by TIM KELLY, Assemble Systems
This article was originally published to the Assemble Systems blog on March 22, 2016.
Due to the industry shift towards integrated project teams, a lot of contractors are getting involved earlier in the design phase. This means that leveraging design models for construction purposes is increasing in importance allowing contractors to use the models efficiently. When I first started in a BIM role, we would attempt to utilize the designer’s model for preconstruction, but I felt very disconnected from the design process and a majority of my time was spent remodeling or conditioning the model for our workflows. While we all understood the benefits the model provides, this process was rather time consuming. This was a rather tedious exercise when new model iterations were shared by the architect.
In the past few years, I have seen designers and contractors move towards a more collaborative process, concentrating on reducing rework and creating a more seamless workflow. The earlier the contractor can inform the designer about the intended use of the model helps the designer make small changes in how they model which can have tremendous impact.
For example, when designing a multi-story building, it might be easier to place a single column that extends from the first floor to the tenth floor, but it is never going to be built that way. Contractors are not going to pour concrete for objects that stretch the height of the building, so eventually the model needs to be adjusted and re-configured for proper constructability, which impacts the model usage. Taking a small extra step of placing the column by level (you can even place one on the first floor then copy it up to each floor in a single step) earlier as the design develops will allow for better analysis of budget, logistics, phasing and schedule consideration during the design phase.
Below are three essential tips to designing a constructible model:
- Consider the Work Breakdown. One of the first processes a contractor goes through is how to approach the project. Communicating this to the designer earlier in the design process may allow for better model development. The model can then be quickly consumed to understand material quantities per phase, potential project cash flow requirements, etc.
- Consider the life of the model. Improving model integrity increases the life of the model beyond creating 2D documents. The attention to detail in design allows for a model that is easily conditioned during construction with as-built information, and can be handed over to the owner for facilities management upon project completion.
- Improve communications. Often, the lack of communication between design and construction teams may lead to major problems throughout the project and can be the cause of damaging delays. Expand communication between the design and construction team early to avoid potential budget overruns, schedule impacts, or redesign and ensure the project is completed with the proper scope, on-time, and within budget. This thought is well captured by the famous MacLeamy Curve, the further you are through the design process, the higher the cost of design change. With the right BIM management tools in place, the project stakeholders can work collaboratively earlier in the process and implement an integrated approach to project design and delivery to control the costs.
At the end of the day, modeling for constructability is more of a practice of common sense around the design, pre-construction, and construction process. Building strong designs with construction in mind while opening clear communications between teams allows for better scope, budget, and time management.