A Suffolk County company that helps Walmart, Staples, Macy’s and other retail chains maintain their stores is planning an $11 million expansion in Hauppauge.

Broadway National Group LLC wants to purchase and renovate 100 Davids Dr. for use as its headquarters. The company now operates from a smaller building in Ronkonkoma.

Last week the Suffolk County Industrial Development Agency endorsed the project with $1 million in tax breaks, including $733,750 off property taxes, or a 26.5 percent savings over 15 years.

In return Broadway National pledged to add 50 people to the company’s workforce of 101 by 2020.

“Our business is growing so rapidly . . . and we really only see the future getting brighter,” said William E. Paparella, the company’s CEO and founder.

Broadway National’s revenue has climbed from $1.4 million in 2004 to a projected $48.3 million this year.

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The privately held company’s payroll has risen from 63 two years ago, according to documents given to the IDA. Records show that employees earn, on average, $53,675 per year, excluding medical insurance and retirement benefits.

Paparella said retailers, banks, fashion houses and others hire Broadway National to oversee building maintenance, including snow removal, landscaping, heating and air conditioning, plumbing and other repairs. He and his staff then make arrangements for contractors to do the work.

Broadway National provides software to its clients so they can monitor repairs, improvements or other work on their properties. This technology has helped fuel the company’s growth, Paparella said.

Broadway National has satellite offices in Arizona and Tennessee, and the company plans to open one in North Carolina later this year.

Paparella said that without help from Suffolk he would have to move the company’s headquarters off Long Island, where the business started in 1989 as a manufacturer of store signs in his parents’ garage.

“I’d like to keep the heart of the operation on Long Island,” he said. “However, we are always under a competitive threat because my competitors are typically in other areas of the country” where the cost of doing business is lower.

Paparella said Broadway National also needs assistance from New York State.

Amy Varghese, a spokeswoman for Empire State Development, the state’s primary business-aid agency, said yesterday, “We stand ready and willing to hold discussions with any company that shows an interest in New York State.”

The owner of the Davids Drive building that Paparella wants to buy, the Narda-MITEQ division of defense contractor L3 Technologies, received help from the state and Suffolk recently after threatening to move 142 jobs from Hauppauge to New Jersey. L3 is transferring its Davids Drive employees to its other facility on Moreland Road in Hauppauge.