Cost Estimation Overview
Architects are not expected to produce contractor-grade estimates, but the ARE tests your understanding of estimating methods, when to apply them, and how to manage a project budget through each phase of design.
Estimating Methods by Phase
| Method | Phase | Accuracy |
|---|---|---|
| Square foot / unit cost | Schematic Design | Low (+/-15-20%) |
| Assemblies (systems) estimate | Design Development | Moderate (+/-10-15%) |
| Detailed / unit price estimate | Construction Documents | High (+/-5-10%) |
| Contractor's bid or GMP | Bidding/Negotiation | Highest |
As design progresses, estimates move from broad parametric comparisons to line-item takeoffs based on actual quantities and unit prices.
Square Foot Estimating
Uses historical cost-per-square-foot data from similar building types, adjusted for location (via a cost index), size, quality, and market conditions. Useful early when few details exist.
Assemblies Estimating
Costs are organized by building systems (e.g., foundations, exterior walls, roofing) rather than individual trades, aligning with UniFormat classification. This method is common during Design Development when systems are defined but not fully detailed.
Unit Price / Detailed Estimating
Based on quantity takeoffs from construction documents multiplied by unit costs (labor + material + equipment), organized by MasterFormat divisions. This is the most accurate but requires complete documentation.
Value Engineering
Value engineering (VE) is a systematic process to improve value - the ratio of function to cost - without sacrificing performance. VE typically occurs when an estimate exceeds budget and involves:
- Identifying essential functions vs. cost drivers
- Generating alternatives that preserve function at lower cost
- Evaluating trade-offs in first cost vs. operating cost
Note: VE is not simply "cutting scope" - it should maintain or enhance value, and architects should document impacts to quality, schedule, and life-cycle performance.
Life-Cycle Cost Analysis (LCCA)
LCCA evaluates the total cost of ownership over a building's useful life, including:
- Initial (first) costs: Design, construction, financing
- Operating costs: Energy, water, maintenance
- Replacement costs: For components with shorter service lives than the building
- Residual value: Salvage or disposal value at end of study period
LCCA often uses net present value (NPV) to compare alternatives on equal footing, discounting future costs to present-day dollars. A higher first-cost system (e.g., high-efficiency HVAC) may have a lower life-cycle cost due to energy savings.
Budget Management
Architects reconcile design against budget at each milestone, tracking a running estimate against the owner's project budget. Contingencies (design contingency, decreasing as documents progress, and construction contingency for unforeseen conditions) are essential tools for managing risk. Budget overruns are typically addressed through VE, scope reduction, or owner-approved budget increases - never silently absorbed.
Exam Tips
- Match the estimating method to the design phase - this is a frequently tested pairing.
- Understand that LCCA favors long-term efficiency even at higher first cost.
- Cost estimation connects directly to Project Delivery Methods (e.g., GMP contracts) and Contract Types.
- Schedule impacts of cost decisions are covered in Scheduling Techniques.
Master cost estimating concepts for PcM and PjM with targeted practice - start free on AREprep.