- Collect the building materials
- Prepare the garage roof for building upon
- Build the bedroom walls
- Fit the bedroom window
- Add the roof
- Collect the interior furnishings
- Fit the electrics
- Plaster the walls
- Lay down the carpet
- Order the interior wallpaper and paint (which includes delivery time to the store and 1 hour for collection)
- Paper the walls
- Paint the ceiling
- Construct the cupboards
- Construct the wardrobes
- Construct the bed
- Add the furniture
- Add the final features to the bedroom (curtains, television etc.)
Here is the table of activities which includes the duration of the activity and which activities need to be completed before that one starts. The duration of the activities is when there is only one person completing the job, if the job has more than one person completing it, the time will be less.
Now I can draw a network to show the order in which the activities can be completed. The dotted lines in the network show a ‘dummy activity’ which is used to maintain the precedence’s between activities.
After drawing the network, I can show the ‘Earliest Arrival Times’ which is the earliest time an activity can start due to the duration of previous activities. To find the earliest arrival times, you have to consider each activity that goes into the events.
Now that I have found the ‘Earliest Arrival Times’ I can conduct a backward pass to find the latest finishing times for each activity. By doing this, I will be able to find out the critical path. Critical events will be found when the earliest arrival time is equal to the latest finishing time.
From this I can see that the earliest completion time for the network is 58 working hours.
I now can find the critical path for my network. The critical events are –
These activities must start on their earliest start time to enable the job to be completed in the shortest time. If the activities do start at their earliest time, the network will give the best possible solution. The critical activities are as follows (shown in light green colour)
As not all of the activities need to begin at their earliest time, some activities can start a few hours after. The time that these activities can wait before beginning without causing the overall time to be lengthened is called a ‘float’. A ‘float’ is calculated by removing the earliest possible finish time from the latest finish time. Here is the list of activities with their float for each one. When an activity has no float, it is on the critical path.
Now that I have found the earliest start times, latest finishing times and floats, I can draw a cascade chart. This cascade chart will be for when one person is doing all the activities.
I am confident that the solution to the problem of building an extended bedroom on top of a garage is correct and that I have found a unique and optimum solution to the problem. The only way the task could have been completed with the 58 hour time using 2 people would have been if one of the two workers had been able to fit the electrics but neither of them had the abilities to do so which meant an electrician had to be hired causing 3 people to be the minimum amount to complete the job. The refinement of hiring an electrician did not affect the 58 time requirement so it didn’t make much difference to the final solution but it did mean hiring an extra person for the 8 hours it took for the one electrician to complete their activity.
The optimum solution has some margin for error as many of the activities didn’t need to start at their start time and could have started a few hours late and still be able to meet the 58 hour target with 3 workers. Minor problems could have occurred and the final solution could still have been met as long as all of the activities on the critical path started at their earliest start time and ended at their earliest finish time. If an error occurred during an activity on the critical path, the optimal solution would not be able to be met.
The final solution is as accurate as possible but it is impossible to predict things that could happen so the networks and charts may be inaccurate as you cannot predict the future. For example, there could be extremely bad weather (which is a possibility living in England as the weather is entirely unpredictable) which could stop the builders erecting the walls and building the roof as this would cause a delay in proceedings. If something like this happened, the overall time would be lengthened by the initial length of the delay. The solution is as accurate as it can possibly be as we cannot predict any problems that could occur. If everything went to plan, the job of building and decorating a new bedroom above a garage should take place with 58 hours of labour needing 2 full-time workers and an electrician for 8 hours which gives a total of needing 3 workers to complete the task in 58 hours.