Building Materials PDF

What is timber Wood that has been cut down and partially processed to be used for building (for example by cutting it to a certain size) is called timber. Most timber that is employed today is ‘engineered timber’. This means that it is processed to make it stronger so that it can be used in taller b...

What is timber Wood that has been cut down and partially processed to be used for building (for example by cutting it to a certain size) is called timber. Most timber that is employed today is ‘engineered timber’. This means that it is processed to make it stronger so that it can be used in taller buildings. Types of timber The most common type of engineered timber is glued laminated timber, or ‘glulam’. This is made by cutting the wood into layers1. These layers are then glued2 on top of each other. Glued laminated timber is very strong and rigid and can be used to create longer and more resistant beams3 and pillars4 than normal wood. In the past Historically, houses in Britain and many European countries were built using a structural timber frame composed of vertical pillars and horizontal cross beams. The gaps between these were filled with bricks or with ‘daub’, a mix of soil, clay5, and straw6. The frame itself remained visible to the outside, giving these buildings their distinctive appearance. Nowadays Nowadays, timber is used for modern buildings, following a similar principle: the structure is built out of timber, while other materials are used for the non-structural parts. Advantages Light Timber is very light compared to other construction materials. This makes it easy to cut, process, transport, and build with. Strong Timber is flexible horizontally (with the grain), but can endure high vertical forces (against the grain). In fact, in proportion to weight, it is stronger than steel. Environmentally friendly See ECO TOPIC on the next page. Disadvantages Vulnerable to rot7 and pests Timber is vulnerable to pests, rot, mould8 and fungi. Vulnerable to atmospheric agents High temperatures, strong sun, and heavy rain can all damage wood and cause it to warp9 or swell10, reducing its strength Stone What is stone Stone has been used for thousands of years as a building material. It is generally a very durable, strong, and beautiful material. For these reasons, it was in the past often used for monumental, institutional, or military buildings – for example the Pyramids in Egypt, the Colosseum in Rome, even castles in medieval Europe. Types of stone There are many types of stone with di erent advantages and drawbacks, such as limestone, granite, basalt, marble, and travertine. Travertine specifically is a form of limestone that is often used in Italy as a building material. Together with marble, it is one of the most prestigious and expensive types of stone used in construction. In the past Historically, the stones used usually came from quarries1 located near where the building was going to be built. This gives many stone buildings their distinctive colour, depending on what stone was used locally. Nowadays Nowadays stone is mostly used as cladding2material or for flooring3 and decorations, while the structure is made of brick or concrete. Some architects, however, are starting to use stone as a structural material again as a more environmentally friendly alternative to concrete A common way to build structures out of stone nowadays is through slipform masonry4, which consists of placing stone inside a temporary framework5 (a slipform) that is as tall as the finished wall should be. Then, concrete is poured6 in behind the stone and rebar7 is added to make the structure stronger. This method combines many of the advantages of both stone and reinforced concrete. Advantages Low-carbon Stone is a natural material and does not require processing, so its use does not require many carbon emissions. Good insulator It naturally insulates buildings well from noise and high and low temperatures. Disadvantages Not renewable Stone is taken from quarries, which have a finite amount of stone and have a big impact on the local environment. Heavy Because stone is very heavy, it is di cult and expensive to transport. Expensive It is often a material that requires a lot of skilled labour to machine and to assemble Alternative natural materials Clay Clay is a natural material found in rocks or in soil. It is the basis for commonly used materials such as bricks and tiles, which are created by shaping1 and treating the clay and then ‘firing2’ it at a high temperature. However, it can also be used in its ‘raw’ form. In fact, historically, clay, together with earth, was used to make walls. Nowadays, it is sometimes used as an environmentally friendly plaster for walls. Cork Cork is a natural, plant-based material that has been used in construction since Roman times. Although it can’t withstand3 large loads, it’s a light and somewhat elastic material. It also tends to feel warm to the touch; for these reasons, it is sometimes used today as a flooring material. Fabric Fabric is a type of textile, usually formed by weaving together strands of a material, either natural (such as cotton or wool) or artificial (e.g. nylon). It has no structural strength on its own, but can become relatively strong if it is under tension. For this reason, fabric can be used in tensile membrane structures, in which a single element, usually made of fabric that is under tension, serves as the roof for a large space. This type of structure is common for sports facilities and exhibition venues4. The use of fabric as a building material is not to be confused with the term ‘building fabric’, which refers to the structure of a building, of any material, in general. There are also other natural materials such as bamboo, earth and straws, which are used less in modern MAN-MADE MATERIALS Brick What is brick Brick is one of the oldest and most common man-made materials used in building. Bricks are rectangular and relatively small ‘blocks’ that are generally made of dried clay and sand. These materials are pressed into steel moulds1 that have the desired shape and are then ‘burned’ or ‘fired’ in a kiln (a kind of large oven) at around 900-1000°C. This process gives them their structural strength and their appearance. Types of bricks The colour of bricks can vary considerably, depending mostly on the chemical content of the clay which varies from place to place. As a result, bricks made in di erent places from local clay have di erent colours, red in the north of England, yellow in London, grey in Cambridgeshire. Bricks of a type that is common in one particular place are known as ‘stock bricks’ – for example ‘London stock brick’ in London. Advantages Structurally strong Brick is structurally a strong material and has an excellent resistance to compressive forces. Durable and low-maintenance Buildings made of brick can last for a long time with minimal maintenance. Fire-resistant Brick is heat-resistant and does not burn. Disadvantages Time consuming and expensive construction Building brick structures takes a long time and requires specialised labour. Needs firm foundations Brick structures must have solid foundations, because if the building shifts, the bricks may spall and crack. In areas that are subject to earthquakes, this can be extremely expensive. Can be unsuitable for very cold or rainy areas Frost and excessive rain can attack and damage the mortar2 between the bricks, damaging the integrity of the structure Concrete What is concrete Concrete is a building material made of a mixture of fine and coarse1 stone-based aggregates and a binder, such as asphalt or cement. To produce structural elements like walls, liquid concrete is poured into forms, often made of wood. This gives it the desired shape. Once it has hardened su ciently, the forms are removed and discarded or reused. The concrete is then left to cure for several weeks, during which it hardens and gains its characteristic strength through a series of chemical processes that happen within the material. Concrete has a very high compressive strength, but its tensile strength is much lower. To remedy this, it can be strengthened with steel bars that are inserted, like a grid, throughout the concrete structure, creating 'reinforced concrete'. The resulting material is extremely resistant to forces in all directions. Types of concrete The most common type of concrete used today is Portland cement concrete, which uses Portland cement (a very common, grey type of cement) as a binder, sand and gravel as aggregates, n the past Concrete has a long history: the Romans, for example, used a primitive type of concrete to build large structures. However, the use of modern concrete only dates back to the mid-19th century and became widespread around the beginning of the 20th century. Nowadays Concrete, often in the form of ‘reinforced concrete’, is generally used in structural applications, especially in large or tall buildings. We can distinguish between two ways to use concrete in a structure. The first is through precast2 concrete. This is concrete, often in the form of panels, that has been produced and cured in a factory. The panels are then brought to the construction site and assembled. This is a cheaper and more reliable3 method of making concrete structures. The second way is by pouring the concrete directly on site, which gives greater flexibility but is more expensive Steel What is steel Steel is a metal, specifically an alloy of iron, that is often used in construction because of its high tensile strength. Steelmaking is a complex process that involves heating pig iron1 (a type of processed iron ore2) to a very high temperature until it melts. Oxygen is then blown3 onto the liquid iron at a high pressure. This process removes iron’s natural impurities and creates steel, a much stronger material. History During the 19th and 20th centuries, steel became a very popular construction material. Its high strength and durability made it suitable to be used for the pillars and beams for the creation of the structure of large buildings, such as factories and for tall buildings. In fact, some of the most iconic skyscrapers in the world (such as the Empire State Building) have a structure made of steel. Nowadays Steel is still often used as a structural material in its own right. The most common building technique for steel-framed buildings today is the steel frame, in which a regular rectangular grid of steel columns and beams forms the ‘skeleton frame’ of a building. Another common use for steel today is for the creation of reinforced concrete, a material which combines the advantages of both materials (see page 32). Alloy steels It is possible to change the properties of steel by adding small quantities of other elements to it such as manganese, nickel, copper, chromium, and Glass What is glass? Glass is a transparent, brittle1 material with low strength that is not used as a structural material. The most important application for glass in buildings is in windows. Nowadays An increasing number of buildings use large surfaces of glass to allow more light inside and better views out for the occupants. In some cases, entire walls can be made of glass, while another material (often reinforced concrete) is used for the structure of the building. Energy efficiency An important concern with using large surfaces of glass today is energy e ciency. The sheets of glass used for windows have to be very thin (usually around 4 mm), so they tend to transmit heat quite well. This means that in cold climates, the heat inside the building escapes2 very easily, requiring more heating to keep the same temperature indoors. The solution is double glazing: two panes of glass with a small gap between them. This reduces the heat transmission to the outside, making buildings more energy e cient. In some buildings, triple glazing is used to reduce heat transmission furthe