With 70% of construction projects over budget and delivered late, it’s no secret that the construction industry is primed for change.
But change can be difficult for one of the oldest professions in human civilization, where superintendents and project managers traditionally unilaterally set the conditions of success, like schedule and budget. These traditional methods typically hinge on hierarchical and dictatorial, command-and-control–style processes, often limiting valuable input from key stakeholders without equitable distributions of risk. This environment exists throughout the project lifecycle from planning to handover.
Lean construction offers a better way. It’s a highly collaborative, people-centered process that involves all stakeholders in the production-planning stage, including those doing the work. When tradespeople are empowered to make decisions that affect the project schedule, bottlenecks are avoided, waste is reduced, and projects proceed more smoothly.
What Is Lean Construction?
The concept of lean began in the manufacturing sector with the Toyota corporation and was later adapted to the construction industry in the 1990s. Lean construction’s goal is to reduce surplus cost, material, time, and effort (identified as waste) on projects while increasing value, as defined by the client. Collaboration and accountability are key principles of lean construction, enabled by the availability of data that can detail every movement of people and materials across a construction site.
Lean construction targets eight types of waste for elimination:
1. Excess transport squanders time and carbon emissions.
2. Excess inventory wastes space and requires extra movement.
3. Excess motion refers to the circulation routes of people and things across a site.
4. Waiting is idle labor time.
5. Overprocessing is superfluous administrative or organizational processes.
6. Overproduction fuels excess inventory.
7. Product defects require redundant work.
8. Poor talent utilization fails to maximize productivity.
Lean gets its name from this relentless drive to reduce waste, sculpting and toning the construction process until it’s made of only what delivers value to the client while maintaining the health of those involved in delivering that value.
Lean construction is a broad philosophy rather than a discrete plan or toolset. It’s a series of principles to apply to a construction project, not a laundry list of tasks. Similar to integrated project delivery in the architecture world, lean construction requires all members of the building team (owners, representatives, contractors, subcontractors, specialty trades, and the boots-on-the-ground construction crew) to coordinate their actions from the outset of a project, taking on equal levels of accountability.
These early planning phases go a long way toward determining whether a lean construction project will succeed or fail. With lean, planning is no longer a siloed activity governed by a single project manager, based solely on their professional experience. All team members, from client to subcontractor, are expected to voice their expertise and actively shape a dynamic production schedule, ensuring that the full range of expertise on a jobsite is reflected.
In this environment, a sense of collaboration and respect means that individuals arranged horizontally across a team are responsible for holding each other accountable, instead of a vertical arrangement of project managers enforcing responsibility with carrots and sticks. Rather than enforcing discipline, a manager’s job is to facilitate the needs of the construction crew—to make sure they have the right labor, materials, milestones, and information to be successful. As Greg Howell, founder of the Lean Construction Institute with Glenn Ballard, puts it: “Assignments made by a foreman are promises to the following crew.”
Lean teams set only basic milestone deadlines toward the final project turnover. Teams weigh in on schedules at the outset of projects, then use a frequent, efficient meeting schedule to look ahead in granular increments, seeking certainty in the flow of logistics and labor before committing to deadlines. For instance, the start and end of interior finishings might be pegged to a certain date when the project begins, but a floor-by-floor schedule of paint and carpet installation might be agreed upon only weeks before the interiors deadline. Often, these more granular deadlines are set three to six weeks out and are monitored through check-ins focused on what’s planned and daily stand-up meetings on what’s actually completed.
The 6 Principles of Lean Construction
1. Identification of Value
Lean construction starts by asking the question, “What does the client want, and why do they want it?” An understanding of this guiding principle must be shared by the entire team.
2. Definition of the Value Stream
This entails defining which steps in the construction process create value and which do not. For instance, installation of cabinetry creates value for the client. Moving cabinetry into storage because it’s been delivered before drywall finishings does not. Lean construction teams can track how each step contributes to the final product with a Value Stream Map, which documents information flow, material flow, lead times, and process times.
3. Elimination of Waste
As listed earlier, wasteful practices decrease the value delivered to clients.
4. Work Process Flow
Lean construction projects are successful when teams commit to creating continuously iterative workflows that are regularly updated according to each team member’s expertise and judgment.
5. Pull Planning and Scheduling
Pull planning essentially plans the construction of a building in reverse, starting with the completion date and moving backward. With pull planning, new phases of construction begin based on downstream demand, which typically means subcontractors are setting the pace. This process is achieved only by working collaboratively to make sure all members of the team know the preceding steps before their part of the job can begin. Like traditional planning methods, pull planning lists what task needs to be completed, as well as what any individual team member needs to complete his or her work.
6. Continuous Improvement
Lean construction teams maximize their value and set the stage for future waste reductions by identifying ways to improve current and future projects. This means planning work, completing it, checking its quality and fidelity, and continuously adjusting actions—even midstream—to bring plan and action closer in line.
Benefits of Lean Construction
By setting a precedent for egalitarian, up-front coordination, lean construction gives team members a far greater understanding of how their work will affect the work of the next set of trades and professionals to work on the site. This reduces clashes, the need for rework, and construction sequence mishaps. A study of lean construction projects in the UK, US, and France found that approximately 50% of respondents saw reduced clashes, conflicts between tasks on-site, and reduced rework.
Overall, using lean has contributed to:
- An 84% gain in higher-quality construction
- A 74% reduction in project schedules
- A 77% increase in productivity
- An 80% improvement in customer satisfaction
Barriers to Adopting Lean Construction
The impediments to going lean tend to be cultural, social, and organizational—far more than they are technical or professional. Lean construction calls for some up-front training and education and absolutely requires top-to-bottom buy-in from all team members. It may also be necessary to attenuate suppliers to changes in how materials are ordered and processed. And because it requires so much collaboration and planning iteration, it’s particularly vulnerable to communication breakdowns, which tend to expand and spiral out from one team to the next.
Broadly, the biggest challenge to lean construction is making sure that disparate trades and professionals working on-site stay current on what their colleagues are doing. Once the professional silos that traditionally limit this kind of communication are broken down, it’s incumbent on team members to take their 360-degree understanding of the project out of the trailer, where plans are made and updated, and onto the jobsite, keeping everyone updated in a continual feedback loop.
Lean, BIM, and the Future
As a construction methodology, lean is complementary to any number of digital construction tools—including building information modeling (BIM), which, as a planning and communication tool, dovetails perfectly with lean construction’s strengths. BIM allows the lean construction’s up-front planning to be uploaded into easily comprehensible, visual models and workflow diagrams that are continuously updated and available to all. The iterative nature of lean is also accelerated by BIM, an environment where updates by all team members are immediate throughout the model and plan, driven by artificial intelligence and machine learning.
According to the Lean Construction Institute, projects that use lean are:
- Three times as likely to be ahead of schedule
- Two times as likely to be under budget.
That’s likely to fit any client’s definition of value—and any contractor’s definition of success.
This infographic was originally published in November 2020. Special thanks to architectural journalist Zach Mortice for the accompanying article.