"We expect net absorption to remain strongly positive in Orange County as demand reaches new highs throughout the remainder of this year and into next, a trend we are seeing in most of the larger office markets throughout the West," Pupil says. "Since Orange County is a medium-sized suburban market, it can be seen as an indicator of trends to come in other like-sized suburban office markets. It's a good litmus test."

Another indicator of the Orange County office market's relative strength, according to the report, was the rise in direct weighted average asking rental rates. Those rates during the 90-day period rose to $2.26 per square foot per month for full-service-gross leases, marking a 15% increase from the start of 2014. One of the reasons for the rise is that construction activity, once relatively constrained throughout the county, is on pace to potentially reach record levels. There are some 5 million square feet of office space in the planning stage, including more than 1 million square feet that has been designated as "speculative" space, or space to be built without committed tenants.

"Developers, once stung by the recession, are now approaching the market aggressively and are set to build both new traditional class-A space as well as renovate existing projects into creative-office space that is in high demand among tech and other service companies," Caudill tells GlobeSt.com. "This growing demand factor has caused major national developers to jump into the Orange County market with both feet. This could be the beginning of one of the greatest office growth cycles in Orange County in the past 20 years."

According to Caudill, those major office developers include the Irvine Co., Lincoln Property Co., LBA Realty, Bixby Land Co. and other national developers of office space who now view Orange County as a prime location for new, speculative space due to the high demand characteristics of the market, declining vacancies and the growth in employment.

Despite there being no new office developments delivered to the market during third quarter of 2015, levels of construction, which had been limited to three active projects during the three-month period ended September 30, are about to change, Caudill notes. On the vanguard of that change are two speculative projects: the Irvine Co.'s 425,000-square-foot development at 200 Spectrum Center Dr. in Irvine and Source Tower in Buena Park, totaling 72,300 square feet, including both ground-floor retail and office space.

With a target completion date of second quarter 2016, the Irvine Co.'s project consists of 21 stories and will be the first new office tower built in the Irvine Spectrum during the past seven years, the report notes. Source Tower, although much smaller, will add 72,300 square feet of class-A office and retail space to the heavily office-constrained Buena Park submarket when it is completed at the end of the fourth quarter.

Parker Properties, meantime, broke ground in June on a 205,000-square-foot office building at the Summit Office Campus in Aliso Viejo. However, that four-story project has been pre-sold to medical-technology firm MicroVention and is not expected to be completed until 2017. It is the final structure in the 14-building office campus that saw its first building completed in 1997 and that also houses such firms as Bausch + Lomb and Microsemi.

Meanwhile, in the investment market, Orange County witnessed a flurry of sales activity during the third quarter as investors raced to take advantage of low interest rates and per-foot prices that are expected to rise over the next three to six months, according to Colliers. Prices for existing properties slated for conversion to creative-office space are expected to top $300 per square foot during the next quarter and into 2016 based on fundamentally sound market conditions including a growing demand factor among tenants for such hybrid space. Class-A properties are expected to top $400 per square foot over the same time period.

As examples of the rising prices, Hines acquired the four-building Quintana Portfolio in Irvine for $284 per square foot and is converting it into creative-office space, the report notes. GEM Realty Capital Inc. acquired 1900 S. State College Blvd. in Anaheim for $260 per square foot from Kennedy-Wilson Properties, and Cornerstone Advisers LLC acquired 27442 and 27422 Portola Pkwy. in Foothill Ranch for $236 per square foot. The only example of existing space selling above those current prices was Prudential's acquisition of 1301 Dove St. in Newport Beach for $357 per square foot.

"When investors are this active in any market, it's a good sign that they believe the market is going to remain strong over the long term," Caudill says. "Big, institutional investors like this do not base their decisions on whims, but on solid research. It's a very positive sign for this market."

In terms of inventory and availability, tenants, especially those looking for spaces ranging from 5,000 square feet to 20,000 square feet, can still select from a wide range of options, the report notes. But there is a limited supply of larger, contiguous spaces.

"Where we are seeing this shortage is in the number of large blocks of contiguous available space greater than 100,000 square feet in size," Caudill says. "That size can be found currently in less than about seven to 10 projects in Orange County, and that number continues to decrease almost daily, another factor motivating developers and fueling new construction. If anything, it will be demand for spaces in this size range that will drive developers to start new spec projects."