F-1 Applying Lean to Factory Homebuilding Dr. Mike Mullens, PE

F-2 Big Product with Many Large Components

F-3 Few Small, Fixed Workstations

F-4 Few Large, Fixed Workstations

F-5 Many Large, Moving Workstations Labor and materials flow to product while product flows continuously on line Little inventory because there is no space Line used to set pace and facilitate delivery of large components

F-6 Activity Location Flexibility Most operations after roof set can and do take place anywhere on line – as long as precedence's are met

F-7 Some Activities Can Stop the Line

F-8 Value Added Continuously: Often in Parallel Activities

F-9 Massive Work Content Multi-operator teams perform trade-focused activities

F-10 Massive Work Content Extended cycle times Very difficult to measure work content and cycle time for any unit Module Wall Length Wall Assembly Labor: Observed Man Minutes Estimated Cycle Time (Min) (Feet) Value Added Non Value Added Total 2528 A (89%) 27 (11%) 252 (100%) B (84%) 54 (16%) 348 (100%) 174 Sub Total (87%) 81 (13%) 600 (100%) A (85%) 48 (15%) 312 (100%) B (83%) 72 (17%) 420 (100%) 210 Sub Total (84%) 120 (16%) 732 (100%) 366 Total (85%) 201 (15%) 1332 (100%) 666

F-11 Product Built-to-Order: Varied Product Mix with Customization

F-12 Product Built-to-Order: Varied Product Mix with Customization

F-13 Product Built-to-Order: Varied Product Mix with Customization

F-14 Product Built-to-Order: Varied Product Mix with Customization

F-15 Product Built-to-Order: Varied Product Mix with Customization

F-16 Product Built-to-Order: Varied Product Mix with Customization

F-17 Product Built-to-Order: Varied Product Mix with Customization

F-18 Product Built-to-Order: Varied Product Mix with Customization High process variability High process variability

F-19 Module Wall Length (Feet) Wall Assembly Labor: Observed Man Minutes Estimated Cycle Time (Min) Value Added Non Value Added Total 2528 A (89%) 27 (11%) 252 (100%) B (84%) 54 (16%) 348 (100%) 174 Sub Total (87%) 81 (13%) 600 (100%) A (85%) 48 (15%) 312 (100%) B (83%) 72 (17%) 420 (100%) 210 Sub Total (84%) 120 (16%) 732 (100%) 366 Total (85%) 201 (15%) 1332 (100%) 666 Product Built-to-Order: Varied Product Mix with Customization High cycle time variability Very difficult to predict work content and cycle time for each activity Not easy to control line balance

F-20 Cycle vs. TAKT Time Average cycle time for each activity must be less than TAKT time Activity with largest average cycle time is bottleneck activity If bottleneck activity is delayed, line capacity is lost – can happen even if average cycle less than TAKT time

F-21 Seeing the Waste (and the Opportunity) Constant imbalance in labor & work content Production mistakes Design oversights Material shortages

F-22 Floating Bottlenecks: Imbalance in Labor and Work Content Upstream Queue - Floors

F-23 Floating Bottlenecks: Imbalance in Labor and Work Content Downstream line starvation – drywall finishing and interior finishing

F-24 Floating Bottlenecks: Imbalance in Labor and Work Content Other Impacts: –Hurry  exhaustion, frustration, rework –Overtime  higher costs, turnover –Unfinished work in yard –Lost production capacity

F-25 Value-Added vs. Non-Value Added Time Module Wall Length Observed Man Minutes Estimated Man Min (Feet) Value Added Non Value Added Total 2528 A (89%) 27 (11%) 252 (100%) 358 (142%) 2528 B (84%) 54 (16%) 348 (100%) 371 (106%) Sub Total (87%) 81 (13%) 600 (100%) 729 (122%) 2632 A (85%) 48 (15%) 312 (100%) 349 (112%) 2632 B (83%) 72 (17%) 420 (100%) 337 (80%) Sub Total (84%) 120 (16%) 732 (100%) 686 (94%) Total (85%) 201 (15%) 1332 (100%) 1415 (106%)

F-26 Operations Process Chart with Work Measurement

F-27 Non-Value Added Activities Task MAN MIN Tot. Man Min 2528 A 2528 B 2632 A 2632 B % Unknown Rebuild window subassembly Cut sheetrock for other workstation Helping roof jig Paper work Out of nails and glue Move modules on-line 884 Helping wall set 3474 Worker hurt by nailgun 774 Order sheetrock 774 Clean-up442 Moving pile of sheetrock 221 Carry bathtub to wall set area 221 Total:

F-28 Production Schedule

F-29 Avg. 8 weeks Production Cycle Times

F-30 Rework 44% Avg. = 7%

F-31 Rework Labor waste Service problems Line variability

F-32 Rework

F-33 Lean Construction Principles Keep activities flowing, particularly along critical path and bottleneck activities Remove uncertainty and variability, especially along critical path and bottleneck activities

F-34 Lean Construction Approach Improve quality of task assignments Be sure preceding activities are complete, task well documented, and materials and tools are available

F-35 Lean Construction Problem Mitigation Plan buffers – backlog of activities for crews (queues of work ready to be done – adding to length of critical path and thus to production line) Surge piles – raw and WIP materials Flexible capacity – intentionally underutilized crews or flexible use of cross-trained workers