Estimating Using Assemblies - Another Wonderful Tool in the Architects/Estimators Arsenal

Be warned, this is a bit dry, but it’s something that all people composing cost estimates should read.

We were recently hired to build cost assemblies - which is essentially a group of line items bundled together for a specific task. For example, the assembly can be removing and replacing flooring - so we have cost line items such as demo existing flooring, labor to haul the demolished product, costs to dispose of the waste and labor/materials to install the new flooring which could include waterproofing, floor leveling compound and the new flooring materials. On top of that there also may be some sort of sealant and some protection board to cover the newly installed floor while other construction activities are happening. What I’m getting at is this: That for one simple task - “replace flooring” - there can be multiple cost line items to make up that task.

When we teach, we always implore our students to estimate from both a big picture perspective as well as from an “in the trenches” perspective. This thinking from all sides allows accountability for all tasks.

When I was starting out, I was green and thought replace flooring was simply demo of the existing and installing new. Over time I learned that the devil is indeed in the details, and without exploring all scenarios, without reviewing all the notes/details and without thinking of all the tasks, I was leaving a lot on the table. Thankfully I’ve learned a few things along the way - and in estimating various phases of a project, I realized that most all estimating is basically creating assemblies of tasks.

Assembly estimating is a useful tool, especially for early conceptual estimates. I often encourage design professionals to use assemblies - they are typically more accurate than square foot estimating. RS Means publishes a great assembly cost estimating book. Estimators and engineers have taken the time to compose a detailed list of all items for each task, and they roll up into a final simple cost - which can be expressed in square footage or square yards or various other measurements.

Using assemblies when estimating, combined with adjustments for locality, current market conditions and current material costs allow everyone in the construction chain to estimate more accurately than using historical costs alone.

So, what am I getting at? There are multiple tools to use and this is just another one. If you are responsible for creating assemblies, be sure and vet out all the tasks, there are often more than those that first come to mind. Talk to the experts, the contractors who do the work daily, they are often the best source to find out what really goes into a task.

Assembly estimating can be accurate once you adjust for what I mention above and it can save so much time. So next time you are tempted to rely on historical costs to throw some square foot numbers together, reach for assembly cost data - it’s already built, easy to adjust and provides a pretty accurate idea of job costs. We are all trying to save time and stay accurate, so why not use a tool that essentially does the job for us?