FOUNDATION CERTIFICATE IN BUILDING CRAFT OCCUPATIONS UNIT 039 (01/00) Work Activity 2. Setting out buildings

Transcription

1 FOUNDATION CERTIFICATE IN BUILDING CRAFT OCCUPATIONS UNIT 039 (01/00) Setting Out Setting out buildings This activity looks at how buildings are set out on site and the methods of obtaining true dimensions, lines and levels. Outcomes By the end of this activity, students should be able to: choose and use tools and equipment for setting out buildings locate a given point on site from a scale drawing establish a datum point level off the datum set out corner pegs from the datum point to given sizes establish 90º angles using builder s square and/or 3:4:5 method check accuracy by measuring diagonals establish a builder s line to the required perimeter of a given building draw up a tool and equipment list 1

2 Marking out the site Delivery Presentation Show and describe the tools and equipment needed to mark out the shape of a building. Resources Pegs Clout nails Lump hammer Claw hammer Builder s line Spirit level Straightedge Measuring tapes Delivery Presentation On A4 paper draw a triangle with a base line of 40mm and other sides 30mm and 50mm. Show by protractor that the right angle is exactly 90º. Explain that this is a 3:4:5 triangle. Resources A4 paper Pair of compasses Ruler Protractor Pencils Student Activity Sheet 2A (see end of Work Activity Pack 2) Delivery Ask the students to: a) draw a 3:4:5 triangle using the same sizes and to measure each angle using a protractor. b) draw a 3:4:5 triangle with a 100 mm base (Students to work out the measurements of the other sides (75mm and 125mm). Measure and mark the angles. Presentation Explain how 3:4:5 can be used on larger areas. Set out a 3:4:5 triangle on a grassy surface using a base of 2 metres. Resources Pegs Lump hammer Nails Builder s line Tape measure H & S Risk assessment PPE overalls, safety footwear, gloves Student Activity Sheet 2B (see end of Work Activity Pack 2) Ask the students to mark out a 3:4:5 triangle with a 4 metres base. Check the right angle with a builder s square. 2

3 Marking out the site A block plan (see Work Plan 1) shows the position of a building relative to the boundaries or other fixed landmarks and also gives the overall sizes of the building. It is essential that the marking out of the building is in conformity with these measurements in every detail. In most cases the marking out of a site is done by driving pegs (stakes of wood) into the ground at all corners with the exact position of the corner shown by a nail driven partway into the top of the peg. A builder s line, pulled taut from nail to nail, shows the exact line of the external face of the wall. The equipment used comprises steel tape measures, 3 m and 30 m long, (linen tapes stretch), wooden pegs, builder s line, clout nails, lump hammer, and claw hammer. The pegs are usually square, approximately 450 mm x 50 mm x 50 mm, with one end sharpened to a point Temporary Peg for marking 3:4:5 ratio 3

4 Marking out the site (continued) Delivery Presentation Show how to mark out a rectangle 3 metres x 4 metres, using the 3:4:5 method. Show how to check by measuring diagonals. Resources Pegs Lump hammer Claw hammer Nails Builder s line 5 metres tape measure Student Activity Sheet 2C (see end of Work Activity Pack 2) Ask the students to mark out a rectangle 4 metres x 5 metres. Check measurements and diagonals. 4

5 Marking out the site (continued) Setting out right angles is important since a square or rectangle can easily become a rhombus or rhomboid. A right angle can be obtained by using a builder s square, which is a large, wooden construction, having one corner at 90º or by using the 3:4:5 method (Pythagoras Theorem). The string lines are marked respectively from the corner 3 units and 4 units. The distance on the diagonal (hypotenuse) should measure 5 units. If not, the pegs and lines should be moved until there is an exact measurement of 5 units. An alternative method of checking a square or rectangle is to measure the diagonals (corner to corner). The diagonals must be equal in length. 5

6 Levelling the tops of pegs Delivery Presentation Explain that when setting out buildings it is important to have the tops of the pegs level with each other otherwise accurate measurements cannot be made. Show an exaggerated slope on the chalk board to illustrate the difference between the horizontal lengths of the slope and the true horizontal. Explain and discuss the term datum and give a brief explanation of Bench Marks and how datum points are established. Student involvement Ask students how they would ensure that two pegs, 4 metres apart, were level. Response required: By using a spirit level and a straightedge. Delivery Presentation Choose an area of reasonably level ground, suitable for driving in pegs. Drive in peg 1 making sure that it is secure and that about 150mm of the peg is above ground level. Hammer a nail part way into the top of the peg. The top of the peg is now the datum from which all other pegs will be levelled. Measure 4 metres from the nail to the position of peg 2. Drive in peg 2 and then measure accurately the 4 metres and hammer a nail into the top of peg 2 at the 4 metres mark. Secure a taut line between the nails. Show that the pegs are too far apart to check for level using a spirit level and that the distance is longer than the straightedge. Student involvement Ask how they can level across using the spirit level and straightedge. Response required: Use an intermediate peg. Resources Pegs Lump hammer Claw hammer Nails Builder s line 5 metres tape measure 6

7 Levelling the tops of pegs The tops of the pegs must be level if accurate measurements, on plan, are to be obtained. When setting out on a sloping site discrepancies can occur unless the tops of the pegs are levelled. Distances between pegs are usually too far apart for a spirit level to span, even when a straightedge is used to increase the spread. The method here is to drive in a first stake at the exact position of a corner on the front line of the building. The corner should be at the higher point if there appears to be a slope. About 150 mm of the peg is left out of the ground and a nail is knocked in at the top of the peg in the exact position of the corner from the boundaries/landmarks. This peg is now the datum from which all other pegs will be levelled. A second peg is then driven in at the other corner of the front line and a nail located on the peg, the measured distances from boundary/landmark and peg 1. The builder s line is then pulled tight between the nails. Even with a small building it is unlikely that a straightedge (approximately 2 metres long), with a spirit level on top, would span the two pegs in order to level them. The method adopted is to drive in a temporary peg along the path of the line from peg 1, slightly less than the length of the straightedge. By using the straightedge and spirit level, the temporary peg is then hammered down until the bubble is level. This is repeated with other temporary pegs if necessary until peg 2 can be reached. This is levelled through and will then be at the same level as peg 1. The measurement between nails can then be checked and, where needed, the nail in peg 2 can be adjusted to the correct position. Temporary pegs can then be removed. Corner peg Spirit level Temporary intermediate peg Straight edge 7

8 Levelling the tops of pegs (continued) Delivery Presentation Lay the straightedge directly under the builder s line, with one end touching the datum peg. Hammer in another peg just short of the end of the straightedge. Place the straightedge on top of the pegs and then place the spirit level on top of the straightedge. Check the bubble and hammer down the intermediate peg until the bubble is level. Check for accuracy by reversing the spirit level. Repeat the process with other pegs until peg 2 is reached and levelled. Check that the distance between the nails on pegs 1 and 2 is correct. Resources Pegs Lump hammer Claw hammer Nails Builder s line 5 metres tape measure Student Activity Sheet 2D (see end of Work Activity Pack 2) Ask students to position two pegs exactly 5 metres apart. Assignment Sheet 2 (See end of Work Activity Pack 2) Provide an assignment sheet for each student requiring them to: a) set out an L shaped building to given distances from marked boundary lines. b) draw up a tool and equipment list for the setting out work. 8

9 Levelling the tops of pegs (continued) When setting out buildings on site it is usual to extend the lines beyond the corners to markers called profiles. A nail or saw cut is positioned on the profile where the extended line crosses it and then other nails or saw cuts are positioned to show the insides and the outsides of the foundation concrete and of the wall. Cross lines Cross lines nails Profile Corner peg This is because the corner peg will disappear when the foundations are being excavated. The corners of the brickwork can be plumbed down from the intersecting lines at the corner onto the top of the concrete strip foundation. 9

10 Student Activity 2A Delivery Resources Students to practice drawing triangles and measuring and marking angles. For each student: 2 A4 sheets of paper Pair of compasses Ruler Protractor Pencils 10

11 Activity Sheet 2A This activity is in two parts. Part 1 On an A4 sheet of blank paper draw a triangle using the 3:4:5 method, with a base line of 40 mm and the other sides 30 mm and 50 mm. Using a protractor, measure each angle and mark in the degrees (The three angles should total 180º). Part 2 On an A4 sheet of blank paper draw a 3:4:5 triangle with a base line of 100 mm. You will need to work out the lengths of the other two sides. Measure and mark the lengths of the other two sides and measure and mark each angle. When you have finished hand this to your teacher for marking. 11

12 Student Activity 2B Delivery Resources Students to practice setting out a right angle using the 3:4:5 method. For each student: 3 pegs 3 nails Lump hammer Claw hammer Builder s line Tape measure 5 metres 12

13 Activity Sheet 2B In this activity you will practise setting out a right angle, on a grassed area, using the 3:4:5 method. Mark out the right angle using pegs, nails, hammers, builder s line and a 5 metres tape measure. The base line of the triangle is to be 5 metres long. When you have marked out the right angle, check it using a builder s square. The teacher will check this piece of work. 13

14 Student Activity 2C Delivery Resources Students to mark out a rectangle 4 metres x 5 metres, checking the measurements and diagonals. For each student: 4 pegs 4 nails Lump hammer Claw hammer Builder s line Tape measure 5 metres and 30 metres 14

15 Activity Sheet 2C You have been provided with pegs, nails, hammers, builder s line and tape measures. Mark out a rectangle, 4 metres by 5 metres using the 3:4:5 method to obtain the right angles at each corner. Check the lengths of the diagonals to see how accurate you are. The teacher will check this piece of work. 15

16 Student Activity 2D Delivery Resources Students should position two pegs exactly 5 metres apart and to practice levelling the tops of pegs. For each student: 5 pegs 2 nails Lump hammer Claw hammer Builder s line Tape measure 5 metres 2 metres straight edge Spirit level 16

17 Activity Sheet 2D In this activity you will practise levelling the tops of pegs, using temporary pegs to level from the datum peg. You are asked to position two pegs exactly 5 metres apart. Set up one peg as the datum peg. Use the straightedge and spirit level to level off the datum. Use temporary pegs to cover the distance up to the other end peg 5 metres away. Check that the nails in the datum peg and the other end peg are exactly 5 metres apart. The teacher will check this piece of work. 17

18 Assignment 2 Delivery Resources Provide an assignment sheet for each student requiring them to set out an L shaped building to given distances from marked boundary lines, and to draw up a tool and equipment list for the setting out work. For each student: photocopy of Assignment Sheet 1 (see facing page) copy of drawing of L shaped building (See Appended Sheet at end of Section 9) pegs nails hammers club and claw builder s line 2 metres straightedge spirit level tape measures - 5 and 30 metres 18

19 Assignment Sheet No. 2 This assignment is in three parts. Part 1 A drawing has been given to you showing the size and shape of an L shaped building and its position from two boundary lines. Select the equipment you need and measure and mark out the building. Level all pegs from a datum peg. Check all sizes, right angles and diagonals before asking for your work to be assessed. Part 2 Write a list of all the tools and equipment that you needed for marking out the building. Part 3 After the setting out has been completed remove all tools and equipment. Clean pegs and tape measures and return them to the store. Clear up the site and dispose of any debris. Your completed work for this assignment should be handed in by: 19

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21 Assignment 2 Drawing of an L shaped building See Section 9 Appendix. 21

22 Enhancement Visit/s to building site/s to see setting out in progress. Identification of Ordnance Bench Marks (OBM) and Temporary Bench Marks (TBM) Under guidance, students should prepare an observation/question checklist prior to each visit. Key Skills IT observation/question list tool and equipment list Application of Number making calculations sizes - measuring Communication oral asking questions, seeking clarification, answering questions, taking part in discussions reading activity sheets, assignment sheet, obtaining information writing letters booking transport, assignment list of tools and equipment, visit notes 22

23 Student s Handbook Exercise 1 True or False 1. False 2. False 3. True 4. False 5. True 23

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