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Roof

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A roof is the top covering of a building. It is a vital part of the building envelope, which is the outer shell that protects a structure. A roof serves many important roles for the people living inside. Most importantly, it protects against rain, snow, wind, and sunlight. It also helps manage extreme temperatures. Some roofs are even designed to provide extra living space, such as a roof garden. Other specialized roofs, like those on a garden conservatory, allow light to enter while blocking wind and rain.

Tak - Ystad-2022
Tak - Ystad-2022

To function correctly, a roof consists of two primary components. The first is the supporting structure, which carries the weight of the entire assembly. This structure is usually made of strong, rigid beams. These beams often rest on the building's walls. The second component is the outer skin, also known as the weatherproof layer. This layer must be able to shed water to prevent it from standing on the surface. Standing water can increase the live load on the structure, which is a safety concern. It can also cause the roofing materials to deteriorate too quickly.

Roof diagram
Roof diagram

The materials used for the supporting structure have changed significantly over time. In prehistoric eras, people used stone lintels to support roofs. However, stone lintels cannot bridge very large distances. The ancient Romans improved this by using the stone arch. This allowed them to span much larger spaces. For about 2,000 years, stone arches and vaults dominated major architectural works. This changed during the Industrial Revolution. The completion of the Crystal Palace in 1851 showed the power of new metal structures. Today, builders use steel girders or reinforced concrete beams. Reinforced concrete uses metal rods encased in concrete to provide strength under tension.

Linkopings stadsbibliotek roof2
Linkopings stadsbibliotek roof2

Architects must also consider the pitch of a roof. The pitch is the angle at which the roof rises from its lowest to its highest point. The pitch is often determined by the local climate and the materials being used. For example, thatch requires a steep pitch to remain waterproof and durable. On the other hand, ceramic pantiles are more stable on roofs with a lower angle. In regions with very little rain, an almost flat roof might be enough. Modern drainpipes can also allow for flatter roofs by managing water runoff. In the United States, most domestic houses use pitched roofs for both practical and aesthetic reasons.

There is a massive variety of materials available for the outer skin of a roof. In many parts of the world, ceramic tiles have been used for centuries. Slate is considered one of the best materials because it is incredibly durable. A slate roof can last between 75 and 150 years. However, slate can be very expensive, sometimes costing as much as the rest of a house. In the 20th century, asbestos was used because it was inexpensive and non-flammable. However, due to health and legal issues regarding mining and handling, it is no longer used for new roofs.

Tak - Ystad-2022
Tak - Ystad-2022

Modern roofing also includes many synthetic and metal options. Metal roofs made of copper or lead are very durable. The copper roof of the Chartres Cathedral has been in place for hundreds of years. Steel shingle or standing-seam roofs can last 50 years or more. Other options include asphalt shingles, which can last from 20 years to a limited lifetime. Some people even use "green roofs," which are made of cut turf or vegetation. These living layers act as insulation to help moderate building temperatures.

Roof diagram
Roof diagram

Maintaining a roof is a serious task for a professional roofer. This is because roofs are often the hardest part of a building to reach for repairs. If a roof fails, the damage to the building can be severe. One common mistake is installing a new layer of shingles directly over an old one. While this is faster, it can be dangerous. It prevents the builder from inspecting the underlying sheathing for water damage. It also adds extra weight, which might exceed the dead load capacity of the structure. This extra weight could even cause the roof to collapse. Because of these risks, some building codes prohibit adding more than two layers of roofing material.

Linkopings stadsbibliotek roof2
Linkopings stadsbibliotek roof2
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File:Tak - Ystad-2022.jpg
Tak - Ystad-2022.jpg
File:Roof diagram.jpg
Roof diagram.jpg
File:Linkopings stadsbibliotek roof2.jpg
Linkopings stadsbibliotek roof2.jpg
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