Construction Estimating & Preconstruction Glossary

An addendum is a formal contractual modification issued during the competitive bidding phase prior to the formal bid opening. Addenda modify the original drawing sheets, project specifications, or contract terms, and must be explicitly acknowledged on contractor bid forms. Estimators must audit all addenda to update material takeoffs and price revisions before final proposal submission.

Alternates are specific scope variations priced independently on the contractor's bid form. An Additive Alternate increases the base scope and cost (e.g., adding an outdoor patio or upgrading mechanical equipment efficiency), while a Deductive Alternate reduces scope and cost (e.g., substituting luxury vinyl tile for terrazzo flooring). Owners utilize alternates to adjust total contract costs to match available capital funds.

A Request for Information (RFI) is the formal protocol used by contractors and estimators to seek clarification from the design team regarding conflicting drawing callouts, missing specification details, or constructability challenges. Pre-bid RFIs submitted during the tender phase often prompt the design team to issue official addenda to all bidding parties.

An allowance is an agreed-upon financial placeholder incorporated into a construction estimate when particular architectural finishes, lighting fixtures, or hardware have not been finalized by the owner or design team. Once final selections are made during construction, the actual invoice amount is reconciled against the allowance through an additive or deductive change order.

A detailed estimate (AACE Class 1 estimate) represents the highest level of preconstruction accuracy. Prepared from 100% completed architectural, structural, civil, and MEP construction drawings and specifications, a detailed estimate is built upon exhaustive digital quantity takeoffs, verified supplier quotes, localized labor productivity calculations, and itemized general conditions. Expected accuracy is typically within -3% to +5%.

Direct costs encompass all expenses incurred in the physical fabrication, delivery, and installation of permanent building components on a jobsite. Examples include concrete ready-mix, structural steel members, framing lumber, drywall sheets, electrical conduit, direct craft laborer wages, and equipment rented specifically for trade execution.

General Conditions (CSI MasterFormat Division 01) represent the jobsite operational infrastructure necessary to execute a project. Items include project superintendent salaries, field office trailers, temporary electric power, jobsite lighting, water supply, temporary fencing, trash dumpsters, routine cleanup, safety equipment, progress photography, and final building commissioning.

Indirect costs include home-office overhead expenses (corporate executive salaries, accounting, legal, insurance, marketing, office rent) and jobsite-wide indirect costs (permits, performance bonds, builder's risk insurance, temporary utilities). These costs are distributed across project line items as percentage markups or dedicated general requirement packages.

Overhead and Profit (O&P) is the final financial markup applied to a construction estimate. Overhead captures the cost of maintaining a contractor's permanent corporate business infrastructure (office rent, estimating software licenses, executive salaries), while Profit represents the net financial return earned by the business for assuming project contractual and operational risk.

A Bill of Quantities (BOQ) is a formal tender and contract document that breaks down an entire construction project into measurable, itemized components categorized by trade and CSI MasterFormat code. Each item features a detailed description, unit of measurement, net quantity, and unit rate. A BOQ ensures all bidding contractors price identical quantities, eliminating discrepancies.

A material takeoff is a procurement-oriented inventory that translates drawing dimensions into commercial order units. Unlike a pure quantity takeoff (which measures net geometric space), a material takeoff incorporates commercial packaging increments (e.g. 16-foot framing lumber lengths, 4x10 drywall sheets, 20-foot pipe joints) and cutting waste factors, providing a supplier-ready bill of materials.

Net in-place quantity represents the exact geometric dimension of finished building work according to contract plans. For example, a 100-foot-long by 10-foot-high wall represents exactly 1,000 square feet of net in-place drywall. Professional estimators always isolate net in-place quantities from material waste percentages, ensuring calculations remain transparent and verifiable.

A quantity takeoff is the core computational phase of preconstruction. Estimators utilize digital takeoff software to calibrate drawing scales, trace geometric boundaries, and calculate exact counts (doors, plumbing fixtures), lengths (piping, framing studs, conduit), areas (roofing squares, drywall, flooring), and volumes (concrete yardage, soil cut/fill) across every project sheet.

A waste factor is an intentional multiplier applied to net geometric quantities to ensure sufficient physical material arrives on the jobsite. Waste factors are calibrated to material characteristics, packaging increments, and architectural complexity. For example, straight-run ceramic tile receives an 8% to 10% waste factor, while complex roof hips and valleys receive 12% to 18% due to diagonal cuts.

Bid leveling is the disciplined preconstruction practice of standardizing competing trade subcontractor quotes to ensure an 'apples-to-apples' comparison. Because subcontractors frequently exclude certain tasks (e.g., cleanup, hoisting, sales tax, or firestopping), bid leveling identifies scope gaps, normalizes exclusions, and adjusts proposal numbers to determine the true lowest qualified bidder.

A conceptual estimate (classified by AACE International as a Class 5 or Class 4 estimate) is developed during the earliest stages of project feasibility when only rough sketches, square footage targets, or programmatic requirements are available. Estimators utilize historical parameter metrics (cost per square foot, cost per hospital bed, cost per apartment unit) combined with high design contingencies (15% to 25%) to test project viability.

Target Value Design is a collaborative, design-assist preconstruction methodology that inverts traditional practice. Instead of an architect designing a building and having an estimator price it, the owner's budget is treated as an unbreakable ceiling. Estimators work continuously alongside architects and engineers, providing instantaneous cost feedback on material choices and bay spacings to ensure the design never exceeds the target budget.

Value engineering is an analytical preconstruction review that analyzes the function of building components. By examining alternate materials, simplified structural framing details, standardized MEP equipment, or prefabricated modular assemblies, VE identifies significant capital cost savings and schedule accelerations while maintaining full architectural intent and building code compliance.

A contingency is an explicit line item included in a construction budget to account for unknown or unquantifiable conditions. Estimators distinguish between Design Contingency (reserves allocated for unengineered details during preconstruction), Estimating Contingency (allowances for pricing volatility and math tolerances), and Contractor Construction Contingency (funds for field coordination clashes and jobsite delays).

A scope gap occurs when an essential building component falls between trade jurisdiction boundaries and is excluded by all bidding subcontractors. Classic scope gaps include core drilling for mechanical pipes, concrete housekeeping pads for electrical gear, low-voltage control wiring for HVAC dampers, and perimeter firestopping between curtain walls and slab edges.

CSI MasterFormat is the undisputed industry standard for organizing construction specifications, drawings, cost estimates, and building data in the United States. Structured into 50 numerical divisions (e.g., Division 03 Concrete, Division 05 Metals, Division 09 Finishes, Division 22 Plumbing, Division 26 Electrical), MasterFormat provides a universal classification system that links project specifications directly to cost estimate line items.

A Work Breakdown Structure is the foundational organizational framework of an estimate. It divides a massive, complex building project into logical levels: Project -> Phase -> CSI Division -> Trade Package -> Specific Assembly -> Individual Cost Item. A standardized WBS ensures cost tracking remains consistent across estimating, purchasing, scheduling, and field accounting.

Labor burden is the composite percentage added to a worker's base hourly wage to capture all employer-paid payroll taxes and benefits. Components include Federal Insurance Contributions Act (FICA / Social Security and Medicare), Federal and State Unemployment Taxes (FUTA / SUTA), Workers' Compensation insurance, commercial general liability, health insurance, retirement contributions, and paid time off.

A unit cost is a composite pricing factor that combines the direct material cost, labor installation hours, equipment operating burdens, and small tool allowances required to install one standard unit of work. For example, a concrete slab unit rate might be $185 per cubic yard, capturing ready-mix supply, pump truck rental, placing crew labor, and finishing labor.

The Scope of Work defines the exact boundaries of what a contractor or subcontractor is contracted to perform, furnish, install, and warrant. In estimating, establishing a precise SOW ensures that trade scopes are completely allocated without overlapping jurisdictions or missing trade handoffs (e.g. clarifying whether the plumber or electrician connects the water heater power).