Led by the commercial sector, the architecture billings index remained in positive territory in February for the fourth-straight month, according to the American Institute of Architects.

The index also received the highest spike in inquiries for new projects since 2007, the year the housing bubble burst and a year before the nation's financial crisis.

The billings index, a leading economic indicator of construction activity, reflects the approximate lag of nine to 12 months between architecture billings and construction spending.

The February billings score was 51 following a mark of 50.9 in January, reflecting a slight increase in demand for design services.

Scores above 50 indicate an aggregate increase in billings, and scores below 50 suggest a decline.

The new projects inquiry index was 63.4, up from 61.2 in January — its highest reading since July 2007.

“This is more good news for the design and construction industry that continues to see improving business conditions,” AIA chief economist Kermit Baker said. “The factors that are preventing a more accelerated recovery are persistent caution from clients to move ahead with new projects and a continued difficulty in accessing financing for projects that developers have decided to pursue.” 

The Midwest had the highest billings reading at 56, while the West had the lowest at 45.6.

The commercial/industrial sector (55.1) led the national index, followed by multifamily residential (53.3), institutional (50.3) and mixed practice (46.3).

The regional and sector categories are calculated as a three-month moving average, whereas the index and inquiries are monthly numbers.

Results are seasonally adjusted to allow for comparison to prior months.