Line of Balance in Construction
Line of Balance (LOB) is the oldest graphical method for scheduling repetitive work. Each trade becomes a sloped line whose slope is its production rate across identical units. Where lines cross, trades collide; where they converge, the downstream crew is about to run out of ready work. Developed at Goodyear in 1941 and formalised for construction by the US Navy in the 1950s, LOB is the direct ancestor of the Location-Based Management System and still the clearest single-page view of a repetitive project in production.
What is Line of Balance?
Line of Balance is a graphical scheduling method for repetitive construction work. Units of production (floors, kilometres, rooms) sit on the vertical axis and time on the horizontal. Each trade is plotted as a sloped line travelling through the units; the slope of each line is that trade's production rate. Line crossings, convergences and divergences are read as production conflicts, bottlenecks and under-utilisation.
Also known as: flowline scheduling, line-of-balance planning, repetitive scheduling method, LOB chart. The acronym LOB is standard across the construction scheduling literature.
How to read a Line of Balance chart
One LOB chart carries the information a hundred Gantt rows would need, so the chart has its own grammar. Four things to look for.
- 1
Slope = production rate
A steep line means fast work (many units per week); a shallow line means slow work. A perfectly vertical line would be an infinitely fast trade; a horizontal line means no progress at all.
- 2
Parallel lines = balanced flow
When all trades slope at similar angles, work flows smoothly from one trade to the next and buffer time stays constant. This is the state the project is trying to reach.
- 3
Crossing lines = collision
Two trades trying to be in the same unit at the same time. On site this becomes an argument about who waits for whom; on the chart it is a dot where plans intersect.
- 4
Converging lines = starved downstream crew
An upstream trade is slower than the trade immediately behind it. The downstream crew catches up, runs out of ready work, and either stops or breaks the flow by jumping ahead to work that is not actually clear. Diverging lines are the opposite problem: the downstream trade is slower, so finished units wait idle between crews and the programme stretches.
Worked example: balancing four trades on a 20-storey tower
A 20-storey residential tower, four trades through each floor: structure, MEP first-fix, partitions and fit-out. The initial plan assigns one crew to each trade with different production rates. The LOB view shows why the initial plan does not flow — and how to fix it by re-sizing crews.
| Trade | Crew size (initial) | Production rate | Chart signal |
|---|---|---|---|
| Structure | 1 crew | 1 floor per week | Baseline — all other trades sized against this |
| MEP first-fix | 1 crew | 0.75 floors per week | Line diverges — MEP falls behind structure by floor 8 |
| Partitions | 1 crew | 1.25 floors per week | Line converges toward MEP — crashes by floor 10 |
| Fit-out | 1 crew | 0.5 floors per week | Line falls further behind every week — handover slips |
What the chart tells the planner
The initial plan has three structural problems: MEP diverges from structure (downstream slower than upstream → completed floors queue up waiting for MEP and the gap grows every week); partitions converges on MEP (downstream faster than upstream → crashes around floor 10, where partitions arrives before MEP is clear); fit-out slopes shallower than everyone (progressively worse arrears → the whole project slips).
The balanced plan matches production rates: speed MEP up with a second crew (0.75 → 1.0), pace partitions down to match (1.25 → 1.0 by splitting the crew across two floors), add a second fit-out crew (0.5 → 1.0). All four trades now slope at 1 floor per week — the lines run parallel, no collisions, no starved crews, and handover arrives on schedule.
Where Line of Balance breaks down
LOB is a diagnostic tool first and a control system second. The four limitations below are why most mature lean programmes use LBMS or Takt rather than LOB alone.
Non-repetitive work
The method assumes identical units. A one-off commercial fit-out, a bespoke civic building, or a project where every floor has a different footprint gets nothing from LOB and should stay on CPM.
Production rates presented as fixed
Real crews speed up as they learn the floor and slow down when supply chains stutter. A static LOB chart implies constant rates and gives false confidence that the balance will hold. Modern LBMS tools address this with learning-curve adjustments; a hand-drawn LOB chart does not.
No weekly-commitment layer
LOB tells you the balanced plan but not whether the plan will actually hold next week. Without a lookahead and a PPC loop (the Last Planner System layer), chart balance degrades silently as real site failures accumulate.
Static artefact in a dynamic project
A printed LOB chart in the site office is accurate on the day it is drawn and progressively less so from week two. The chart lives or dies with the discipline to update it against actual field progress — the same discipline that LPS and modern Takt tools automate.
How VisiLean handles repetitive scheduling
VisiLean Planner runs the master schedule in CPM and layers Takt zones on top for repetitive work. The approach is adjacent to LOB rather than a direct implementation of it — the production rhythms LOB visualises as sloped lines become rhythmic Takt wagons flowing through zones, with the same underlying goal of balanced flow across identical units.
- CPM master imported directly from Primavera P6, Microsoft Project or Asta Powerproject — same source of truth across repetitive and one-off work.
- Takt zones layered on repetitive portions (floors, spans, rooms) so each trade has a defined rhythm through the zones, equivalent to the balanced-slope target an LOB chart identifies.
- The six-week lookahead screens upcoming zones for the constraints that typically break flow — materials, prerequisites, access — before the committing week.
- LiveSite progress updates from the field feed the schedule continuously, so planned-vs-actual drift is visible before it compounds into the lines-cross problem LOB diagnoses.
Related methods
LBMS — Location-Based Management
The modern mathematical descendant of LOB. Flowline charts, learning-curve adjustments and native integration with CPM masters.
Read moreTakt Planning
The production-control descendant of LOB. Zones, wagons and fixed Takt times replace sloped lines as the mechanism for balanced flow.
Read moreCritical Path Method
The master-schedule method LOB sits on top of in modern practice. CPM for the frame, LOB for the repetitive portions.
Read moreVisiLean Planner
The product that runs CPM, Takt and 4D BIM as views of the same schedule — including the repetitive-flow balancing LOB visualises.
Read moreFrequently asked questions
What is Line of Balance in construction?
Line of Balance (LOB) is a graphical scheduling method designed for repetitive work. Each trade is plotted as a sloped line whose slope represents the trade's production rate across identical units — floors in a high-rise, kilometres of pipe, hotel rooms, housing plots. Where two lines cross, two trades are trying to be in the same place at the same time; where the gap narrows, the downstream crew is about to run out of ready work; where it widens, finished units sit idle and the programme stretches. LOB came out of Goodyear's manufacturing operations in 1941 and was formalised for construction by the US Navy and the UK Ministry of Public Buildings and Works in the 1950s and 1960s.
How is Line of Balance different from a Gantt chart?
A Gantt chart shows every activity on its own row with time on the X-axis — fine for one-off work, dense and unreadable for repetitive work. LOB plots units of production (floor, span, kilometre) on the Y-axis and time on the X-axis, with each trade appearing as a single line that moves through all the units. One LOB chart replaces hundreds of Gantt rows for a high-rise tower and makes trade conflicts visible at a glance, which is exactly what a Gantt view hides.
When should a construction project use Line of Balance?
LOB is appropriate when the project has genuine repetition: multiple identical floors, apartment blocks, highway sections, pipeline kilometres, hospital wards or hotel rooms. The more units and the more similar they are, the more LOB earns its keep. Projects without real repetition — a one-off commercial fit-out, a bespoke civic building — gain nothing from LOB and should stay on CPM. On mixed projects, LOB is used for the repetitive portion and CPM for the rest, both feeding the same master programme.
What is the difference between Line of Balance and Takt planning?
Both target rhythmic flow across repetitive units, but they come at it from different directions. LOB is a diagnostic chart that reveals bottlenecks and lets planners re-size crews to balance production rates. Takt planning imposes a fixed rhythm (the Takt time) on the whole production system and sizes each zone of work to fit that rhythm — a more disciplined, more operational, more Lean-aligned method. In modern construction, LBMS (Location-Based Management System) is the mathematical descendant of LOB; Takt is the production-control descendant. Most mature Lean programmes use Takt and visualise with LBMS flowlines; standalone LOB is now relatively rare on new projects.
What software supports Line of Balance scheduling?
Tilos and Trimble Vico Office are the two platforms most strongly associated with LOB and flowline methods. Primavera P6 and Microsoft Project do not render true LOB views natively but can be exported to third-party tools. VisiLean's Planner uses CPM as the master and supports Takt zones for repetitive work directly — a different but closely related approach to the production-rate balancing that LOB offers.
See balanced flow on a live schedule
VisiLean runs CPM and Takt as views of the same schedule — the balanced-rate target an LOB chart identifies becomes a rhythm the field actually works to.