Slate roofs are very expensive to install – in the USA, for example, a slate roof may have the same value as the rest of the house. Asbestos, usually in bonded corrugated panels, has been used widely in the 20th century as an inexpensive, non-flammable roofing material with excellent insulating properties. Now they are not used as much because of legal issues.Green roofs or garden roofs have good insulating properties and are increasingly encouraged as a way of "greening" the Earth. In areas where clay is plentiful, roofs of baked tiles have been the major form of roofing. The casting and firing of roof tiles is an industry that is often associated with brickworks. While the shape and color of tiles was once regionally distinctive, now tiles of many shapes and colors are produced commercially. Clay is naturally a good insulator.

 Sheet metal in the form of copper and lead has also been used for many hundreds of years. Both are expensive but durable, many copper roofs have been made that are very famous, and lead is used as flashing in valleys and around chimneys on domestic roofs, particularly those of slate. Copper was used for the same purpose.In the 19th century, iron, electroplated with zinc to improve its resistance to rust, became a light-weight, easily transported, waterproofing material. Its low cost and easy application made it the most popular commercial roofing, around the world. Since then, many types of metal roofing have been developed. Steel shingle or standing-seam roofs last about 50 years or more depending on both the method of installation and the moisture barrier (underlayment) used. They cost somewhere in between slate and shingles. In the 20th century a large number of roofing materials were developed, including roofs based on bitumen (already used in previous centuries), on rubber and on a range of synthetics such as thermoplastic and on fibreglass.

There are two parts to a roof, its supporting structure and its outer skin, or uppermost weatherproof layer. In some rare cases of buildings, the outer layer is also a self-supporting structure.

Support

The supporting structure of a roof usually comprises beams that are strong, these beams are made of material such as timber, and since the mid-19th century, cast iron or steel. In countries that use bamboo extensively, the flexibility of the material causes a distinctive curving line to the roof, characteristic of Oriental architecture.

Timber lends itself to a great variety of roof shapes. The timber structure can be very aesthetic as well as fully functional.Stone lintels have been used to support roofs since prehistoric times, the only drawback is they cannot bridge large distances. The stone arches were used by the ancient Romans in different ways. They could be used to span spaces up to 140 feet across in some cases. The stone arch or vault, with or without ribs, dominated the roof structures of major architectural works for about 2,000 years-- and those structures are still standing. Iron beams came into the scene after the Industrial Revolution. Iron beam's were famously used in designing of such buildings as Paxton's Crystal Palace, completed 1851.W

ith continual improvements in steel girders, these became the major structural support for large roofs in commercial use. However, now it is used for residential properties as well. Another common form of girder is the reinforced concrete beam, in which metal rods are encased in concrete, giving it greater strength under tension. Roofing is a very vast subject. 

To learn more call us at DFW Best Roofing at 817 381 6855. We will be happy to do a seminar or workshop on different topics related to roofing.