What is Roof

The roof is the top covering of a building, including all materials and constructions necessary to support it on the walls of the building or uprights, protecting against rain, snow, sunlight, extremes of temperature, and wind. It is constructed to protect the building from weather such as rain, wind, heat, and snow. The roof is the uppermost part of the building. 

Note: All physical objects must bear their weight and, therefore, are ‘load-bearing’ structural elements.

The design of a roof depends on the purpose of the building it covers, the available roofing materials, local construction traditions, and broader architectural design principles. It may also be influenced by local or national regulations. In most countries, a roof primarily shields against rain.

What is Roof

A verandah may be covered with material that shields against sunlight while allowing other elements to pass through. The roof of a garden conservatory protects plants from cold, wind, and rain, while still allowing light to enter. Additionally, a roof can provide extra living space, such as a roof garden.

 

Functional requirements of Roofs 

  • Durable against various natural agencies  
  • Adequate thermal insulation  
  • Waterproof  
  • Fire resistant  
  • Sound insulation  
  • Good drainage arrangements

 

Designing elements of the roof

The elements in the design of a roof are: 

  • The material
  • The construction  
  • The durability 

 

THE MATERIAL  

The material used for roofing can vary widely, from natural options like banana leaves, wheat straw, and seagrass to more modern materials like laminated glass, copper, aluminum sheeting, and pre-cast concrete. Ceramic tiles have been a popular choice for roofing in many parts of the world for centuries, along with other materials such as asphalt, coal tar pitch, EPDM rubber, Hypalon, polyurethane foam, PVC, slate, Teflon fabric, TPO, and wood shakes and shingles.

THE CONSTRUCTION  

The construction of a roof is determined by its method of support and how the underneath space is bridged, as well as whether or not the roof is pitched. The pitch refers to the angle at which the roof rises from its lowest point to its highest point. In most US domestic architecture, except in very dry regions, roofs are sloped or pitched. Even though modern construction elements such as drainpipes may remove the need for pitch, roofs are pitched for reasons of tradition and aesthetics. Therefore, the pitch is partly dependent upon stylistic factors and partially on practicalities.

THE DURABILITY  

The durability of a roof is a matter of concern because the roof is often the least accessible part of a building for purposes of repair and renewal, while its damage or destruction can have serious effects.

Forms OF Roofs

The shape of roofs varies greatly from region to region. The main factors that influence the shape of roofs are the climate, the materials available for the roof structure, and the outer covering. The basic shapes of roofs include flat, mono-pitched, gabled, hipped, butterfly, arched, and domed. There are many variations of these types. 

Roofs constructed of flat sections that are sloped are referred to as pitched roofs. Pitched roofs, including gabled, hipped, and skillion roofs, make up the greatest number of domestic roofs. Some roofs follow organic shapes, either by architectural design or because a flexible material such as thatch has been used in the construction. 

 

There are two parts to a roof:  

  • Its supporting structure 
  • And its outer skin, or uppermost weatherproof layer. 

In a minority of buildings, the outer layer also serves as a self-supporting structure. Walls typically support the roof structure, although some building styles, such as geodesic and A-frame, blur the distinction between wall and roof.

Parts of roofs

Supporting structure  

The supporting structure of a roof usually consists of long, strong beams made of materials like timber, cast iron, or steel. In regions where bamboo is commonly used, its flexibility gives roofs a distinct curved shape seen in Oriental architecture.

 

Timber allows for a wide variety of roof shapes and can serve both an aesthetic and practical function when left exposed. As steel girders improved, they became the primary support for large roofs and eventually for ordinary houses as well.

 

Another type of girder is the reinforced concrete beam, which encases metal rods in concrete to provide greater strength under tension.

 

Outer layer 

This section of the roof displays significant variation depending on the availability of materials. In vernacular architecture, roofing materials often consist of vegetation, such as thatch, with the most durable option being sea grass, which can last up to 40 years. In many Asian countries, bamboo is used for both the supporting structure and the outer layer, where split bamboo stems are laid in alternating and overlapping patterns. In areas with an abundance of timber, wooden shingles and boards are used, while in some countries, the bark of certain trees can be peeled off in thick, heavy sheets and used for roofing.

In the 20th century, composition asphalt shingles were developed. They come in varying thicknesses and durability, with some lasting as little as 20 years and others being labeled as limited-lifetime shingles. The cost of the shingles depends on their thickness and durability.

 

When shingles wear out, they are typically removed along with the underlay and roofing nails to make way for a new layer to be installed. An alternative method is to install a new layer directly over the old one, which is faster but doesn’t allow for inspection of the roof sheathing or repair of water damage often associated with worn shingles. Additionally, having multiple layers of old shingles under a new layer can cause roofing nails to be located further from the sheathing, weakening their hold. The main concern with this method is that the additional weight could surpass the roof structure’s capacity and lead to collapse.

Baked tile roofs have been the predominant roofing material in areas with an abundance of clay. The industry of casting and firing roof tiles is one that is commonly associated with bricklaying. While tile colors and shapes were traditionally unique to a given area, a wide variety of colors and shapes are now commercially produced to suit consumer preferences and budgets. 

 

Function of roofs

The functions of a roof assembly are multiple. It could perform any or all of the following duties:

1. To drain water off the roof, or keep it from collecting there. 

  • There is a safety concern because standing water on the roof surface increases the live load on the roof structure. The majority of roofing materials deteriorate more quickly when standing water is present. 
  • Standing water can invalidate the warranty of some roofing manufacturers.
    To shield the interior of the building from the effects of weather conditions like rain, wind, sun, heat, and snow.
  1. To provide thermal insulation. 
  • Nowadays, batts or insulation boards are a common component of commercial and industrial roof assemblies. 
  • Most of the time, the International Residential and International Building Code determines the minimum R-value needed within the roof assembly. 

 

  1. To perform for the expected service life. 
  • Based on anecdotal evidence, the lifespan of every common roofing material has been established. Most roof materials will last long after the manufacturer’s warranty has expired, given adequate ongoing maintenance, and absent storm damage. 
  • Metal and tile roofs may last fifty years or more. Asphalt shingles may last 30-50 years. Coal tar built-up roofs may last forty or more years. Single-ply roofs may last twenty or more years. 5. Provide a desired, unblemished appearance. 
  • Some roofs are selected not only for the above functions but also for aesthetics, similar to wall cladding. 
  • Premium prices are often paid for certain systems because of their attractive appearance and “curb appeal.”

By Admin

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