External Walls PDF

External Walls Module Leader: Graham Terry External Walls Learning Outcomes At the end of this session you should be able to: Understand what are bricks Understand what are blocks Understand what are solid walls Understand what are cavity walls Understand what are wall details Under...

External Walls Module Leader: Graham Terry External Walls Learning Outcomes At the end of this session you should be able to: Understand what are bricks Understand what are blocks Understand what are solid walls Understand what are cavity walls Understand what are wall details Understand what is thin joint masonry Understand what is heat loss Foundations: Building Regulations  Clay Bricks (BS EN 771-1) Made using a combination of clay and shale to achieve required colour that is dried in a kiln Wide range of colours and textures 8  Types of Clay Bricks Common Ordinary bricks which are not designed to provide a good finished appearance or high strength. Cheapest brick. Facing Used due to their attractive appearance. In UK, fall into two main categories: Pressed Bricks – or Flettons: 60% of all production Wire-cut Bricks – often have one textured (usable) face: 30% of all production Engineering Designed primarily for strength and durability. Types of Clay Bricks Calcium Silicate (Sand Lime) Bricks (BS 187) Made by blending finely ground sand or flint and lime in approximate ratio of 10:1 Main properties of calcium silicate bricks High degree of regularity Wide range of colours 11 Types of Block Dense blocks Made from cement, sand and crushed gravel. Provide good sound insulation and are ideal in party walls and load bearing partitions (must be at least 75mm thick). Lightweight blocks Made from lightweight aggregates Provide good thermal insulation. 12 Block Sizes Blocks are equivalent to 6 bricks (3 high and 2 long) Standard block size is 440 x 215 x 100mm thick. 13  Durability Almost all durability problems are associated with moisture penetration Three main types:- Frost Damage:- freezing of water below the surface of the brick Bricks with coarse pore structure are generally more frost resistance than those with a fine pore structure Example of Frost Damage Typical Frost Damage on Soft Red Bricks 15 Example of Efflorescence Typical Surface Staining of Efflorescence 16 Example of Rising Dampness Rendered wall damaged by rising damp above brick plinth 17 Brickwork Terminology  External Walls The most common type is a cavity wall which consists of an outer skin of brick and an inner skin of block with thermal insulation in the cavity Performance requirements of external walls Stability Moisture resistance Sound insulation Thermal insulation Fire resistance. External Walls Stability of walls Type of material used Construction of the wall Design of the wall – slenderness ratio Stiffness of the wall – piers, buttresses, lateral restraint Type of load. http://www.bing.com/videos/search?q=cavity%ee%80%81+wall+%ee%80%80yout ube&qpvt=cavity%ee%80%81+wall+%ee%80%80youtube&view=detail&mid=BB8A 56C3B831D4684ECEBB8A56C3B831D4684ECE&FORM=VRDGAR 20 External Walls 26  Solid walls - English Bond Wall 1 brick thick This is English Bond. Notice the headers in one course, stretchers in the next. The queen closer keeps the bond. 29  English Bond examples On the right there are two examples of English bond. The lower one shows very dense engineering bricks - often found in factories and bridges etc. Make sure you understand the need for the queen closers (left). 30  English Bond - Thick walls High buildings need thicker walls. English Bond can easily be adapted. The right-hand picture shows two courses of a wall which is two-bricks thick. 31  English Bond - Garden Wall Bond English Bond is slow to lay. Work is quicker if the number of headers is reduced. This is why Garden wall bonds are so popular. On the right you should be able to see that there are three courses of stretchers to every one of headers. The number of bricks is virtually the same -it’s just quicker to lay stretchers and fewer bricks are rejected if they are too long or too short. 32 Solid walls - Flemish Bond This is Flemish Bond. Notice the headers and stretchers alternate in each course. Again, the queen closers keeps the bond. 33  Flemish Bond - examples Here are three examples of Flemish bond. Good quality housing from the Georgian and Victorian periods is usually in Flemish bond. 34  Flemish Garden Wall bond Flemish Garden Wall bond is quite rare but it does exist. The example on the right shows two stretchers in each course followed by a single header. There are other variations. 35 Joints  Early Cavity walls - c1920 Elevation DPC Wall ties This is a cavity wall in Stretcher Bond. It’s made from two leaves, or skins, of brickwork, each a half- brick thick. The internal leaf was Wall 250mm or 10 inches usually built from commons rather thick than facings. http://www.bing.com/videos/search?q=cavity%e e%80%81+wall+%ee%80%80youtube&qpvt=c avity%ee%80%81+wall+%ee%80%80youtube &view=detail&mid=BCD04CB9339D31E4D173 BCD04CB9339D31E4D173&FORM=VRDGAR  Early Cavity walls - c1930 DPC Wall ties By the 1930s, or so, some internal leaves were being built in blockwork. This was cheaper than brickwork. A standard block is 3 bricks high. Blocks were made from a variety of aggregates, some of them no longer available.  Cavity walls - c1960s and 1970s Lightweight blocks were originally made from lightweight aggregates such as clinker or pumice. These were slowly replaced with aerated concrete blocks such as Celcon and Thermalite. By the 1970s, or so, very little had changed. Cavity walls were still basically brickwork in the external leaf and blockwork in the internal leaf. However, lightweight blocks were becoming the norm to provide improved thermal insulation.  Modern cavity walls There are a number of ways in which modern ‘U’ Value requirements can be achieved (all use lightweight blocks)... Wall ties Should be spaced at 900 mm centres horizontally and 450 mm vertically in a staggered arrangement Closer spacing required around window and door openings 41 Early Jamb detail 44 Later Jamb detail Sill detail Thin joint masonry This is a fast-build method that allows the rapid construction of blockwork - with the potential for better quality construction - enabling early commencement of the finishing trades System comprises dimensionally accurate blocks used in conjunction with a quick-setting thin bed mortar Typically, a house can be completed ready for roofing in five to six days compared to the four to six weeks required with conventional construction methods. Thin joint masonry http://www.bing.com/videos/search?q=thin+joint+blockwork+disadvantages &&view=detail&mid=CA121338B7F57F5506B9CA121338B7F57F5506B9& FORM=VRDGAR 48  External Walls – Timber Frame Construction Fast construction Good quality control On site construction is reduced because of prefabrication Less dependence on traditional ‘wet’ skills Reduced dead-load Good thermal insulation http://www.bing.com/videos/search?q=timber+frame+wall+panels%ee%80%80&&view=detail&mid=4F9AE9E6952D769C6D 4B4F9AE9E6952D769C6D4B&FORM=VRDGAR Timber Frame Wall Panels 54 Kingspan TEK Building System U-value 0.19 - 0.21 U-value 0.20 - 0.22 55 W/m²·K. W/m²·K. Kingspan TEK Building System (cont.) 56 U-value 0.20 - 0.22 W/m²·K U-value 0.20 - 0.22 W/m²·K Calculation of heat loss Heat losses from a building can be classed as either a ‘fabric loss’ or a ‘ventilation loss’. 57 Fabric heat loss This is caused by the transmission of heat through the materials of walls, roofs and floors Pf = U x A x Δt Where Pf = rate of fabric heat loss = heat energy lost/time (W) U = U-value of the element considered (W/m2 K) A = area of that element (m2) Δt = difference between the temperatures assumed for the inside and outside environments (ºC)  Ventilation loss Ventilation heat loss from a building is caused by the loss of warm air and its replacement by air that is colder and has to be heated Pv = Cv x N x V x Δt 3600 where Pv = rate of ventilation heat loss = heat energy/time (W) Cv = volumetric specific heat capacity of air = specific heat capacity x density (J/m3 K) N = air infiltration rate for the room (the number of complete air changes per hour) V = volume of the room (m3) Δt = difference between the inside and outside air temperatures (0C)  Total heat loss Total heat loss = fabric heat loss + ventilation heat loss http://www.bing.com/videos/search?q=heat+loss&&view=detail&mid=693D1 5CBB03C98E04E65693D15CBB03C98E04E65&FORM=VRDGAR Total heat loss 61 What we have covered today To understand what are Bricks To understand what are Blocks To understand what are External walls To understand what is Bonding To understand what are Details To understand what is Thin joint masonry To understand what is Heat loss 68 Any questions