An Assemblies or Systems Estimate is a type of estimate typically used on larger commercial projects where a particular assembly or system repeatedly appears in project. They are usually preformed while a project is still in the design stage and are generally considered to provide accuracy in the ± 10-15% range. They don’t generally need finished design drawing and in fact they are often done while the the design is “approaching the 25-30% complete stage“. An Assemblies or Systems estimate is best used as a budgeting tool.
They are arguably a type of Parametric Estimate.
Assembly and Systems Estimates are intermediate level estimates performed when design drawings are between 10% and 75% complete. Assemblies or systems group the work of several trades or disciplines and/or work items into a single unit for estimating purposes. For example, a foundation usually requires excavation, formwork, reinforcing, concrete—including placement and finish—and backfill. An Assembly and Systems estimate prices all of these elements together by applying values available in assemblies cost data guides. These guides are based on historical databases, typically organized in MasterFormat™. Estimates made with this method can be expected to be within 10% accuracy. — Estimating | WBDG Whole Building Design Guide
…An Assemblies Estimate is usually prepared when the architect completes the design development plans.
The Systems method is a logical, sequential approach which reflects how a building is constructed. Seven “UNIFORMAT II” major groups organize building construction into major components that can be used in Assemblies Estimates. These UNIFORMAT II divisions are listed below:
Assemblies Major Groups:
A – Substructure B – Shell
C – Interiors
D – Services
E – Equipment & Furnishings
F – Special Construction & Demolition G – Building Sitework
Each major group is further broken down into systems. Each of these systems incorporates several different items into an assemblage that is commonly used in building construction. — Means Unit Price Estimating Methods -by Phillip R. Waier (Editor) RSMeans/Reed Construction Data