Exercise 7.3

Group Discussion  


What Survey methods are group members familiar with and what is used within these companies




Calculating areas


When a shape is drawn on a scaled grid you can find the area by counting the number of grid squares inside the shape.   

In this example there are 10 grid squares inside the rectangle.


In order to find an area value, using the grid method, we need to know the size that a grid square represents.


This example uses metres but the same method applies for any unit of length or distance.


You could, for example be using inches, metres, miles, feet etc.


In this example each grid square has a width of 1m and a height of 1m.


In other words each grid square is one 'square metre'


Counting squares on a grid to find the area works for all shapes – as long as the grid sizes are known. 


However, this method becomes more challenging when shapes do not fit the grid exactly or when you need to count fractions of grid squares.


In this example the square does not fit exactly onto the grid.


We can still calculate the area by counting grid squares.

  • There are 25 full grid squares (shaded in blue)
  • 10 half grid squares (shaded in yellow) – 10 half squares is the same as 5 full squares.
  • There is also 1 quarter square. (¼ or 0.25 of a whole square).
  • Add the whole squares and fractions together: 25 + 5 + 0.25 = 30.25.

The area of this square is therefore 30.25m2 .

You can also write this as 30¼m2.




Exercise 7.4


The Basics Calculating areas - using this Worksheet



Exercise 7.5


Using the Roofing Model, mesure and caculate the area of the roof covering, less rooflights, and plus any additional areas     The models are scale 1:76



























Estimating Pitched Roofing


Exercise 7.6

Use the area calculations above, prepare a simple estimate for replacement of each if the roofs with the similar roof covering.



Group Discussion


Exercise 7.7

What other items should be included in a comprehensive estimate?




Exercise 7.8

Using Manufacturer Software/App