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Tuesday, October 4, 2016


Assemblies Cost Estimating

In my 'Looking Forward' blog post back in August, I tagged October as the month where I would be focusing on developing a construction budget for the Oakley home. I decided to attack this phase on a couple of different fronts. The first being on the contractor end, where I recently sent out drawings to my builder for pricing and to identify any potential construction issues I might be overlooking. The second being on my end, where using the Revit model, RS Means cost data software, and some modified spreadsheets from my thesis project, I am developing my own construction cost estimate (to better understand the process and pricing in more detail). I'll follow up on the contractor estimate in a future blog post, but below is a bit more about what all I am doing as it relates to this exercise.
Construction Cost Estimating is traditionally broken down into three different levels of detail ranging from square foot cost estimates (the least detailed), to assemblies cost estimates, to unit cost estimates (the most detailed). For my purposes as a real estate developer, I like to stick with the Assembly approach to estimating, which is a happy medium that calculates costs based on a combination of individual components that come together to make a system. A classic example of this being the drywall wall assembly, which groups together sheets of gypsum wall board, finishing tape, baseboard trim, and paint in a single cost per square foot line item that can be quantified and plugged into the assemblies cost estimate spreadsheet, rather than needing to account for each of these items individually (which is what the unit cost approach requires)
Below are a couple images that show the breakdown of the drywall cost assembly as described by RSMeans online and how Revit is able to do square foot takeoffs by selecting individual assemblies, which can also be scheduled.
Overall, assemblies costs are distributed across 9 different categories, which together combine to create a total hard cost construction budget, that will be plugged in as a line item in the master pro-forma spreadsheet, which will ultimately be used to finance the project. Below is a list of the 9 Assembly Cost Categories along with a sample breakdown of the Site Work category for additional reference, and be on the lookout for more blog entries on the entire estimating and financing process as it relates to the Oakley Home Project.
  • Assembly Cost Categories: (01) Site Work, (02) Foundation, (03) Framing, (04) Exterior Walls, (05) Roofing, (06) Interiors, (07) Specialties, (08) Mechanical, (09) Electrical