1. Weather and Contingency Allowance
Two approaches for assignment of weather allowance:
1. Add the Weather Allowance at the end of the project as a separate activity.
2. Add Weather Allowance to those affected by the weather.

2. * Can add weather allowance at the end of each construction segment ( site preparation, foundation…etc. )
* Other contingency items.
-- Procurement Allowance
-- Strikes
Time Zero
The close of the work period immediately preceding the start of the project.

3. Scheduling Computations for Arrow Diagram
Four time values associated with each activity:
1. ESD Early start date
2. EFD Early finish date
3. LSD Late start date
4. LFD Late finish date

4. Early Start Date for an activity is the earliest point in time that any activity bursting from its beginning node can start.
Late Finish Date is the latest point in time that any activity which merges at the activity’s ending node can finish.

5. Types of Activities 1. Production Activities
Those that can be taken directly from plans and specifications
2. Procurement Activities
Procurement of material and equipment
3. Management Decision Activities
Activities that can be created by management to avoid certain situations
- Delay Concrete
- Company Vacation

6. Precedence Diagram Advantages of Using Precedence Diagram
1. No dummy activity are required
2. A single number can be assigned to
identify each activity.
3. Analytical solution is simpler.

7. Same concepts used in Arrow diagram
* Numbering System
Same concepts used in Arrow diagram
Even or odd or in fives or tens
Smaller numbers to the left
Each Activity has its unique number.

8. Constructing the Precedence Diagram
1. Create Activity list and eliminate
redundancies.
2. Construct Rough Diagram “ Ball of
string”
Activities with no dependencies arranged at the left.
Create dummy start if you have more than one start “ Contract Award”
Ball-of-string provides a mean to determine sequence steps for each activity.

9. Constructing the Precedence Diagram (cont.)
3. Arrange Activities in a sequential order
Start by first activity “Contract Award”
Possible sequence step are those activities located at the arrow head

10. Estimating Activity Duration
Time Interval
Time Interval is selected according to the nature of the activity (seconds - minutes…)
It is common practice in construction industry to use calendar day.
Use one and only one time unit for any schedule.

11. Estimating Activity Duration
1. From Company’s Record
2. From Standard Estimating Guide
3. Interviewing Field Personnel.