The AIA/Deltek Architecture Billings Index for April 2026 came in at 48.3, down from 49.8 in March. That one-point decline extends an already historic streak: according to Calculated Risk's analysis of the April data, architecture firm billings have now contracted in 42 of the last 43 months — the longest sustained period below the 50-point growth threshold since the index entered its modern tracking format. For a metric that typically leads commercial real estate investment activity by 9 to 12 months, the data carries direct implications for the nonresidential construction pipeline into 2027.

What the ABI Measures and Why It Matters

The AIA/Deltek Architecture Billings Index is a monthly diffusion index based on a survey of U.S. architecture firms. A score above 50 indicates that more firms are reporting billing increases than decreases; below 50 indicates the reverse. Because architecture services typically precede construction by 9 to 18 months — design work, permitting, and procurement must precede a construction start — the ABI is widely used as a leading indicator for nonresidential construction activity. A prolonged period below 50 does not mean construction stops; projects already in the pipeline continue. But it signals that the flow of new work entering the design phase is insufficient to sustain construction volume at current levels through the following year.

AIA Chief Economist Kermit Baker noted that the April decline reflects "broader economic instability" that is causing owners to hesitate at the design stage. The April score of 48.3 marks the 39th month below 50 in the series as of April data (the Edison Report's count differs from Calculated Risk's due to the definition of the streak's start; both reflect a prolonged contraction beginning in early 2023). National architecture firm billings have not crossed the 50-point growth threshold since January 2023 — a period that spans the full post-pandemic interest rate normalization cycle.

The Regional Picture

Regional ABI performance for April 2026 shows the contraction is broad-based but not uniform. Residential Design Magazine's summary of the April release reports regional averages as follows:

• West: 49.0 — closest to flat among the four regions, reflecting residual strength in Pacific Coast markets and data center design activity in Nevada and Arizona
• Midwest: 48.0 — dragged by slower commercial and office activity, partially offset by healthcare and institutional design work
• South: 47.7 — weakest of the sunbelt-heavy regions, a notable reversal from its outperformance in 2021 through 2023
• Northeast: 47.2 — lowest of the four regions, consistent with tighter financial conditions, slower office market recovery, and elevated construction costs

No region is currently reporting growth-threshold billings, meaning the leading indicator for new nonresidential project flow is negative across all four major U.S. geographies simultaneously.

Where Billings Are Growing: The Exceptions That Prove the Rule

The April sector breakdown reveals the same bifurcation visible in construction spending and employment data. According to the AIA's April sector indices:

• Multifamily residential: 51.5 — above the growth threshold for the second consecutive month, the first back-to-back expansion in this subcategory after 43 consecutive months of contraction. The multifamily recovery is modest but notable given the depth of the prior correction.
• Institutional: 51.1 — above 50, driven by healthcare facility design, higher education, and public sector projects that are less sensitive to commercial real estate financing conditions
• Commercial/Industrial: 48.9 — below 50, reflecting weakness in office, retail, and conventional commercial development that is only partially offset by data center and advanced manufacturing design activity
• Mixed practice firms: 42.5 — the lowest reading across all categories, suggesting that generalist architecture firms without concentration in growth sectors are experiencing the most severe billing deterioration

The institutional and multifamily readings above 50 are meaningful. Healthcare construction remains one of the most active nonresidential sectors nationally; the same Census Bureau data showing weakness in commercial construction shows hospital and medical facility spending at elevated levels. Multifamily's recovery to positive billing territory, even modestly, aligns with the April 2026 Census data showing multifamily housing starts at a three-year high of 529,000 units annualized.

The Cost-and-Financing Squeeze at the Design Stage

The deeper story behind 42 months of ABI contraction is the combination of elevated construction costs and financing constraints that is causing owners to hesitate or abandon projects at the design phase. Mortenson's Q1 2026 Construction Cost Index documents that nonresidential construction costs rose 1.69 percent quarter-over-quarter and 6.77 percent year-over-year, with advanced manufacturing and data center demand absorbing labor capacity and driving up costs across all nonresidential subcategories. The 30-year fixed mortgage rate is now near a one-year high, financial markets are pricing in a roughly 60 percent chance of at least one rate increase by year-end, and commercial real estate financing remains constrained relative to pre-2022 conditions.

ConstructConnect Chief Economist Michael Guckes described the owner-level dynamic in June 2026: developers are asking about and designing projects, but as soon as they confront current cost estimates, budgets, and financing terms, they "get a case of the yips" — either slowing the project or abandoning it entirely. AIA Chief Economist Richard Branch (who has also contributed analysis to ConstructConnect's Spring 2026 Outlook) noted that "real construction activity — boots on the ground — has been flat at best" in the non-residential building space when adjusted for inflation and sector composition. The architecture billing index is capturing exactly this dynamic: the decision to commit to design work is being deferred at a rate that has not been seen since the 2008 to 2010 correction.

What the Pipeline Looks Like From Here

The 9-to-12-month lag between ABI readings and construction starts means the April 2026 data is most predictive for nonresidential construction activity in approximately the first quarter of 2027. The persistent sub-50 readings throughout 2025 and into 2026 suggest that the project flow entering the construction phase in the second half of 2026 and through early 2027 will be constrained for most subcategories outside of data centers, healthcare, multifamily, and public infrastructure. Those sectors — supported by federal funding, healthcare system capital cycles, and AI-driven technology investment — are largely operating outside the commercial real estate financing dynamics that have suppressed ABI readings since January 2023.

For contractors dependent on conventional commercial and office work, the ABI data is a directional signal that project flow from the design pipeline will remain lean. For those with capacity in data centers, healthcare, institutional, and multifamily, the two subcategories above 50 in April indicate that the leading-indicator flow for those segments is at least stabilizing. The broader nonresidential construction market remains divided between a small number of segments experiencing genuine demand growth and a much larger number of subcategories where the pipeline is thinner than headline construction spending figures suggest.

Sources

• Edison Report, AIA ABI Declines for 39th Consecutive Month (May 20, 2026)
• Calculated Risk, Architecture Billings Retreat in April (May 20, 2026)
• Residential Design Magazine, AIA/Deltek ABI: Architecture Firm Billings Retreat in April (May 21, 2026)
• Mortenson Construction Cost Index Q1 2026 (June 2, 2026)
• ConstructConnect, June 2026 Data Center Report (May 27, 2026)