B101 Basic vs Supplemental vs Additional Services

How AIA Document B101 organizes architect services into three distinct categories: basic services performed across five design phases, supplemental services identified at contract execution, and additional services that arise during the project. Covers fee implications, scope management, and how misclassifying services creates risk for architects.

ARE · Practice Management

Overview

Every owner-architect relationship starts with a question: what exactly is the architect responsible for? AIA Document B101-2017 answers that question by sorting all possible architect services into three buckets. Each one carries different contractual weight, different fee structures, and different risk profiles.

Basic services are the core of the agreement. They cover the five standard phases of project delivery: schematic design, design development, construction documents, procurement, and construction. These services are baked into the base fee, and the architect is obligated to perform them once the agreement is signed.

Supplemental services sit in a gray zone. They aren't part of the five-phase basic package, but the owner and architect agree at the time of contract execution that the architect will provide them. Think programming, site evaluation, LEED certification support, or furniture design. They're anticipated from the start and priced accordingly.

Additional services are the wildcard. These arise after the agreement is executed, triggered by unforeseen conditions, owner requests, or code changes mid-project. The architect isn't obligated to perform them without written authorization and separate compensation.

Understanding these three categories is critical for the ARE because scope creep, fee disputes, and professional liability exposure all trace back to how services get classified.

Essential

AIA Document B101-2017 is the most widely used owner-architect agreement in the United States. It governs everything from a small renovation to a large institutional project, and the way it classifies services determines what the architect gets paid for, what requires separate authorization, and where liability risk sits. The agreement splits all architect services into exactly three categories. Getting the boundaries between them right is a core practice management skill. ## Basic Services: The Five-Phase Foundation Basic services are the architect's core obligations under B101. They span five sequential project phases: 1. Schematic Design (SD) -- Establishing the general scope, scale, and relationships of the project. Conceptual drawings, preliminary code analysis, and an initial estimate of the cost of the work. 2. Design Development (DD) -- Fixing the size and character of the project. Drawings expand in detail to show architectural, structural, mechanical, and electrical systems. Consultant coordination ramps up.

Professional

Consider an architecture firm that signs a B101 agreement for a new community center. The base fee covers all five phases of basic services. During contract negotiation, the owner also requests programming services and site evaluation. Those get scoped as supplemental services under Article 4.1, with their own fee schedule attached to the agreement. Six months into design development, the city updates its energy code. The architect's DD drawings, prepared in compliance with the code in effect at the time, now need revisions. Under B101, code changes by authorities having jurisdiction that contradict the basis on which the instruments of service were prepared constitute an additional service. The architect sends a written request to the owner, outlining the scope of revisions, the hours required, and the fee. Only after receiving written authorization does the work proceed. This scenario plays out constantly in practice.

TLDR

Basic services = five phases (SD, DD, CD, Procurement, CA) included in the base fee. The architect is contractually bound to perform all five once the agreement is signed.
Supplemental services = identified and priced at contract execution, not part of basic services. Examples: programming, LEED certification, site evaluation, FF&E design.
Additional services = arise after execution. Require the owner's written authorization and separate compensation before the architect proceeds.
Timing is the differentiator: agreed at signing = supplemental. Arises mid-project = additional.
Fee benchmarks for basic services phases: SD 18%, DD 20%, CD 31%, Bidding 2%, CA + closeout 29%.
B104 compresses basic services to three phases (design, documents, construction) for limited-scope projects.
B102 has no predefined scope; parties attach whichever AIA scope documents fit.
Performing additional services without written authorization means the architect absorbs the cost.
RFIs not prepared per contract documents can entitle the architect to additional compensation under B101 Section 4.2.2.2.

ELI5

Imagine you hire a caterer for your wedding. The catering contract comes with a standard package: appetizers, main course, dessert, drinks, and cleanup. That's five things, and they're all included in the price you agreed to. In architecture terms, that's basic services. Five phases, one fee. Now, before you sign the contract, you also ask the caterer to handle a late-night snack station and a custom wedding cake. Those aren't part of the standard package, but you agree on them and their price before signing. That's supplemental services. Extra work, identified upfront, priced separately. Two weeks before the wedding, your guest count jumps from 150 to 250. You call the caterer and ask if they can scale everything up. They say yes, but it'll cost more, and they need you to sign off in writing before they start buying extra food. That's additional services.

AREPractice Management

B101 Basic vs Supplemental vs Additional Services

2 min read201 words

Three Categories of Architect Services Under B101

Understanding these three categories is critical for the ARE because scope creep, fee disputes, and professional liability exposure all trace back to how services get classified.

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