ANSWER (1)
CLADDING DEFINITION
In general, cladding occurs when one substance is used to cover another substance, for a variety of purposes. It is the application of one material over another to provide a skin or layer intended to control the infiltration infiltration of o f weather elements, or for aesthetic purposes. Cladding does not necessarily have to provide a water-proof condition but is instead a control element. This control element may only serve to safely direct water or wind in order to control run-off and prevent infiltration into the building structure. Cladding applied to windows is often referred to as window capping capp ing and is a very specialized field. In metalworking, cladding is the bonding together of dissimilar metals. It is distinct from welding or gluing as a method to fasten the metals together. Cladding is often achieved by extruding two metals through a die as well as pressing or rolling sheets together under high pressure. The United States Mint uses cladding to manufacture coins from different metals. This allows a cheaper metal to be used as filler. In fiber optics, cladding is one or more layers of material of lower refractive index, in intimate contact with a core material of higher refractive index. The cladding causes light to be confined to the core of the fiber by total internal reflection at the boundary between the two. Light propagation in the cladding is suppressed in typical fiber. Some fiber can support cladding modes in light propagates in the cladding as well as the core. METHOD
OF CONSTRUCTION
In construction, cladding is used to improve building durability and maintain constant temperatures within the structure. Rain screen cladding is also used to improve the weatherresistance of buildings through the use of multiple layers of rain and environmentally resistant materials. Over cladding is another type of building cladding. In this type of cladding, a new "skin" of a cladding material is applied over the top of an existing layer of material. This is done
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to improve the appearance or function of the building. Some of the materials used in construction for cladding are: stone, concrete, co ncrete, metals such as steel and aluminum, glass, plastic and ceramics. The performance and complexity of construction of a particular system can be greatly influenced by certain strategic responses to the envelope design. The relationship between the frame and the cladding, exposed or protected, is important both in terms of performance and expression. In a protected frame, the t he structure is completely enclosed by the cladding. The cladding protects the frame from the weather and extremes of temperature. The connection of the cladding to the frame is easier than in the case of the exposed frame. The expression of the cladding may be completely independent of the frame behind. LASER CLADDING: Laser cladding is a method of depositing material by which a powdered
or wire feedstock material is melted and consolidated by use of a laser in order to coat part of a substrate or fabricate a near-net shape part. It is often used to improve mechanical properties or increase corrosion resistance, repair worn out parts, and fabricate metal matrix composites. Process
The powder used in laser cladding is normally of a metallic nature, and is injected into the system by either coaxial or lateral nozzles. The interaction of the metallic powder stream and the laser causes melting to occur, and is known as the melt pool. This is deposited onto a substrate; moving the substrate allows the melt pool to solidify and thus produces a track of solid metal. This is the most common technique; however some processes involve moving the laser/nozzle assembly over a stationary substrate to produce solidified tracks. The motion of the substrate is guided by a CAD system which interpolates solid objects into a set of tracks, thus producing the desired part at the end of the trajectory. A great deal of research is now being concentrated on developing automatic laser cladding machines. Many of the process parameters must be manually set, such as laser power, laser focal point, substrate velocity, powder injection rate, etc., and thus require the attention of a specialized technician to ensure proper results. However, many groups are focusing their attention on developing sensors to measure the process online. Such sensors monitor the clad's 2
geometry (height and width of deposited track), metallurgical properties (such as the rate of solidification, and hence the final microstructure), and temperature information of both the immediate melt pool and its surrounding areas. With such sensors, control strategies are being designed such that constant observation from a technician is no longer required to produce a final product. Further research has been directed to forward processing where system parameters are developed around specific metallurgical properties for user defined applications (such as microstructure, internal stresses, delusion zone gradients, and clad contact angle). SEQUENCE OF OPERATION 1.
Fitting the wall battening
2. Fitting the cladding 3. Dealing with corners and ends 4. Finishing off
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1. Fitting the Battening
Secure the battening around the entire perimeter of the area being clad including around window and door frames. Pack it out where necessary on uneven walls. Infill either vertically or horizontally with intermediate lengths of battening again packing out where necessary to make a complete level framework not following uneven wall contours. Diagram B . Note the extra battening around the electric socket and switch. Take care not to drill into electric cables hidden in the wall. To get an idea of the likely direction in which the power cables run disconnect the power at the main, remove the switch or socket cover and note from which direction the cables enter the box. Flush electric fittings will need to be moved forwards and secured to the battening around the boxes so that they remain as flush fittings when the cladding is in place. Surface fittings can either be left in place, and cladding fixed up to the sides or they can be moved forwards and fitted to the surface of the cladding. 2. Fitting the Cladding Vertical Cladding
The first length of cladding is fixed at one end of the wall butting up against the return wall, if there is one, and pushed tightly against the ceiling. Any gap at the bottom will be covered by skirting. The grooved edge of the first board should be against the wall. Lightly secure the first length of the cladding using only two or three nails driving them in through the face of the board close to the wall into the vertical perimeter battening. Do not drive the nails fully home yet. Check with a spirit level that the board is perfectly vertical Diagram C. It may be necessary to shape the grooved edge of the board to achieve the level if a return wall is very uneven or out of true. Once vertical drive the nails fully home. Punch the heads below the surface for filling in later and also drive nails through the tongue on the opposite side. The tongue fixing on this and subsequent boards will be concealed by the groove of adjacent boards. Using an off cut of cladding to protect the timber, tap the board snugly against the first from top to bottom. Diagram D. Nail to the battens through the tongue only. Fix all subsequent boards in the same way. Cladding Clips can also be used but refer to Table A for details. Some will need to be cut to fit around the door or window frames or 5
electrical fittings. The last length will probably need to be trimmed to fit in and like the first will need to be face nailed into place. Horizontal Cladding
The general fixing procedure is the same as for vertical cladding. The first length is fixed perfectly horizontally tight up against the ceiling with the grooved edge uppermost. When more than one length of cladding is needed on a long wall, make simple butt joins, fitting an extra piece of battening to the wall behind the join. Diagram E. This use of small pieces of battening avoids wastage of timber and ensures that joins are staggered, i.e. not all in line d own the wall. Diagonal Cladding
This requires rather more careful planning than vertical or horizontal cladding. Diagram F shows some possible layouts with all joints having 45° miters. It is advisable to stick to this
angle for simplicity. Battening can be horizontal or vertical and each board will need to be cut individually to a measured length. 3. Corners and Ends
You will almost certainly need to provide a neat finish to the ends and corners of your cladding. Quadrant or Scotia moldings can be used on internal corners, Diagram G, and right angle beading or small section planed timber fitted to external corners, or around window and door frames. Diagram H. Ceilings Standard : Battening should be used to make a framework for the cladding as with walls, but
attached to the ceiling joists. 4. Finishing Off
Timber cladding must be sealed to prevent it becoming dirty and affected by moisture. Our Wood care varnishes, in either a matt, satin or gloss finish, can be used. At least three coats
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should be applied following the instructions on the container. Alternatively, use Wickes High Performance Wood stain. The number of coats applied controls the final colour of the cladding. (See packs for details or table A). Exterior Cladding Exterior
cladding does not differ much from interior cladding except in the treatment of
the timber which naturally needs protection from the weather and the positioning of the boards when used horizontally. Cladding is fixed with the grooved edge facing downwards. Use one of our Exterior Timber Preservatives or Wickes High Performance Wood stain. This is a micro porous preservative which allows the timber to 'breathe' so that moisture can evaporate without causing the surface finish to lift off or peel in the way that paint or varnish films may. Interior PVC Cladding
Wickes interior PVC cladding is ideal for use in situations where a maintenance-free or easy-clean finish is needed such as in bathrooms. It is fitted in much the same way as timber cladding being pinned to battening. It is normally fitted horizontally with the tongue to the top. There is a selection of 'accessories' available to ensure that the cladding which is hollow can be installed with a neat finish at corners, ends and joins. Diagram I shows these PVCu profiles and indicates their uses. All the profiles, and the cladding, can be cut with a fine toothed saw such as a hacksaw. There are a number of ways in which the cladding can be used. On a ceiling the cladding can be fixed to its battening with straightforward butt joins to the walls at either end or the sides. Alternatively the coving profile can be fitted around the perimeter of the ceiling, on battening, and the cladding cut to slot in the coving. Diagram J. A wall with a return at either end can be clad without any edgings used or again the coving can be fitted at the top and in the wall corners or just up to the ceiling. Around window or door frames the end cover bead can be used. On walls with an external or internal corner with cladding to be continued around the corner, the external/internal corner profile is used to make a neat edge. Where the lengths of cladding needed are longer than 2.5 meters the butts join profile is used.
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Calculating Your Cladding Requirements
To determine how much cladding is required measure the width (or height) and length of the area to be covered. Decide which way the cladding is to run and divide the measurement at 90° to the run direction by 100mm-the effective coverage width of the cladding. This will tell you how many board widths will be required. Then work out how many 2.5m lengths of cladding will be needed to cover the area either in full length pieces or joined pieces.
Effectively
the
technique is the same as for measuring for timber cladding. Fitting Procedure
For battening, read the instructions given for timber battening previously in this leaflet. The cladding is fitted in the same way as timber cladding with concealed nail fixings through the tongues. Where face fixings are necessary use white screw covers to conceal the screw heads. White silicone Frame seal may be used to secure cover beads to wall surfaces. If the width of a piece of cladding has to be reduced this can be done with a sharp trimming knife along a straightedge. Always ensure that the cladding is secured perfectly horizontally or vertically. USAGE
Timber cladding should never be fixed directly to walls or ceilings which are invariably uneven. It should be fitted to a framework of timber battening fixed to a wall using masonry nails or screws and plugs, or to a ceiling using screws into the joists above. Use something like our 22 x 38mm Cladding Battens for this framework. The need for this timber must be taken into account when calculating your material requirements. You will need sufficient to secure around the entire perimeter of the area to be clad and to fit between at intervals, full length horizontally for vertical cladding and vertically for horizontal cladding. To calculate how much cladding is required you must measure the width and length of the area to be covered. For vertical cladding the wall height will determine the board lengths needed - probably 2.4m ones in the majority of homes. The width of the wall must be measured in millimeters and this figure divided by the effective covering width of the boarding to be used, as detailed above. The resulting figure will 8
give you the number of lengths required. For example if a wall 4547mm long is to be covered with Heritage cladding which has an effective coverage of 86mm your sum is 4547 divided by 86, which equals 52.89. 53 boards will therefore be needed. For horizontal cladding measure the wall height in millimeters and again divide by the relevant width coverage of the chosen cladding. Always round figures upwards and it is generally wise to add a couple of boards to the tally in case of cutting errors. ADVANTAGES OF CLADDING
Cladding serves as a control feature, protecting the building from the elements. Types of cladding materials include wood, plastic (or vinyl), imitation stone or brick, and metal. Wood siding can include Eastern white pine, plywood sheets, wood shingles, cedar and redwood. Metal siding can be aluminum and galvanized steel. The advantages are stated below: (1)
LOW MAINTENANCE
The most prominent advantage to cladding a building is the minimal maintenance required as compared to painting. Most external cladding requires nothing more than regular washing to maintain its newness.
Extruded
aluminum cladding, for instance, is used for walls,
facades, canopies, roofs and column covers. It provides durability and long-lasting resilience, protecting the structure from external weather elements, while requiring almost no maintenance. Vinyl siding is a common finish used on building facades in the United States. It is made of polyvinyl chloride (PVC) panels, which are easy to install, cut and replace. PVC cladding requires no maintenance other than a power wash every two years. Stone or brick veneer cladding is an expensive upfront investment, but it is likely to last for decades without any maintenance. (2)
SAFETY AND PROTECTION
The basic purpose of external cladding is protection. It increases the mechanical strength of a structure, improves its resistance to cracking during increased temperature change, reduces water absorption, increases resistance to sunlight, and provides resistance to air and chemical pollution. Cladding also offers protection against the rain, strong winds and molds. 9
(3)
AESTHETIC VALUE
Building cladding transforms the look of an otherwise drab structure, making it aesthetically appealing and increasing its market value. Granite wall cladding, for instance, is available in a variety of textures and colors. It may be polished, finished or left rough, depending on the aesthetic requirements of its builders. A large variety of brick cladding solutions are available, including white stone, vintage, rustic, rosebud and greywood. Each type provides a unique look to a building facade. Stone cladding is available in a wide range of colors, including light golden, cream, beige, charcoal, and yellow. FOR PLASTIC CLADDING
The advantages are: (a) They can be cleaned much more easily. Wiping plastic down is a lot easier than cleaning brick or wood - and this are a big factor in the increasing popularity of plastic cladding. (b) Plastic cladding is very strong and can withstand a lot of stress. It can handle high temperatures and extreme cold as well. It can even take on strong winds. (c) Another major benefit is in the price, Wood and brick cladding is a lot more expensive, and plastic cladding is a great cost-effective alternative. (d) Plastic cladding can give you is that it is much easier to replace than other types of cladding. In the event of fire, for example, it is likely that at least some of your cladding will need to be replaced, no matter how durable it may be. FOR BRICK CLADDING
The advantages are: (a) Available in cast stone facings. (b) WIMLAS third party certification approved. (c) Durability and aesthetic quality with minimal maintenance that only fired clay brick provides.
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(d) Waterproof insulating backer panel provides thermal benefits in both new build and existing structures in refurbishment. (e) Simple to install over timber frame, metal stud or masonr y, by semi-skilled labour. (f) Light in weight from 29 kgm/m2 reduces cost of support structure and foundations as well as eliminating heavy handling equipment. (g) Installation rate is over three times faster than conventional masonry. (h) CFC free height quality extruded polystyrene foam backer panel is available up to 50mm thick giving a system U value of 0.49w/m2. (i) Available for internal work bonded to 12.5mm plasterboard. (j) Simplifies installation of elaborate colour relief brickwork patterns. (k) Can be installed as a final finishes element, minimizing risk of damage by other trades and improving cash flow in pro ject expenditure. (l) Twenty year system guarantee. (m)Twenty year system guarantee. FOR METAL CLADDING
The advantages are: (a) It is Cost saving. (b) It has foreign substitute. (c) It has a Large surface area can be cladded up to 30 Sqm. (d) It has widely differing in physical properties can be bonded. (e) Reactive metals like Aluminum, Titanium, and Zirconium on steels, Steel forgings and .Steel can be bonded. (f) Metallurgically incompatible metals can be bonded. (g) It has Superior bond strength over other bonding methods. (h) Homogeneous cladding layers and Superior structural integrity between dissimilar metals. (i) It has better forming characteristics. (j)
Excellent
electrical characteristics and long term stability.
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DISADVANTAGES OF CLADDING (a) COST
Cladding can be very expensive, depending upon the material. While timber or metal cladding can be relatively inexpensive, concrete cladding can result in a large bill due to the increased amount of labor required. (b) TIME
Depending upon the size of the structure and the material used, the installation of siding can take a long time. This also depends upon the quality of the original structure, which must be sound enough to support the cladding. (c) REPAIR
While cladding is low-maintenance--requiring a simple wash on a regular basis--if it is broken or dented, its aesthetic qualities are reduced and it may be difficult to repair the damaged part. This is especially common with metal cladding, which can easily be dented. Also, if the cladding is not installed properly, the underlying structure can be damaged. (d) Stone cladding requires an additional insulation layer, to prevent heat loss in cooler weather. (e) Stone cladding includes the possibility of trapped moisture within the walls of the building and difficulty in its insulation or replacement.
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(2) SUSPENDED CEILING DEFINITION
This is a dropped ceiling is a secondary ceiling, hung below the main (structural) ceiling. They may also be referred to as a drop ceiling, false ceiling, or suspended ceiling, and are a staple of modern construction and architecture. It is also a ceiling which is not a part of the structural framework of a building and is installed below the level of the underside of the floor above or of the roof. A suspended ceiling consists of tiles that fit into a metal grid installed below the structural ceiling of a room. This type of ceiling is frequently used in commercial buildings, but also works well in residential structures. METHOD
OF CONSTRUCTION
Manufactured suspended-ceiling systems are made from slim metal sections, which provide a fairly lightweight structure for acoustic or translucent panels. They are quick and easy to fit and do not require specialist tools. Manufactured
systems
Manufacturers offer a choice of finishes for the framing as well as textured, translucent and opaque panels. The lightweight alloy framework is made from three basic elements: an angle section, which is fixed to the walls; a main-bearer section, which spans the shortest direction; and a lighter T- section cross bearer, which bridges the space between the main bearers. The loose panels sit on the flanges provided by the bearers. They can be lifted out easily to provide access to ducting or for servicing light fittings concealed behind them. You need at least 200mm (4in) above the framework in order to fit the panels. Normally, 600mm (2ft) square panels are used for suspended-ceiling systems. Before fitting the framework, draw a plan of the ceiling on squared graph paper to ensure that the borders are symmetrical (see far left). Draw a plan of the room with two lines taken from the halfway point 13
on each wall to bisect at the centre. Lay out the grid on before building a suspended ceiling with translucent panels, remove flaking materials and make good any cracks in the plaster ceiling above. Paint the ceiling with white emulsion to improve reflectivity if concealed fluorescent lighting is to be used. Fix fluorescent light fittings to the joists, spacing them evenly across the ceiling: 16 watts per square meter is recommended for a suitable level of light in most rooms. Mark the height of the suspended ceiling on the walls with a continuous leveled line. Hacksaw two lengths of angle section to fit the longest walls. Remove burrs from the ends with a file. Drill screw holes at 600mm (2ft) intervals. Drill and plug the walls, using the angle as a guide, and screw the components in place (1). Next cut lengths of angle to fit the shorter walls. Their ends should fit on the angles already fitted. Screw-fix them in the same way. Mark the positions of the bearers along two adjacent walls, as set out on the graph paper. Cut the main bearers, your plan with a main bearer centered on the short bisecting line (1), and then laid it out again with a line of panels centered on the same line (2). Use the grid that provides the widest border panels. Plot the position of the cross bearers in the same way, using the other line (3,4). Try to get the border panels even on opposite sides of the room (5) to span the room. Sit them on the wall angles (2). Use a ceiling panel to check they are parallel and at right angles to the wall and each other. Cut the border cross bearers to fit between the end main bearers and wall angles. Set them in line with the points marked on the wall. Position the remainder of the cross bearers following the same line. Working from the centre, drop in the full-size panels. Measure and cut the border panels to fit and then drop them into place. Spanning wide rooms, if the size of the room is such that it exceeds the maximum length of the main bearer, join two or more pieces together. A joint bridging piece is provided if the ends of the bearers are not made to lock together. For spans exceeding 3m (10ft), support the main bearers with wire hangers. Fix each wire, spaced not more than 1.5m (5ft) apart, through a hole in the bearer and hang it from a screw eye in a furring strip or joist in the ceiling.
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SEQUENCE OF OPERATION OF SUSPENDED CEILING 1.
Determine the maximum height of the suspended ceiling. Typically about 4 in. from
the existing ceiling joists, this provides enough space to angle the tiles into place. (If installing drop lights, then go 6 in. from the joists.) Mark the wall and then draw a line around three sides of the room using your level. 360 Degree laser level work best, or a 3' - 4' level to draw a line around the entire room. If using a hand level you'll need to use a chalk line once the marks are made so you have a straight line. Laser Line levels will provide a nice bright red line around the room. 2. With the perimeter lines established, nail or screw the perimeter molding ( L shaped bracket in the grid kit) in place, preferably in the wall studs, so that the top edge of the bracket lines up with the perimeter line. Cut the molding to fit with tin snips in corners or along oddly shaped walls. For long walls, butt the ends of two pieces of molding. For outside corners miter each bracket at 45 degrees and butt together. 3. Before installing the main runners, use string to lay out where the main runners are to go, this will be perpendicular to the joists and should be 4ft apart. Measure the length and width of the room, and from the center of the string runners, so the ceiling appears balanced from side to side depending on the size tile you are using. Doing this saves A LOT of time and string is easier to move than the main runners. 4. Once the string grids for the runners are in place and you are happy with the balance, install the main runners¶ perpendicular to the joists and 4ft. apart. Depending on the type of ceiling grid system you use, the main runners will either be in sections of 4ft, 6ft, or 8ft sections that snap together. Support the main runners with 16-gauge wire into eyebolt screws that you screw into the floor joists about every 3rd joist. Use string stretched between perimeter moldings to determine height of runners. Using a smaller level every 4ft. across the runners as you hang with wires will keep your runners level all the wa y across the room. 5. Tie the runners together with the cross tees. Start in the center of the grid to square the grid. Keep in mind the type of system you've chosen, either 2 x 4-ft or 2 x 2-ft panels, and place cross tees in accordingly. It's a good idea that as cross tees are placed to place a few tiles in along 15
the way, but not all tiles should be placed at this time in case you need to move a few of the cross tees. 6. No doubt that you may need to trim a few tiles. If the tile you choose is smooth cut on the finished side, however if the tile you choose is more textured, cut on the back side to trim. Always use a sharp utility knife, less dust and better results than with power tools. USAGE
Ceilings hide the framing of the floor or roof above, plumbing pipes, ductwork, electrical wire, insulation.
Ceilings needn't just look nice; they can also do things: muffle noise, support lights, retard flames.
Suspended ceiling is used in most industrial and commercial buildings such as offices, schools and hospitals.
They are also used to hide piping, wiring and ductwork.
Suspended ceilings can also help with reducing sound and with minimizing thermal loss from your room.
ADVATAGES OF SUSUPENDED CEILING
(a) It can be installed in any room or all the rooms of any building, from your residence to a supermarket. (b) By having a suspended ceiling, you are reducing the virtual area of a given room. That is sure to have some positive effects on the system of air-conditioning, which naturally gets more effective. (c) In a way of maintenance, you can conveniently dismantle a part of the ceiling by removing a couple of tiles, carry the needed repairs and replace the tiles that were removed. (d) It provides protection against fire with the tiles made of special mineral fibers. These tiles are fire-proof and conform to fire codes. In the unfortunate incidence of a fire, the surface will retard fire and thus may save goods and human life. (e) A suspended ceiling can significantly help with room above it for the w ires and/or piping. 16
(f) Suspended ceilings are easily installed in a home of office. In fact, many homeowners with the required knowledge can purchase the materials and perform the installation themselves. However, to maintain the safet y of your home or office, it is wise to consult a licensed contractor for advice before installing suspended ceilings. (g) A suspended ceiling can easily conceal imperfections and flaws on the actual ceiling. Instead of performing costly repairs and painting, you can install a suspended ceiling to cover pipes, ductwork, stains and peeled paint. Beware of this if you plan to purchase a home with suspended ceilings. Make sure you have some panels removed and inspect the space above to make sure there are no structural issues. (h) By installing a suspended ceiling with fiber glass, you can block out all the sounds from outside. This makes a room much cozier. (i) You can install lights, fans and other overhead appliances easily between panels of a suspended ceiling. Some lights the same size of the panels can also be installed at regular intervals in place of panels. (j) Suspended ceilings are available in wood, plastic, fiber and other materials. Some panels also have an added degree of fire protection. (k) It allows better lighting and light reflection. DISADVAVTAGES OF SUSPENDED CEILING
(a) There is going to be reduced headroom in the room considering you are technically hanging a second ceiling under the first so before you get these ceilings installed you may want to think about whether or not it is going to be a pain for being to low o r not. (b) Sometimes walls do not extend past the grid to the actual ceiling. This can present a security risk when used in offices or areas where unauthorized entry may be an issue. (c) As a renovation tool, dropped ceilings are a quick and inexpensive way to repair a ceiling or reduce HVAC costs, however they tend to show their age quickly² they are sometimes discolored by excessive smoking, sag in the center, and are damaged easily. In older buildings that have seen multiple renovations over time (d) In case you are using the vertical space for display or storage of items in a store, you may feel the pinch of lack of storage area along the walls. False ceiling may not suit a display area that uses the ceiling for suspenders to display items. It will be good to make a 17
calculation of the area that would be eaten up by a suspended ceiling before you go for its installation. (e) Suspended ceilings do not last very long. They often tend to sag and show discoloration and stains after a few years of use. Frequent maintenance is required to maximize the lifespan. (f) In the event of an earthquake or a fire, suspended ceilings may be very unstable. There is also the added danger of the installed fixtures falling on people underneath.
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(3) CURTAIN WALLING DEFINITION
This is an outer covering of a building in which the outer walls are non-structural, but merely keep out the weather. As the curtain wall is non-structural it can be made of a lightweight material reducing construction costs. When glass is used as the curtain wall, a great advantage is that natural light can penetrate deeper within the building. The curtain wall façade does not carry any dead load weight from the building other than its own dead load weight. The wall transfers horizontal wind loads that are incident upon it to the main building structure through connections at floors or columns of the building. A curtain wall is designed to resist air and water infiltration, sway induced by wind and seismic forces acting on the building and its own dead load weight forces. Curtain walling is a vertical building enclosure which supports no load other than its own weight and the environmental forces which act upon it. Curtain walls are not intended to assist in maintaining the structural integrity of a building. Dead loads and live loads are thus not intended to be transferred via the curtain wall to t he foundations. METHOD
OF CONSTRUCTION
Curtain wall systems must be designed to handle all loads imposed on it as well as keep air and water from penetrating the building env elope. There are two basic types of curtain walling installations: stick and unitized. Stick systems are installed on site, component by component, after being prepared and machined in the factory and supplied in knock down form. They get their name from the fact that the vertical structural mullions (sticks) are fixed first. After the mullions are secure, the horizontal transoms are added and then the glazing panels, spandrels and vents installed in the completed grid; normally using a pressure plate and face cap. Stick systems are economical and, if correctly designed, detailed and installed, extremely reliable. They are however, slow to assemble, which may not suit certain fast track projects. 19
Unitized curtain walling systems are installed as a series of factory-assembled frames, usually with interlocking mullions and transoms. Unitized systems are used where the movement or deflections in a building are such that a stick system is inappropriate. Their principal benefits are speed of installation, minimal on site labour, and lower installation costs. Unitized systems are popular because they eliminate, or reduce, the need for onsite sealing, therefore making them less reliant on the standard of site workmanship. In conclusion, unitized systems offer the benefits of factory fabrication in controlled environment, and very rapid assembly on site. However, they are generally more expensive than stick systems and require longer lead limes. USAGE
It (glass block) used to generate a curved block wall.
It is used for residential cornice with den tiles.
It can be used to represent many block walls.
Provide the necessary resistance to penetration by the e lements.
Have sufficient strength to carry own self weight and provide resistance to both negative and positive wind pressures.
Provide an acceptable degree of fire resistance.
Provide the required degree of sound and thermal insulation.
Provide for thermal and structural movements
SEQUENCE OF OPERATION
Prior to the middle of the nineteenth century, buildings were constructed with the exterior walls of the building (bearing walls, typically masonry) supporting the load of the entire structure. The development and widespread use of structural steel and later reinforced concrete allowed relatively small columns to support large loads and the exterior walls of buildings were no longer required for structural support. Some of the first curtain walls were made with steel mullions and the plate glass was attached to the mullions with asbestos or fiberglass modified glazing compound. Eventually silicone sealants or glazing tape were substituted.
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DESIGN PRINCIPLES Weather tightness
It is the aim of every curtain walling installation to ensure total elimination of water ingress in accordance with the Building Regulations. This means that specifiers need a good awareness of the forces acting upon a building façade and the solutions available to ensure a weather tight exterior shell. While the façade can be designed to reduce the exposure of the walling elements, it is obviously impossible to eliminate wetting of the façade. The primary reason for this wetting is the complex action of the wind as it strikes a building. When the flow of air impacts on a building, the air flow is deflected across the surface of the façade causing changes in pressure. Curtain Walling Systems
There are three basic categories of curtain walling systems: front sealed, secondar y sealed and pressure equalized. Front sealed systems are designed to be totally impervious. They rely on exact positioning of the glazing panels and perfect mastic seals or glazing gaskets to provide a totally weather tight exterior shell. Essentially, front sealed systems are only appropriate for use on low rise buildings in sheltered locations, where the façade is likely to be changed within 10 years. Secondary sealed systems, as the name suggests, recognize that a 100% weather tight seal is unlikely to be achieved for the life of a façade. Thus, although designed to be weather tight, any water that does penetrate is collected and drained back to the outside through holes or slots. The final option is a pressure equalized curtain wall. In these systems an outer rainscreen provides a protective barrier. Protected Openings allow air ingress to a compartmentalized central cavity, which facilitates pressure equalization. Curtain Walling Installations
There are two basic types of curtain walling installations: stick and unitized. Stick systems are installed on site, component by component, after being prepared and machined in the factory and supplied in knock down form. They get their name from the fact that 21
the vertical structural mullions (sticks) are fixed first. After the mullions are secure, the horizontal transoms are added and then the glazing panels, spandrels and vents installed in the completed grid; normally using a pressure plate and face cap. In conclusion, stick systems are economical and, if correctly designed, detailed and installed, extremely reliable. They are; however, slow to assemble, which may not suit certain fast track projects. Unitized curtain walling systems are installed as a series of factory-assembled frames, usually with interlocking mullions and transoms. Unitized systems are used where the movement or deflections in a building are such that a stick system is inappropriate. Their principal benefits are speed of installation, minimal on site labour, and lower installation costs. Unitized systems are popular because they eliminate, or reduce, the need for onsite sealing, therefore making them less reliant on t he standard of site workmanship. ADVANTAGES
It provides a window frame construction on the exterior curtain wall which will accommodate and make fast the interior paneling on the inside of t he building.
Both the interior and exterior of the curtain wall construction can be fabricated from preformed panels.
Units are assembled & glazed under controlled shop conditions.
Full pressure equalization drainage system at each floor and accommodates building movements. DISADVANTAGES
Relies heavily on site workmanship and requires different trades men
Difficult to accommodate building movements
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Impossible to control water drainage to individual floor
Requires external access (scaffolding / gondolas)
Too many loose parts and component on site
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