LINE OF BALANCE (LOB)
Miguel CABEZUDO
Nicolas LAFLESSELLE
DEFINITION
 A line of balance diagram comprises a series of
inclined lines which represent the rate of working
between repetitive operations in a construction
sequence.
 It's the best planning method for a repetitive work
such as a housing.
 It's a visual display of the rate of working of different
activities on a program.
PRINCIPLES
A
B
LOGIC DIAGRAM
C
LOB DIAGRAM
WITH A NON-PARALLEL WORKING
Buffer
A
B
C
Overall duration
Number
of units
Activity B slower than A
Activity C slower than B
Duration
Minimum Buffers
LOB DIAGRAM
WITH A PARALLEL WORKING / IDEAL RELATIONSHIP
A
B
C
Overall duration
Number
of units
Same rate of construction
Duration
Minimum Buffer
PRINCIPLES
B
A
D
C
LOGIC DIAGRAM FOR SEQUENCE
LOB DIAGRAM
OPERATION B AND C BEGINNING TOGETHER
A
B
C
D
Overall duration
Number
of units
Duration
LOB DIAGRAM
OPERATIONS B AND C ENDING TOGETHER
A
B.C
D
Overall duration
Number
of units
Duration
EXAMPLE – Access Deck Project
 Operation 1 : Install piles – 2 days (gang of 3 labours)
 Operation 2 : In situ beams– 4 days (gang of 4 carpenters)
 Operation 3 : Precast concrete deck – 1 day (gang of 2 labours)
EXAMPLE – Access Deck Project
Install piles
1
2 days
In situ beams
2
4 days
Precast deck
3
LOGIC DIAGRAM
1 day
4
EXAMPLE – Access Deck Project
Buffer
6
Piling
10
12
In situ
beams
23
27 28 29
Precast
deck
5
Completion
day 29
4
Bay
number 3
2
1
0
2
4
Buffer
6
8 10 12 14 16 18 20 22 24 26 28 30 32 34 36
Duration (days)
EXAMPLE – Access Deck Project
LABOUR RESOURCES
7
6
Pile caps/beams
5
Deck
Labour 4
3
2
Pile caps/beams
Piling
Deck
1
0
0
2
4
6
8 10 12 14 16 18 20 22 24 26 28 30 32 34 36
Duration (days)
EXAMPLE – Access Deck Project
6
Piling
5
4
In situ
Buffer
beams
10 12 13
17 18 19
Precast
deck
Completion
day 19
Bay
number 3
2
1
0
2
4
Buffer
6
8 10 12 14 16 18 20 22 24 26 28 30 32 34 36
Duration (days)
EXAMPLE – Access Deck Project
REVISED LABOUR RESOURCES
12
11
10
9
Labour 8
7
6
5
4
3
2
1
0
Caps and
beams Gang 2
Deck
Caps and beams
Gang 1
Piling
0
2
4
6
Deck
8 10 12 14 16 18 20 22 24 26 28 30 32 34 36
Duration (days)
EXAMPLE
CONSTRUCTION OF 10 HOUSES (5 CONSTRUCTION
OPERATIONS)
Operation
Duration per unit in weeks
Number of gangs
Foundations
2
2
External walls
4
3
Roof construction
1
1
Internal finishes
4
3
External works
2
2
NUMBER OF UNITS : 10
CONSTRUCTION OF 10 HOUSES (5
CONSTRUCTION OPERATIONS)
Foundations
1
2
External
walls
Internal
walls
Roof
3
4
SEQUENCE LOGIC FOR
OPERATIONS
External
works
5
6
CONSTRUCTION OF 10 HOUSES (5
CONSTRUCTION OPERATIONS)
Number of unit less 1 x duration of operation
Number of gangs used
Foundations :
Start unit 1 : week 0
Finish unit 1 : week 2 (2 weeks duration)
Start of unit 10 = 0 + (10 units – 1) x 2 = 18/2 = week 9
2 gangs
Finish of unit 10 = week 9 + 2 weeks = week 11
CONSTRUCTION OF 10 HOUSES (5
CONSTRUCTION OPERATIONS)
Foundations
9 11
10
Number
of houses
units
1
0
2
4
6
8 10 12 14 16 18 20
Duration (weeks)
CONSTRUCTION OF 10 HOUSES (5
CONSTRUCTION OPERATIONS)
External walls :
Duration per unit : 4 weeks
Number of gangs : 3
We need to consider the rate of construction between
the 2 operations :
Slope of the fondation balance line =
duration
=1
Number of gangs
Slope of the external walls balance line = 1.33
CONSTRUCTION OF 10 HOUSES (5
CONSTRUCTION OPERATIONS)
External walls :
Duration per unit : 4 weeks
Number of gangs : 3
Start unit 1 : week 2 + 1 week buffer = week 3
Finish unit 1 : week 3 + 4 weeks duration = week 7
Start of unit 10 = week 3 + (10 units – 1) x 4 = 3 + 36/3 = week 15
3 gangs
Finish of unit 10 = week 15 + 4 weeks = week 19
CONSTRUCTION OF 10 HOUSES (5
CONSTRUCTION OPERATIONS)
External
Foundations walls
9 11
15
19
10
Number
of houses
units
1
0
3
7
10 12 14 16 18 20
Duration (weeks)
CONSTRUCTION OF 10 HOUSES (5
CONSTRUCTION OPERATIONS)
Roof Construction :
Duration per unit : 1 week
Number of gangs : 1
Slope of the external walls balance line = 1.33
Slope of the Roof Construction balance line = 1
The relationship will begin at the finish of the external
walls balance line.
CONSTRUCTION OF 10 HOUSES (5
CONSTRUCTION OPERATIONS)
Roof Construction :
Duration per unit : 1 week
Number of gangs : 1
Start unit 10 : week 19 + 1 week buffer = week 20
Finish unit 10 : week 20 + 1 week duration = week 21
Start of unit 1 = week 20 - (10 units – 1) x 1 = 20 - 9 = week 11
1 gang
Finish of unit 1 = week 11 + 1 week duration = week 12
CONSTRUCTION OF 10 HOUSES (5
CONSTRUCTION OPERATIONS)
External
Foundations walls Roof
9 11
15 19 20 21
10
Number
of houses
units
1
0
3
7
11 12 14 16 18 20 22 24 26 28 30 32 34 36
Duration (weeks)
CONSTRUCTION OF 10 HOUSES (5
CONSTRUCTION OPERATIONS)
Internal walls :
Duration per unit : 4 weeks
Number of gangs : 3
External works :
Duration per unit : 2 weeks
Number of gangs : 2
CONSTRUCTION OF 10 HOUSES (5
CONSTRUCTION OPERATIONS)
External
Foundations walls Roof
9 11
15 19 20 21
10
Internal Internal
walls works
25
29 30 31
Number
of houses
units
1
0
3
7
11 12 13
17
21 23
26 28 30 32 34 36
Duration (weeks)
REFERENCES
 Cooke, Brian, & Williams, Peter. Construction,
planning, programming & control. Blackwell Publishing