Insurer National Interstate Corp. said it soon will start building a $25 million office building on its Richfield campus.

Wednesday’s announcement follows the authorization Monday of Ohio Job Creation Tax Credits for the project.

National Interstate said it will put up a 117,000-square-foot office building for subsidiary National Interstate Insurance Co. that will allow the company to add 200 jobs to the more than 500 it now has in Richfield. This will be National Interstate’s third building.

Construction is expected to start in the last three months of the year and be finished in 2017, the company said.

In a news release, Tony J. Mercurio, National Interstate’s president and chief executive officer, said the project demonstrates the company’s commitment to Northeast Ohio.

“With our significant growth over the past several years, we need to continue to hire talented employees and that creates a need for additional office space,” he said.

National Interstate sells insurance for passenger, truck, and moving and storage transportation companies.

The Ohio Tax Credit Authority on Monday said National Interstate will receive tax credits totaling an estimated $1.77 million over seven years if it creates 217 jobs.

National Interstate said it expects to generate nearly $14 million in new annual payroll with the new jobs by Dec. 31, 2020. Current annual payroll in Richfield is $33 million.

National Interstate also needs to maintain operations in Richfield for at least 10 years.

National Interstate Corp. is being bought by its majority shareholder, Cincinnati-based American Financial Group, also known as AFG.