SD, DD, CD, IFP, IFC: Project Phases

Project phases are often reduced to a string of abbreviations, but each phase represents a different level of information maturity, coordination, and risk. Confusion usually arises when documents are treated as more, or less, complete than they actually are. One way to understand this progression is through Level of Development (LOD), a concept that describes how reliable and decision-ready information is at a given point in the project.

The CSI Project Delivery Practice Guide frames project delivery around progressive information development, emphasizing how information is created, relied upon, and transferred as a project moves from concept to construction and occupancy. From this perspective, clarity about what information exists, how reliable it is, and how it may be used is more important than the issuance label alone. LOD provides a useful lens for aligning those expectations across the design and construction team.

PD — Pre-Design (Typically LOD 000–100)

Pre-Design (PD) occurs before formal design phases begin and focuses on defining the problem to be solved, rather than the solution itself. For MEP systems, PD may include existing conditions assessment, utility availability review, preliminary load benchmarking, infrastructure constraints, and high-level system feasibility studies. The goal is not to select systems, but to establish realistic boundaries for what is possible.

At this stage, MEP information typically aligns with LOD 000 to early LOD 100, meaning information is largely narrative, performance-based, or diagrammatic rather than geometric. Data may include ranges, targets, or precedents rather than calculated outcomes. From a PDPG perspective, PD information supports decision framing, not design development or coordination.

During PD, MEP teams should work closely with Owners to clarify project goals, operational priorities, budget constraints, schedule drivers, and risk tolerance. This is also the appropriate phase to identify site or utility limitations, regulatory hurdles, and systems that may drive early cost or space decisions. Assumptions formed during PD, particularly around infrastructure capacity, energy strategy, and resiliency, often persist throughout the project, making it critical that they are documented, tested, and aligned before advancing into Schematic Design.

SD — Schematic Design (Typically LOD 100–200)

Schematic Design (SD) establishes overall intent. For MEP systems, this includes preliminary system selection, conceptual routing strategies, early load assumptions, and identification of major equipment and space needs. Decisions at this stage are directional and exploratory, intended to test feasibility rather than resolve detail.

At this point, MEP information generally aligns with LOD 100 to early LOD 200, meaning systems are represented conceptually with approximate capacities and relationships rather than fixed sizes or locations. From a PDPG standpoint, SD information supports alignment and decision-making, not pricing precision or constructability resolution. MEP coordination at SD is most effective when Owner priorities and constraints are clearly understood before assumptions quietly solidify into decisions. Key assumptions, such as loads, space allowances, and system types, should be documented explicitly so they are visible to the entire design team and not silently carried forward.

DD — Design Development (Typically LOD 300)

Design Development (DD) is where MEP systems become defined. Equipment capacities are refined, distribution paths are established, and coordination with architectural and structural systems intensifies. Many cost- and space-driving decisions are effectively locked during DD, even if drawings still appear incomplete.

Within the PDPG framework, DD represents decision-confirming information, typically aligning with LOD 300. At this level, systems are defined with sufficient accuracy to support coordination, scope confirmation, and meaningful pricing, though not full fabrication detail. Owners and cost consultants increasingly rely on this information to validate budgets and schedules. During DD, MEP firms should confirm which assumptions are now fixed decisions and which remain flexible, while coordination focuses on shaft sizing, ceiling zones, equipment access, and spatial conflicts. Pricing exercises during DD should reflect this level of development, not assume construction-level certainty.

CD — Construction Documents (Typically LOD 350–400)

Construction Documents (CD) translate coordinated design decisions into buildable instructions. MEP drawings and specifications at this stage are detailed, dimensioned, and suitable for permitting and construction.

The PDPG treats CD information as instructional; it is intended to be relied upon by others to execute the work. From an LOD standpoint, CDs typically align with LOD 350 to LOD 400, where system interfaces are defined, coordination is resolved, and information is reliable for construction interpretation, even if final fabrication details are still deferred. At this phase, MEP teams should confirm that design intent is fully documented, delegated design responsibilities are clearly defined, and permitting strategy aligns with AHJ requirements. Internal consistency across drawings, schedules, and specifications becomes critical, as the information is now relied upon contractually.

BP — Building Permit (LOD Similar to CD, but Purpose-Limited)

Building Permit (BP) documents represent a subset or refinement of the construction documents prepared specifically to support Authority Having Jurisdiction review and permit issuance. For MEP systems, this may include jurisdiction-specific calculations, code narratives, or revised layouts developed in response to plan review criteria.

While BP sets often reflect LOD levels similar to Construction Documents, their purpose is limited to regulatory approval rather than construction reliance. Best practice is to clearly identify BP sets by intent and to confirm exactly what the AHJ requires for approval. MEP firms should also communicate whether permit issuance authorizes construction or whether additional revisions are anticipated prior to IFC, as permit approval does not automatically imply construction readiness.

BN — Bidding / Negotiation (LOD Varies by Use)

Bidding and Negotiation (BN) is the phase where MEP design information is actively relied upon for pricing, scope definition, and procurement. Contractor questions, substitutions, and value engineering proposals are common, and the quality of earlier coordination becomes visible.

From a PDPG perspective, BN is where information reliance increases sharply, even if design responsibility has not shifted. During this phase, MEP information may span LOD 300 to 400, depending on how close the documents are to IFC. MEP engineers should ensure that pricing questions and proposed alternates are evaluated against actual design intent, not incomplete assumptions. Clear differentiation between acceptable alternates and scope changes helps Owners understand cost impacts without eroding performance, compliance, or long-term system reliability.

CA — Construction Administration (LOD 400–500 via Submittals)

Construction Administration (CA) extends the design process into the field through submittal review, RFIs, site observations, and interpretation of the contract documents.

The PDPG emphasizes that CA is not a passive phase, it is where design intent is validated against constructed reality. During CA, responsibility for developing LOD 400–500 information typically shifts to contractors and fabricators through shop drawings and submittals. The MEP engineer’s role is to review this information for conformance with the contract documents and design intent, not to recreate fabrication-level design. This phase ultimately reveals the effectiveness of coordination and decision-making from earlier stages.

Issuance Designations: IFP, GMP, and IFC

Issuance labels add another layer of meaning, but they are industry conventions rather than formally standardized terms.

IFP (Issued for Pricing) typically indicates that documents are sufficiently developed, often around LOD 300 or early LOD 350, to support cost estimating, competitive pricing, or Guaranteed Maximum Price (GMP) development, but are not yet final or approved for construction. In GMP delivery models, IFP sets are commonly used to establish pricing based on the best available information at that point in the design process.

Because IFP documents are not fully resolved, GMPs developed from these sets inherently include assumptions, allowances, contingencies, and clarifications to account for remaining design development and coordination risk. From an MEP perspective, this makes it critical that design intent, system performance requirements, and known unknowns are clearly communicated so pricing reflects the true scope rather than optimistic interpretation.

IFC (Issued for Construction) confirms that documents are complete, coordinated, and generally aligned with at least LOD 400, meaning they may be relied upon contractually in the field. Unlike IFP sets, IFC documents are intended to remove ambiguity rather than manage it, shifting risk away from assumptions and toward execution.

The CSI Project Delivery Practice Guide reinforces that documents should be used only for their intended purpose, regardless of how they are stamped. Treating an IFP or GMP set as construction-ready without acknowledging its underlying assumptions is a common source of disputes, change orders, and schedule impacts.

The Takeaway

Each project phase represents a different level of information maturity, and LOD provides a common language for understanding how much confidence can be placed in that information. When phase, LOD, and issuance intent are aligned, risk is reduced and decision-making improves.

Good project delivery depends on asking the right questions, making the right decisions, and relying on the right documents at the right time. At Aethera Engineers, we emphasize phase clarity, LOD awareness, and proactive coordination with Owners and the full design team so MEP systems move from concept to construction with fewer surprises and better outcomes.