Which brings us to our next topic, Cost and Material Estimating. There are two essential aspects to this process, quantification of elements needed to construct the project and the total cost associated with the construction of those elements. This requires much more than just pricing out the purchase and labor cost of these elements. It requires understanding the conditions in which the elements are installed, long and short distance transportation costs, storage and staging, modularization, and this list goes much farther than my knowledge of this area. Truth be told, this is probably the area I know the least about. Not that I don’t understand or want to learn more, I just haven’t had the opportunity to be fully engaged in this part of the process. However, I do know about quantification side of it and that’s the side that Revit knows best too. That is what we’re going to focus on, how our ability to quantify project elements through BIM frees up the people that do know detailed cost estimating from doing time consuming takeoffs. As a result they will be able to focus on quantifying the intangibles like weather proofing work areas because the shell is being built during the winter months, or considering continuous transportation of materials from a staging area that is on the other side of campus.
If you haven’t already guessed where I’m going with this, I’m going to tell you that it’s just another area where Integrated Project Delivery and BIM exceeds over traditional project structures and of course over 2D construction documents. Although early pre-design estimates would still tend to be done in the traditional sense and require manual takeoffs from P&IDs and other scope summary documents, IPD and Revit would allow the estimates to be continually refined and validated throughout the design process and into construction.
Identifying Related Scope
Jumping back to line numbers and scope specific parameters to identify relationships between elements, let’s dig a little deeper into how this data can help quantify cost estimates throughout a project and provide continuous visibility into a project’s progress. We talked about line numbers and how they are great for managing piping design, but let’s stick with scope based parameter sets so that we can look at the project holistically. By utilizing scope parameters you will enable your team to break the project in manageable pieces. As I said early, it’s up to your project team to decide what the parameter set is based on, and that it is essential to establish the parameter at the very beginning of your project. For example, if you decide to break the project out by scope or work area, you might have a shared parameter called G_WorkArea, apply it to all model elements, and populate it with WA01, WA02, WA03, etc… depending on which work area of the building the work is being executed in. The format of the parameter content is crucial though in that if I set my filters to look for WA01 and elements are assigned to WA1, without a zero, those elements will get missed. It’s a good idea to have your discipline leads or BIM champions include this back check in their QA process.
By providing this level of granularity, it will open the door for VE options as well. You will be able to look at the project cost as a whole and then analyze each scope or scope area, apply cost saving ideas and then see the quantities go down in real time. You will also be able to see cost implications of modularization in real time. If I add a series of valves to allow a new system to be installed on modularized skids, I can see the cost impacts of that and determine if that method will save money or if the enabling required for modularization ends up adding cost.
Let’s look at another example. As I’ve probably already said, I live in the retrofit world. Although I work on the occasional green field project, the vast majority of my career experience is retrofit work, and I like it the way. I love the challenge of retrofitting entire new system into an already cramped facility without being able to shut down any of the existing systems. Using a parameter set based on specific scopes makes it easy for us to not only quantify and estimate, but also track progress, filter views, perform clash detection, and pretty much anything else you can think of. A typical project for me might consist of a boiler installation, an MAH installation, a handful of compressors, filters, heat exchangers, and plethora of distributions. So for us, being able to apply a unique number to each of those specific scopes allows us to isolate that scope and all disciplines involved from the other scopes. For this example the shared parameter might be G_SOW, be applied to all model elements, and be populated with 1001, 1002, 1004, etc… based on the scope of work number that was designated to the scope during pre-design. Again, format is paramount, and I suggest starting with an alpha or non-zero number or to avoid format confusion and third party applications like excel removing the leading zero.
Material Takeoffs
Once you have your methodology for identifying and organizing scopes, you can then begin the ongoing quantification process through Revit schedules. My advice is to establish the format of these schedules before deploying project files. That way all the required fields can be coordinated with your construction counterparts and any new required shared parameter can be created and deployed as well. If the information is available early enough, you can push those parameters to the families before deployment rather than relying on project parameters, but that is up to you and not always a luxury we are given.
When creating your quantification schedules, you will have some decisions to make. For starters, although a multi-category schedule is a nice catch all schedule, it lacks a lot of category specific available fields since it will only make those fields available that are common to all elements. In regards to piping, you would lose size, length, system, and any other fields that are specific to pipe. So the multi-category schedule is probably not the best choice for this task. However, it does make a great choice for back checking things like your scope of work parameters to ensure that all elements that need them, have them. That was one of my jobs during the pilot project. At the end of each day, I would pull up the back check schedule and ensure all elements were populated. It was a tedious but necessary task. Another option, is a material takeoff schedule, but for us MEP folks it’s not the right fit either. The bottom line is that a set of category specific schedules is the best way to go in my experience. That is why it is best to set these up prior to deployment. You don’t want to go back after the project has started and push 20 different schedules out to 20 different models. The category specific schedules, if formatted uniformly, can easily be combined on sheets or once export to excel.
SCHEDULES MERGED ON SHEET
SCHEDULES MERGED IN EXCEL
Once the schedules are set up and populated, it’s easy to provide construction estimators with report outs periodically throughout the project. This can be done on a weekly basis to monitor progress and evaluate high level project costs, but for detailed material takeoffs and cost estimates you might want to limit to only at a few key review milestones in the design process, 60%, 90% and IFC. The 30% milestone for us will typically be where P&IDs are finalized, equipment is located and maybe schematic or concept routing is modeled. 30% review probably won’t have enough model content to have estimating value but could be included for progress tracking methods. The schedules can then be exported a number of ways depending on your capabilities and what your construction estimators requirements are. The most straight forward approach, and my personal preference, is to simply export to excel. This can be done by using Revit’s native schedule export function, or through an add-in like BimLink. Another option is to use ODBC connection to export to a number of estimating programs. The other option, if you are lucky enough to have a Revit guru on your payroll, is to tailor build an export tool-set through the Revit API. Either way, the beauty is that Revit is doing all of the quantification work which will significantly reduce the potential for error, time consuming manual takeoffs, and the cost involved with the estimating process.
Project Metrics
The other side of estimating is not necessarily tied to construction cost, but rather estimating cost relationship between projects to improve design fee and labor estimates for future projects. Over time we can start to evaluate trends and better recognize cost saving opportunities. This is a powerful tool when selling IPD to a client because at the end of the day, they are the ones who have to buy into it and the advantages of a IPD approach are not always visible on the price tag. So having these metrics will help demonstrate that yes, design fees might be much higher, maybe double that of the traditional approach, but that cost will be offset by savings in construction and time to market due to schedule acceleration opportunities.
Revit makes evaluating these metrics as easy as quantifying model elements for construction estimating. Linear feet of pipe, duct, cable tray, etc… can be compared to design labor hours billed throughout the project. Schedules can be exported and analyzed through excel pivot tables, or data analysis programs like tableau. I used the example below to evaluate how many linear feet of each pipe spec were modelled in a recent project. This allowed us to evaluate and prioritize improvements for upcoming projects.
A word of caution when establishing these metrics though, linear feet of pipe, tonnage of steel, and square footage of walls when compared to man hours are all useless numbers by themselves. They need to be compared to other metric sets form previous and similar projects to have value. There is also a complexity factor that needs to be considered. For example, I can route 200 feet of pipe in under a minute, so long as the pipe is straight and has no valves. Conversely, it may take me two days to route 50 feet of pipe if the routing is complex, weaves through an existing facility, and there are control stations at either end. That is why it is a good idea to also consider quantifying fittings and accessories as a complexity multiplier for pipe or duct. For structural or architectural, a complexity factor might be based on the number of details issued or detail components used. Either way these numbers will grow in value over time, but will require time for them to have value, so start quantifying now.