03 Project Execution & Control / Worked example

Function model of a concrete frame contractor

A concrete frame contractor sells a fixed promise before most of the information exists. It then turns information, materials, labour and reusable equipment into structure, floor by floor, on someone else’s site and programme, through safety hold points it cannot skip.

This IDEF0 model sets out what the business has to do to keep that promise. It is organised around one object, the pour, and built from operations science and public standards.

A reference model built from first principles. It is derived from queueing theory, the physics of concrete, contract economics and public standards. It does not describe or draw on any company’s management system. The legal register is a map, not legal advice.
Diagrams9context and two levels
Functions40seven stages, each broken down
Core objectThe pourevery function reads the same record
Input: transformedControl: governsOutput: producedMechanism: performs

Start at the context diagram. Select any box, or use the tree, to open the level below.

A-0

Frame contractor in context

Context diagram · parent none

Deliver in-situ concreteframes to a fixed promiseA0see A0I1 Enquiry & tender informationI2 Design information: drawings, specs, bar schedulesI3 Work areas released by the principal contractorI4 Materials: reinforcement, concrete, consumablesI5 Changes & instructionsC1 Contract terms & riskallocationC2 Safety law & temporaryworks standardsC3 Concrete executionstandardsC4 Principal contractor'sprogrammeC5 Payment & buildingsafety lawC6 Risk appetite &capacity limitsO1 Completed, accepted frameO2 As-built & quality recordsO3 Priced bidsO4 Applications, notices & final accountO5 State of every job: six state variablesM1 People: managers,engineers, gangsM2 Formwork, falsework &cranesM3 Supply chain: rebar,concrete, plantM4 Pour model: pour list &parameter table

Boundary arrows

  • I1 Enquiry & tender information
  • I2 Design information: drawings, specs, bar schedules
  • I3 Work areas released by the principal contractor
  • I4 Materials: reinforcement, concrete, consumables
  • I5 Changes & instructions
  • C1 Contract terms & risk allocation
  • C2 Safety law & temporary works standards
  • C3 Concrete execution standards
  • C4 Principal contractor's programme
  • C5 Payment & building safety law
  • C6 Risk appetite & capacity limits
  • O1 Completed, accepted frame
  • O2 As-built & quality records
  • O3 Priced bids
  • O4 Applications, notices & final account
  • O5 State of every job: six state variables
  • M1 People: managers, engineers, gangs
  • M2 Formwork, falsework & cranes
  • M3 Supply chain: rebar, concrete, plant
  • M4 Pour model: pour list & parameter table
A0

Deliver concrete frames

Level 1 decomposition · parent A-0

Price the promiseA1see A1Hold the promisebaselineA2see A2Design the flowA3see A3Make work readyA4see A4Build the pourA5see A5Measure the stateA6see A6LearnA7see A7I1 Enquiry & tender informationI2 Design information: drawings, specs, bar schedulesI2I3 Work areas released by the principal contractorI4 Materials: reinforcement, concrete, consumablesI5 Changes & instructionsC1 Contract terms & riskallocationC1C2 Safety law & temporaryworks standardsC2C3 Concrete executionstandardsC4 Principal contractor'sprogrammeC4C5 Payment & buildingsafety lawC5C6 Risk appetite &capacity limitsO1 Completed, accepted frameO2 As-built & quality recordsO3 Priced bidsO4 Applications, notices & final accountO5 State of every job: six state variablesM1 People: managers,engineers, gangsM1M1M1M2 Formwork, falsework &cranesM3 Supply chain: rebar,concrete, plantM4 Pour model: pour list &parameter tableM4M4M4Won contract & priced riskPour list & quantitiesBid assumptions & confidence levelPromise baseline: handover & information datesBaseline & deviation recordsFloor cycle, pour sequence & need datesConstraints outside our controlReady work: all constraints clearedEvents against the pourPour actuals: dates, hours, quantities, testsBottleneck load & work in progressOutturn against forecastUpdated parameter tableUpdated cycle, lead & strike timesRevised standards: methods & checks

Boundary arrows

  • I1 Enquiry & tender information
  • I2 Design information: drawings, specs, bar schedules
  • I3 Work areas released by the principal contractor
  • I4 Materials: reinforcement, concrete, consumables
  • I5 Changes & instructions
  • C1 Contract terms & risk allocation
  • C2 Safety law & temporary works standards
  • C3 Concrete execution standards
  • C4 Principal contractor's programme
  • C5 Payment & building safety law
  • C6 Risk appetite & capacity limits
  • O1 Completed, accepted frame
  • O2 As-built & quality records
  • O3 Priced bids
  • O4 Applications, notices & final account
  • O5 State of every job: six state variables
  • M1 People: managers, engineers, gangs
  • M2 Formwork, falsework & cranes
  • M3 Supply chain: rebar, concrete, plant
  • M4 Pour model: pour list & parameter table
A1

Price the promise

Level 2 decomposition · parent A0

Build the pour listA11Attach parameterdistributionsA12Simulate duration &costA13Apply the contracttermsA14Decide the bid &price at a statedconfidenceA15I1 Enquiry & tender informationI2 Design information: drawings, specs, bar schedulesC1 Contract terms & riskallocationC1C2 Risk appetite &capacity limitsO1 Priced bidsM1 People: managers,engineers, gangsM1M2 Pour model: pour list &parameter tableM2O2 Won contract & priced riskO3 Pour list & quantitiesO4 Bid assumptions & confidence levelC3 Updated parameter tableElement types to parameterisePour listProductivity, lead-time, strike & release-risk distributionsDuration & cost distributionsOutcomes the firm carries

Boundary arrows

  • I1 Enquiry & tender information
  • I2 Design information: drawings, specs, bar schedules
  • C1 Contract terms & risk allocation
  • C2 Risk appetite & capacity limits
  • C3 Updated parameter table
  • O1 Priced bids
  • O2 Won contract & priced risk
  • O3 Pour list & quantities
  • O4 Bid assumptions & confidence level
  • M1 People: managers, engineers, gangs
  • M2 Pour model: pour list & parameter table
A2

Hold the promise baseline

Level 2 decomposition · parent A0

Set the promisebaselineA21Record deviations asthey happenA22Serve notices withintime barsA23Value work & applyfor paymentA24Agree the finalaccountA25I1 Changes & instructionsC1 Contract terms & riskallocationC1C1C2 Principal contractor'sprogrammeC3 Payment & buildingsafety lawC3O1 Applications, notices & final accountO1O1M1 People: managers,engineers, gangsM1M2 Pour model: pour list &parameter tableM2I2 Won contract & priced riskO2 Promise baseline: handover & information datesO3 Baseline & deviation recordsI3 Constraints outside our controlI4 Events against the pourPromise baselineDeviation records with notice clocksPriced changeNotices servedValuations & unagreed change

Boundary arrows

  • I1 Changes & instructions
  • I2 Won contract & priced risk
  • I3 Constraints outside our control
  • I4 Events against the pour
  • C1 Contract terms & risk allocation
  • C2 Principal contractor's programme
  • C3 Payment & building safety law
  • O1 Applications, notices & final account
  • O2 Promise baseline: handover & information dates
  • O3 Baseline & deviation records
  • M1 People: managers, engineers, gangs
  • M2 Pour model: pour list & parameter table
A3

Design the flow

Level 2 decomposition · parent A0

Build the capacitystackA31Name & protect thebottleneckA32Set the floor cycle &work-in-progress capA33Derive pour sequence& need datesA34C1 Safety law & temporaryworks standardsC2 Principal contractor'sprogrammeM1 People: managers,engineers, gangsM1I1 Pour list & quantitiesC3 Promise baseline:handover & information datesO1 Floor cycle, pour sequence & need datesC4 Bottleneck load & workin progressC5 Updated cycle, lead &strike timesLimits: form sets, hook time, rebar supply, gangs, strike timeCapacity stackPour list by zoneNamed bottleneck, loaded to 85% or lessFloor cycle & work-in-progress cap

Boundary arrows

  • I1 Pour list & quantities
  • C1 Safety law & temporary works standards
  • C2 Principal contractor's programme
  • C3 Promise baseline: handover & information dates
  • C4 Bottleneck load & work in progress
  • C5 Updated cycle, lead & strike times
  • O1 Floor cycle, pour sequence & need dates
  • M1 People: managers, engineers, gangs
A4

Make work ready

Level 2 decomposition · parent A0

Screen the look-aheadfor constraintsA41Pull information toneed datesA42Call off materials bypourA43Line up crews &equipmentA44Commit the weeklyplanA45I1 Design information: drawings, specs, bar schedulesI2 Work areas released by the principal contractorM1 Supply chain: rebar,concrete, plantM1C1 Floor cycle, poursequence & need datesO1 Constraints outside our controlO2 Ready work: all constraints clearedInformation constraints & due datesMaterial call-off datesCrew & equipment needsNo pour starts unless all constraints are clearedChecked informationMaterials confirmed for the pourCrews & equipment confirmed

Boundary arrows

  • I1 Design information: drawings, specs, bar schedules
  • I2 Work areas released by the principal contractor
  • C1 Floor cycle, pour sequence & need dates
  • O1 Constraints outside our control
  • O2 Ready work: all constraints cleared
  • M1 Supply chain: rebar, concrete, plant
A5

Build the pour

Level 2 decomposition · parent A0

Erect formwork &falseworkA51Fix reinforcement &embedsA52Inspect & release thepourA53Place, finish & cureconcreteA54Confirm strikestrength & strikeA55Record the pourA56I1 Materials: reinforcement, concrete, consumablesI1C1 Safety law & temporaryworks standardsC1C2 Concrete executionstandardsC2C2C3 Payment & buildingsafety lawO1 Completed, accepted frameO2 As-built & quality recordsM1 People: managers,engineers, gangsM1M1M2 Formwork, falsework &cranesM2I2 Ready work: all constraints clearedO3 Events against the pourO4 Pour actuals: dates, hours, quantities, testsC4 Revised standards:methods & checksChecked deck & forms, permit to loadFixed reinforcementPre-pour hold point releasedInspection recordCast elementPour data: volume, mix, times, testsMaturity readings & permit to strike

Boundary arrows

  • I1 Materials: reinforcement, concrete, consumables
  • I2 Ready work: all constraints cleared
  • C1 Safety law & temporary works standards
  • C2 Concrete execution standards
  • C3 Payment & building safety law
  • C4 Revised standards: methods & checks
  • O1 Completed, accepted frame
  • O2 As-built & quality records
  • O3 Events against the pour
  • O4 Pour actuals: dates, hours, quantities, tests
  • M1 People: managers, engineers, gangs
  • M2 Formwork, falsework & cranes
A6

Measure the state

Level 2 decomposition · parent A0

Capture feeds by pourA61Compute the six statevariablesA62Forecast marginagainst the promiseA63Monitor flow & flagreal changeA64O1 State of every job: six state variablesM1 Pour model: pour list &parameter tableM1C1 Baseline & deviationrecordsI1 Pour actuals: dates, hours, quantities, testsO2 Bottleneck load & work in progressO3 Outturn against forecast( )Measure definitions( )Measure definitions( )Measure definitionsHours, pour records & deliveries coded to pourEarned value & cost by resourceCycle-time distribution & bottleneck load

Boundary arrows

  • I1 Pour actuals: dates, hours, quantities, tests
  • C1 Baseline & deviation records
  • O1 State of every job: six state variables
  • O2 Bottleneck load & work in progress
  • O3 Outturn against forecast
  • M1 Pour model: pour list & parameter table
A7

Learn

Level 2 decomposition · parent A0

Update parametersfrom outturnA71Score forecast errorA72Review each floorcycleA73Change a standard &test its effectA74M1 Pour model: pour list &parameter tableC1 Bid assumptions &confidence levelI1 Outturn against forecastI1I1O1 Updated parameter tableO2 Updated cycle, lead & strike timesO3 Revised standards: methods & checks( )Updating rules: priors,pooling, process control( )End of each floor cycleUpdated parameter estimatesParameter trends to test changes againstProposed changes to methods & checks

Boundary arrows

  • I1 Outturn against forecast
  • C1 Bid assumptions & confidence level
  • O1 Updated parameter table
  • O2 Updated cycle, lead & strike times
  • O3 Revised standards: methods & checks
  • M1 Pour model: pour list & parameter table
The principles

Why the model looks like this

Margin has three sources of risk. The price was a guess made before the information existed. Work on site loses flow in ways the firm controls. And the site, the design or the programme is released late, which the firm does not control. The model has a stage for each: price the distribution (A1), control the flow (A3 to A5), and hold the baseline so late release is recorded and recovered (A2).

The floor cycle is set by its slowest resource. Form sets, crane hook time, reinforcement supply, gangs and the time concrete needs to reach strike strength form a capacity stack. The largest term is the bottleneck, and improving anything else does not shorten the cycle [1][2]. Strike time is measured with the maturity method rather than assumed [5].

Readiness multiplies. A pour needs information, materials, labour, equipment, space, the work before it and permission, all at once. If each is 95% reliable, all seven are ready only about 70% of the time. So readiness is checked constraint by constraint, weeks ahead (A4) [7].

Queues grow fast near full load. Work in progress equals throughput times cycle time [3], and waiting rises steeply as utilisation approaches 100% [4]. That is why the model caps work in progress and loads the bottleneck to about 85%.

Six numbers describe the business. Promise, readiness, flow, money, integrity and knowledge. The last is the one most firms lack: the firm is learning if its forecast error for productivity, lead times and strike times is falling (A6, A7).

Control laws

Eight rules that follow

  1. No pour starts unless it is ready. Work without every constraint cleared does not enter next week's plan.
  2. Protect the bottleneck. It is never starved of ready work and never blocked by the work after it.
  3. Cap work in progress. Open floors and stacked trades are limited, so cycle time and temporary works on hire stay bounded.
  4. Load the bottleneck to about 85% or less. Above that, small disturbances cause long queues.
  5. Hold points are fixed. Speed up the information that feeds a check, never the check itself.
  6. Record every deviation when it happens, against the pour and the baseline, with its notice clock running.
  7. Every outturn updates a parameter. Nothing is measured without feeding back into planning and pricing.
  8. Price the distribution, not the point. The bid states its confidence level.
Law and standards register

Each instrument is mapped to the functions it governs. Check the primary text before relying on it.

InstrumentWhat it requiresGovernsStatus
C2 Safety law & temporary works standards
Health and Safety at Work etc. Act 1974General duties to employees and to others affected by the workA51 A55In force
Construction (Design and Management) Regulations 2015Contractor duties to plan, manage and monitor their own work; site induction; information to workersA31 A51 A53In force
Work at Height Regulations 2005Plan, supervise and carry out work at height safely: deck edges, falsework, strikingA51 A55In force
Lifting Operations and Lifting Equipment Regulations 1998Lifts planned by a competent person and supervised; lifting equipment thoroughly examinedA44 A51In force
BS 5975, temporary works procedures and falseworkTemporary works co-ordination, design check category, permit to load and permit to strikeA31 A51 A55Standard
C3 Concrete execution standards
BS EN 13670, execution of concrete structuresExecution classes, inspection, placing, curing and tolerancesA52 A53 A54Standard
ASTM C1074, maturity methodEstimating in-place strength from temperature and time, so strike time is measured rather than assumedA55Standard
C5 Payment & building safety law
Housing Grants, Construction and Regeneration Act 1996, Part II (as amended)Payment notices, pay less notices, adjudication and the right to suspend, up and down the chainA23 A24In force
Building Safety Act 2022 and regulations made under itCompetence, compliance and record duties, including the golden thread on higher-risk buildingsA56In force
Sources
  1. Hopp, W.J. and Spearman, M.L. Factory Physics. McGraw-Hill, 3rd ed. 2008.
  2. Goldratt, E.M. and Cox, J. The Goal. North River Press, 1984.
  3. Little, J.D.C. (1961) “A proof for the queuing formula L = λW”. Operations Research 9(3), 383-387.
  4. Kingman, J.F.C. (1961) “The single server queue in heavy traffic”. Proc. Cambridge Philosophical Society 57(4), 902-904.
  5. ASTM C1074, Standard Practice for Estimating Concrete Strength by the Maturity Method.
  6. BS 5975, temporary works procedures and falsework; BS EN 13670, execution of concrete structures.
  7. Ballard, G. (2000) The Last Planner System of Production Control. PhD thesis, University of Birmingham.
Next step

We use this model to review how a contractor plans, controls and learns, and to specify the systems that support it. Discuss a delivery control review →