Recapping the previous post, we explored the misconceptions surrounding Lean and its applicability to offsite construction. Unlike the mass production of Henry Ford, Lean was created specifically to manage lower volumes and higher variability. We also discussed how the ideal Lean system can be adapted in the beginning, with continuous improvement to move towards that ideal.
Many definitions of Lean exist, but few provide context for our industry, it’s not surprising that these misconceptions exist and the lack of clarity can lead to confusion. That’s why I’m passionate about getting back to the basics and digging into what makes lean work. This series aims to set down some key ideas to follow and give them context within our industry. These key ideas are intended to help start the journey into lean principles and build a strong foundation, both in practice and company culture.
In their book ‘Lean Thinking’ Womack and Jones[1] introduce the ideas that form the core of lean along with guidance through the process, ‘Lean for Dummies’[2] defines this as a 4 step process.
- Scrutinize the value stream
- Keep it Flowing
- Pulling through the system
- Striving for Perfection
Earlier this year Autodesk released their guide[3] with 5 steps (they separate ‘identify value’ from the ‘value stream mapping’ (VSM) in step 1 above). The Autodesk construction cloud has a number of good resources on the subject. I may not totally agree with everything they say but it’s worth reviewing.
However, no matter how you approach it, the first step is simply to understand what you need to do to deliver the customer what they want. This value is defined by the customer and what they are willing to pay for as defined by Womack and Jones[1].
‘A specific product (a good or a service, and often both at once) which meets the customer’s needs as a specific price at a specific time’
The value stream is the process that answers the question, the customer wants something how do you get it there? Or in simple terms what activities are needed to take the raw parts and convert them into the final product. The terms value adding (VA) and non-value adding (NVA) activities are used to describe these activities, defined by Sayer and Williams[2] value added activities must meet three criteria
- The customer must be willing to pay for it
- The activity must transition the product or service in some way
- The activity must be done correctly the first time.
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| Install of Modules on site, VA or NVA? |
Value stream mapping is the documentation of this process, when discussing how important considering the whole system is I briefly introduced VSM in part 2 of ‘Exploring the lean house’. The common approach is detailed and in-depth. Typically, at the beginning of a lean transformation this may be a section of the manufacturing process know as the model line. This gives a demonstration of the power of Lean, and the success of the model line then garners enthusiasm and commitment from the wider company. Those involved and trained on the model line will take their learning and expand lean practices through the company. This typical transformation is commonly applied to an established company in an established industry.
The construction sector however is relatively new to industrialisation with more in common with Industry 1.0 than modern manufacturing. So, the question is how do we get started? Like the situations in my last post there are benefits to bending the standard approach to get started and then use continuous improvement to move towards the ideal.
“Let’s carry out a detailed value stream map to identify the low hanging fruit”
This is a genuine quote from a former co-worker, it’s clearly contradictory but helps illustrate the issue with detailed VSM projects early on. By definition ‘low hanging fruit’ should be obvious so spending time detailing out a VSM to find it is unnecessary. Then, solving those issues will likely have a big impact on the VSM details, making all the studies, time data and detailed evaluations obsolete. Much better would be to sketch out a high level map to help prioritise the issues, and as you work on each problem record your results and improvements to increase the detail you hold in the VSM.
This approach offers several advantages. Firstly, you can quickly sketch the entire system at a high level. This allows you to prioritise issues and focus on the areas that will have the most significant impact on project delivery. By asking the question does the solution increase 'throughput' while simultaneously decreasing 'inventory' and 'operational expense'? Starting with challenges closest to customer handover helps ensure earlier solutions have a real impact on overall efficiency, preventing bottlenecks and unnecessary inventory. Then, as you tackle each problem, record your results and improvements, adding valuable detail to the VSM while also getting the benefits of the improvements.
Adopting this approach at a high level in the business will also promote a good culture, when making critical decisions on project timescales it’s good practice to ask the questions around the three metrics and if this choice deliver to our customer sooner? It’ll help cement a problem solving culture, one that won’t self-sabotage by pushing inventory into the system just to be seen to be doing something.
Lastly there is another layer beyond the processes that need to be completed, across the top of the VSM information flow is recorded, where it’s produced and where it’s used. By understanding this and working from the customer end, delays and problems can be avoided. Particularly around final sign offs from warranty providers, building control and the local fire brigade. When you know what they will want to see you can make sure you are collecting that info and evidence in advance without the need for potentially destructive inspections.
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| 80 Mod Project rough sketch VSM |
If we look at this on an example project, an 80 model block of flats, in a factory with a solid design that’s understood and known it’s not too difficult to get to an output of 3 modules a day. With a 6 day lead time for the first module on the line to leave the building those 80 modules can be built with a 2 week pre-flight and 6 weeks of main production. Typically that 2 weeks prep time overlaps with the end of the previous main production run so having a project finished every 6 weeks isn't out of the question.
Then a typical install currently can manage 5/6 modules a day for a floor a week and then the roof (5 weeks), this is followed by finishing work both internal and external, which can easily take 12 weeks or more and then snagging for another 4 weeks and a couple of weeks for final handover. Now this is some very rough timings and possibly quite generous to many with the current industry performance. But that site time of around 21 weeks means that to consistently use the factory output at least 4 active building sites need to be running at any one time.
All of that means a large stock of unfinished inventory (320-400 modules), lots of concurrent operational expense and poor throughput. Using the VSM approach it very clearly highlights that we need to focus our efforts on the site side of volumetric and MMC in general. This whole exercise took about 20 minutes and it very clearly illustrates an obvious risk, yet companies setting up factories have spent jaw dropping amounts of money on factories and factory infrastructure and clearly haven't been able to grasp this concept. From this simple VSM we can see that investing in a factory that produces 6 modules a day by automating will have a small impact of at best 3 weeks to the total lead time while driving up inventory as now 8 sites would need to be active, whereas targeting the non value add of Snagging has the potential to eliminate 4 weeks, reducing inventory while costing orders of magnitude less to achieve. And none of this even accounts for the most un predictable and very costly risk to the site side, our delightful British weather.
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| Snow falls on site |
In my next post I'm going to explore how the lean company can approach these risk and problems utilising this knowledge to tackle the low hanging fruit. How the senior team can set out a companies goals and strategies with Hoshin Kanri, targeting the model line to make the biggest bang and even look at a fantastic solution and foundation for revolutionising the site process.
And if you find these articles interesting and would like to discuss more, please feel free to message me on LinkedIn.
[1] Womack J.P., Jones D.T., (2007) Lean Thinking, Simon and Schuster.
[2] Sayer N., Williams B., (2012), Lean for Dummies 2nd edition, John Wiley & Sons, Inc.
[3] Autodesk, (2023) Discover Lean Construction: Why and how your construction teams should go Lean, Autodesk construction cloud
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