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  1. 1. PHASE 6 REVISION ANSWERS 1. Sulphate attack in mortar occurs when the soluble sulfate salts within some clay bricks react with a constituent (tricalcium aluminate) of the portland cement within mortar 2. (a)60 degree method (b) site formula method (half the span x half the span + rise ÷ rise (c) geometric setting out 3. (a) A smaller site area is required (b) Symmetrical section has a similar resistance to bending in both directions (c) The cavity is wide enough to accommodate services (d) Less vertical plumbing lines are required so the labour cost of the wall tends to be lower. 4. To reduce the power voltage from 230 to 110 V 5. The reason Rat Trap bond is used is it allows a brick wall to be reinforced internally while the facade of the wall remains untouched 6. The purpose of having a Camber in a Camber arch is to counteract the visual effect of the arch sagging. It is calculated by using a rise of 1mm for every 100mm of Span. 7. Building the Invert of a Bulls-Eye A 100 x 75mm timber strut is fixed temporarily on the brickwork either side of the arch spanning the opening. The striking point or centre of the bulls eye is then marked on the strut. It is essential the strut is well stabilised over the opening This ensures it is not going to move during the construction of the invert arch.
  2. 2. The trammel is usually cut from 44mm x 18mm timber. The distance between the striking point and the tip or point of the trammel is the outer radius of the bulls eye plus a 10mm mortar joint The trammel is then nailed to the striking point marked on the timber strut and should swing freely. It is essential to keep the surrounding brickwork accurately ranged and plumb on the face. This assists with ensuring the entire circumference of the bulls eye will align with the completed wall The invert is carefully cut to the required semi circular shape. Each brick is temporarily placed in position using wood spacers or a box rule to represent bed and cross joints. The curve is marked with a pencil held at the point of the trammel. The bricks (creepers) must then be perfectly cut to the required shape. When the creepers have been cut precisely to the mark they are then set into the wall It is essential to once again check for accuracy with the trammel. This process is repeated for each creeper until the invert has been completed. 8. 3.14 x (910 + 215 + 215) 1340 = 4208 ÷ 70 = 60 Voussoirs 9. To calculate this sum do the following........ One tile = .150 x .150 = .0225 Wall = 5.3 x 2.4 = 12.72 Divide 12.72 by .0225 = 566 Tiles excluding waste 566 x 110% = 623 Tiles including waste
  3. 3. 10. Setting out tiles When tiling a wall a level base must be established. If the tiling begins at some point over floor level - a level base for the tiles to sit onto can fl be easily created using a timber gauge batten that is fixed to the wall and correctly levelled. If the tiles begin at floor level its quite likely the floor is not perfectly level So in this case establish the lowest point of the floor lish Measure and mark the wall, one full tile height plus two grout joint widths up from this point Marking one full tile height plus two grout joint from the floor Using a spirit level to make sure it's perfectly level – nail the temporary gauge batten to il the wall with the top edge corresponding to the mark. This is the setting out or starting line. If it is required to finish at an exact height on the wall, in order to accommodate a border or shower height for example - work down the wall in multiples of the tile size plus joints. ork This gives the required level of the starting batten. Mark the centre of the wall on the batten and centering the first tile, set out a line of tiles to establish how they fit. Mark the final position (gauge) of each tile on the batten Using a plumb line or level create a vertical line on the wall – this should be created at the last full tile before the corner of the wall to be tiled wa 11. Unglazed Tiles must have 2-3 coats of protective oil (linceed or manufacturers 23 recommendations) applied when completely dry. They should then be coated with 2 2-3 layers of lacquer or glazing coat befor grouting takes place. 12. Pocket Reinforcement This reinforcement is contained in the rear of the wall. Pockets are left at the back of the brickwork to allow vertical sections of concrete to be poured around steel. This type of reinforcing is normally used in retaining walls
  4. 4. 13. Backdrop manholes (sometimes called cascade manholes) are used where one drain or sewer is to connect with another drain or sewer that is at a considerably lower level. The external backdrop is preferred as the internal causes obstruction when accessing the manhole – many local authorities will forbid internal backdrops for this reason 14. The workings of a septic tank can be seen in the following sketch 15. Pre stressed Concrete lintels advantages over cast in situ include. Arrive to site ready made They are generally slimline Usually easy to position by 1 or 2 people No delay in the work process Cheap and cost effective Guarenteed strength quality Can often accomodate greater loads 16. Cavity Wall Lintel for blockwork & Timber Frame construction
  5. 5. 17. Common Site Drawings include............ Block plans 1:1250 or 1:2500 Site plans 1:500 General location drawings 1:50 or 1:100 Component drawings 1:100 / 1:50 / 1:20 Detail drawings 1:10 / 1:5 / 1:1 Assembly drawings 1:20 / 1:10 / 1:5 or sometimes enlarged using scales such as 5:1 or 10:1 18. Reconstituted stone (also known as engineered stone) is a mixture of concrete and ground up natural stone that is combined with highly specialised polyester resin It is then cast into different shapes. Locations can include, Coin Stones. Window Cills, Lintels, Cappings, Mullion Posts, Paving etc. 19. Three ramps are...... Straight Ramp Convex Ramp Concave Ramp They are used to reduce or increase the height of a wall or simply as a decorative feature. 20. Drawing symbols for materials can be seen below.....