Automobile manufacturers have found such
dramatic quality and productivity results by using "lean
production" methods that the movement is sweeping through
manufacturers in all types of industries. Can builders apply
lean production to homebuilding? To explore the possibilities,
we must first understand the fundamentals of lean production.
More than a passing fad, lean production
is the culmination of a decade of development by automobile manufacturers
who have on average cut labor hours per vehicle by more than
half with one-third the defects. Over the last few years, other
industries, from toys to aircraft, have successfully adapted
lean production to their manufacturing operations with similar
results.
The core concept behind lean production
is to create a flow among value, creating work steps while eliminating
non-value steps. This has required changes to production processes
with some recurring themes:
- Broad skilled, multi-disciplined teams
replace functionally grouped specialists. In homebuilding, this
translates to a single, self-managed team comprised of craftsmen
with multiple skills for each phase of construction.
- Continuous workflow ensures steady production
rates that eliminate the chaos of fragmented stop-and-go production
processes. This means building a set number of houses per week
or month. Crew sizes are matched to the production rate so they
have continuous work.
- A focus on fast cycle times eliminates
non-value-adding activities. When non-value activities are removed
from the production process, cycle times drop until physical
limits are reached.
Transforming to lean production starts
by uncovering which steps create customer value commonly termed
the "value stream." This is accomplished by flow charting
each step of the production process, then defining which steps
add customer value. In his book "Lean Thinking," James
Womack identifies three types of work steps according to their
contribution to customer value:
- Some steps unmistakably create customer
value, such as nailing studs together or connecting wires to
an electrical outlet. Lean production aims to eliminate all steps
except for these.
- Other steps create no value but are unavoidable
with current technologies and processes, such as code inspections,
scheduling, or setting up concrete forms for foundations.
- Additional steps create no value and are
immediately avoidable, such as duplication of effort or idle
time.
Create a vision of a new production system
with only value-creating steps organized into a continuous flow.
Unconventional thinking is necessary. For motivation, think of
the enormous cost and time savings you can achieve if all but
value-creating steps are eliminated.
It is easy to eliminate obviously wasteful
steps immediately. The hard part is the new thinking required
to remove seemingly "unavoidable" steps that do not
add value. Often, this involves eliminating reasons for the step
in the first place. For instance, daily production scheduling
would not be necessary if a steady production rate and continuous
flows were in place.
How much potential lean construction has
for the traditional homebuilding process remains to be seen.