Architectural billings index at 44.7: where to send spec reps in 2027

Billings at US architecture firms fell to 44.7 in September 2026, down from 47.2 in August, according to AIA’s Oct. 21 release on the September architectural billings index. AIA and Deltek call it the Architecture Billings Index, or ABI. A score under 50 means more firms reported falling billings than rising ones, and AIA said September had the largest share of firms reporting declines since May.

For a building products manufacturer selling into nonresidential jobs, the national score is the least useful number in the release. AIA’s regional and sector scores have traded places since January. Commercial/industrial firms and the West and Midwest now sit just above 50, while the South, multifamily and the Northeast have weakened. Our position is that spec calls, lunch-and-learns and CEU outreach in Q1 and Q2 2027 should move toward commercial/industrial firms in the West and Midwest, and multifamily and Northeast firms should be run as maintenance accounts.

What changed in the architectural billings index between January and September 2026

AIA’s January 2026 ABI release, published Feb. 18, and its September release both state that the regional and sector scores are calculated as three-month moving averages. That puts the two months on the same basis, so we lined them up.

AIA score (three-month moving average)	January 2026	September 2026	Change
West	46.3	50.7	+4.4
Midwest	46.3	50.6	+4.3
South	50.2	43.1	-7.1
Northeast	42.3	39.1	-3.2
Commercial/industrial	43.9	50.9	+7.0
Institutional	46.8	47.6	+0.8
Multifamily residential	48.4	42.9	-5.5
Mixed practice	43.4	41.5	-1.9

Source: AIA/Deltek Architecture Billings Index, January 2026 (released Feb. 18, 2026) and September 2026 (released Oct. 21, 2026). Change column is our arithmetic.

In January the South was the only region holding steady. By September it was the second weakest. Commercial/industrial went from the lowest of the three named sectors to the only one above 50, with growth for “a second consecutive month,” in AIA’s words.

Keep the size of the move in proportion. AIA’s September ABI summary describes the West and Midwest as flat and commercial/industrial growth as slight. Flat is still the best showing in a market where most firms are shrinking. The same summary says institutional billings have declined for six consecutive months and multifamily for five. This is also a two-point comparison, January against September with no months in between. It shows where each score has landed, and it cannot prove a steady trend.

Why billings at architecture firms matter to a product manufacturer

AIA’s ABI program page says the index predicts nonresidential construction activity 9 to 12 months ahead. AIA makes no claim about building products or specifications, so connecting billings to product selection is our own argument.

Billings measure design work underway now, and that is the stretch when products get named in drawings and specs. Two other readings sharpen the picture. AIA’s September release shows more owners asking about projects than signing them, and backlogs shrinking. January’s index values below come from the Feb. 18 release.

AIA indicator	Earlier reading	September 2026
Project inquiries index	49.3 (January 2026)	53.2
Design contracts index	42.7 (January 2026)	43.7
Average firm backlog	6.6 months (end of Q1 2026)	6.2 months (end of Q3)
Multifamily firm backlog	6.2 months (March 2026)	4.8 months

Source: AIA/Deltek Architecture Billings Index releases of Feb. 18 and Oct. 21, 2026.

Our reading is that the projects specified in 2027 are being shaped now inside fewer firms, each competing harder for work. AIA’s panel says as much. “There are opportunities out there, but there is increased competition,” a 60-person Midwest firm with an institutional specialization told AIA in its September summary. When design work is scarce, a spec rep’s calendar is the constraint, and it should follow the sector and regional scores.

Do construction starts and contractor backlogs agree?

Partly, and the differences are about timing. Dodge Construction Network’s September starts report had nonresidential building starts down 6.3% for the month to a $583 billion annual rate, though up 23.7% year to date. Commercial starts fell 18.4% from August but were up 47.7% over 12 months. The three largest projects to break ground were data centers in Nevada, Texas and Virginia.

ABC’s Construction Backlog Indicator for September, released Oct. 13, rose 0.2 to 8.7 months, its second straight monthly gain, with commercial and institutional backlog at its highest since July 2025. Contractors with data center work averaged 11.3 months.

Starts and backlog describe jobs already designed, while the ABI tracks the round still on the drawing board. Dodge’s regional figures are total starts across all sectors, residential and civil included, so we leave them out of the regional argument. If data centers are a real target for you, that is its own sales motion, covered in our data center piece.

Where to put spec selling time in the first half of 2027

Start with the account list. Tag every architecture firm your reps call on by region and by majority sector, using AIA’s rule that a mixed-practice firm is one without at least half its billings in any single category.

Then move the calendar. Before Q1 lunch-and-learn and CEU slots fill, shift a fixed share, a third is a reasonable start, from multifamily and Northeast firms to commercial/industrial firms in the West and Midwest. Point your AIA course promotion the same way. If you sell only in the Northeast or the South, the regional half of that shift does not apply to you; move the same share toward commercial/industrial firms inside your own territory.

Maintenance accounts still get attention. Keep multifamily and Northeast firms on a quarterly check-in, support every live spec so it survives value engineering, and answer substitution requests the same day.

On every architect call, ask how many inquiries the firm has open and how many have become signed contracts. That gap is AIA’s national story, and it shows you account by account who is about to start design.

Recheck the regional and sector scores when AIA publishes October and November data, and adjust territories before the Q2 calendar locks.