Thursday, September 15, 2011

Wood free arches replacing door and window frames for shelters.


Wood free arches of SEVAI School building
SEVAI cost effective building technology centre has undertaken random rubble foundation, load bearing bricklaying without plastering and arches in the areas of doors and windows.SEVAI Technology centre Director Dr.K.Govindaraju trained the masons in Arch construction and he spoke in a training session regarding arch making. He further added, “Making a success of a ringed arch depends on careful preparation and planning before the actual building takes place. This involves drawing a plan of the arch on paper and then using this both to calculate the amount of materials you need and to plan construction of a timber former. Once the former is built, you place it under the arch to support the bricks during building. Start by drawing a life-size plan of the intrados arc on a large piece of paper or card. Measure across the springing line at the top of the opening, then go to the paper and draw a line of the same dimension across the bottom of the sheet. Mark the midpoint of the line carefully and this will give you the striking point of the arch. With this, the base line of the arch, marked, use the striking point as a center and draw a semi circle above the springing line with a large compass or a pencil tied to the end of a piece of string. Then lay a square or protractor along the springing line and draw a line up from the striking point which bisects the half circle. This gives the exact position of the key brick. Use the half circle and the perpendicular line running up through it to mark the position of each brick on the plan. Make sure all the bricks face inwards towards the striking point and that they are separated by neat, wedge shaped joints. To help keep the arch brickwork level with the face of the wall, nail four flat boards about 500mm long on each side of the opening extending from the top to the bottom of the arch. Then attach a string across the bottom of each pair of boards to act as a guiding line, this can be moved up as building progresses. Once the plan is drawn out (using one or more rows of brick) it can be used to calculate the exact number of bricks needed to complete the job. Remember, though, that the total has to be doubled in a cavity or double thickness wall where the arch has to be reproduced on both sides of a door or window opening”. -Govin

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