Vacancies are rising in Miami-Dade (16.2%), Broward (20.8%) and Palm Beach (14.1%). But the worst is yet to come, predicts a new analysis by the Fort Lauderdale, FL office of Cushman & Wakefield of Florida Inc.

A total 1.3 million sf of speculative space is under construction on Brickell Avenue, Coral Gables and Miami Beach.

Brickell Avenue, Miami's financial district, could be in for a shock as 236,000 sf becomes vacant over the next 15 months. About 44% of the 236,000 sf is sublease space.

At 12.6%, the Brickell submarket has enjoyed one of the lowest vacancy rates in the county. Vacancy levels could jump by four percentage points.

The hardest-hit property is expected to be the 1111 Brickell Avenue building where London-based Barclays Bank will vacate 75,000 sf over the next 12 months.

"The increase in available space, coupled with the 485,000 sf under construction to be completed next year, will undoubtedly raise vacancy rates to the highest levels in more than four years," the report predicts.

An increase in space availability on Brickell Avenue could hurt the Coral Gables submarket which has been absorbing the overflow from Brickell and Downtown over the past few years.

Coral Gables enjoyed direct first-quarter absorption of 102,575 sf. Brickell had a negative 23,099 sf; Downtown, a negative 72,839 sf. The recently completed 174,305-sf Alhambra Towers helped Coral Gables' absorption numbers by opening with a 70% occupancy.

Despite the rising vacancy levels, rents are also heading upwards. Quoted class A space on Brickell Avenue is $32.79 per sf; Downtown, $32.18 per sf.

Outside the central business district, quoted rents are $31.74 per sf in Coral Gables; $25.02, Airport/West Dade; $25.24, Kendall/South Dade; $24.18, Miami Lakes; $30.19, Coconut Grove; and $34.82, Miami Beach. The average quoted rent in Miami-Dade is $28.34 per sf.