A Way to Concurrent Design and Construction
|Corresponding Author: Kiiras, Juhani|
|Author(s): Kiiras, J.|
|Organisation(s): Construction Economics and Management, Helsinki University of Technology (Finland)|
|The suggested paper is related to our completed research program, titled
”New national procurement methods for building in Finland” which was funded,
as a part of the national PROBUILD Program, by Technology Development Centre
in Finland (TEKES).
In this paper, I look at scheduling principles of design and construction work. I will show that by breaking location down to small lots or zones and completing them through short througput times, before stating a new one, we enable the effective adoption of concurrent design and construction (CDC), i.e. in order to ensure better quality, to reject design changes, and to avoid quality faults.
The principles (compare with the attached figure) of CDC are as follows:
Rough overlapping means hard load on designers. Control and monitoring is difficult. This requires high experience from the project manager, and is very risky. We have many control points at the specified moments. Possibilities for quality faults are many.
We can ensure effective overlapping by using construction management method, trade contracts, and design for trades. Design time can be longer or shorter, but possibilities for quality faults do not increase. Scheduling of design and control of actual works is easier than in rough overlapping.
Short througput time of locations is, in principle, similar to just-in-time (JIT) ideas in manufacturing industry. The works of each lot or zone are completed before starting a new one. Thus, design changes and faults can be corrected before opening the next lot. There is less unfinished work and constant production rate. Lot-by-lot execution requires only a few (or one) control points at the same time. Of course, delivery logistics changes to that of just-in-time method, collecting and delivering, at the same time, all the materials needed for the lot(s) under execution.
In Finland, we have used short throughput time and location breakdown to small lots or zones in many refurbishment projects and in construction of apartment infills ”on demand”. In renovation projects, the results were good: shorter project durations but longer design and construction times, better productivity, and better quality at the same time.
When using very short throughput construction of apartment infills, after the deals with occupants (on demand), we got lower inventory rate and good quality, at the same time when the customers could choose among the alternative customized interior solutions or they were allowed to design their own solutions.