Like life in general, careers sometimes take unexpected turns.

That certainly was the case for two 30-something sisters and a former corporate guy who now run local home improvement businesses.

Rachel Blum and Jaclyn Blum Guelfi didn’t intend to become partners in a specialty window and door operation. But after their dad died suddenly in 2010, that’s exactly what happened when they took over his Marin store, Window Factory. They knew that they wanted to keep it going.

The sisters realized it was going to be a “huge challenge,” given their lack of business expertise, said Rachel Blum, but how huge would come as a bit of a shock.

“We were somewhat sheltered,” said Blum, 33. “He was able to protect us from some of the roughest times.”

The sisters’ choice was clear: They could pack it in, or put all other commitments aside and move quickly to make it work.

At the dawn of 2011, when they took over the business amid the housing downturn and sagging economy, the home improvement industry was tanking. Many homes were underwater, and many of Window Factory’s competitors failed. Window Factory stayed afloat largely because their father, Leon Blum, had poured a lot of his own money into the business, said Rachel Blum. “He was tough, but at the end of the day, he took care of everyone who worked for him,” she said. “They were like family.”

To cut costs, the sisters consolidated the two-site operation into one location in Larkspur that would house the office, showroom and warehouse.

Blum had been working in commercial real estate and living in New York, where for eight years she lived a vibrant Jewish existence. It has not been as easy to live an active Jewish life in the Bay Area.

“Here, you have to make an effort,” she said. “My Jewishness is within my family, our culture.”

The sisters’ family history is a rich one: One set of grandparents comes from Russia; the grandfather is still alive. Their other grandparents fled Nazi Germany for the safety of Shanghai, where they would remain for 10 years before resettling in San Francisco. Their grandmother lives in San Mateo. (“I know she reads J. because she always clips out that ad for a matchmaker to show me,” said Blum, who is single.)

Blum Guelfi, 36, who is married and has two children, was no stranger to Window Factory, having worked for her father for several years. Still, taking over the business with her sister involved a steep learning curve.

But the sisters’ efforts, boosted by the improving economy, have paid off. “Consumer confidence has really risen,” Blum said. “People are putting money into their homes with the idea that they want to stay put.”

With window and door projects in mind, the sisters have some practical advice for homeowners:

• A window is only as good as its installation. Get a contractor who specializes in windows and carries an installation warranty.

• Choose a glass package on new windows or doors that includes Energy Star-rated, Low-E glass (an energy-efficient, treated glass that conducts visible light while controlling the passage of heat into and out of a home).

• Take advantage of the federal tax credit that will expire at the end of 2013 (10 percent, up to $500 for Energy Star-rated windows and doors).

• Choose a brand that comes with a transferrable warranty. That could carry some value if you decide to sell your home.

Another family business run by a Jewish team who redirected their careers is HOUSEworks in San Francisco. Former financial services executive Jeff Kann made the jump to a new career in 2005.  Buying and remodeling four homes (and working his way through college on a construction crew) had piqued his interest in home improvement. Ellie Kann, to whom he has been married for 25 years, handles marketing for the company and coaches girls’ varsity tennis at Acalanes High School in Lafayette.

The couple, who have two grown children, are active members of Temple Isaiah in Lafayette.

HOUSEworks, which Kann founded, is a residential design and build contracting firm. It was named a 2012 Big 50 remodeler by Remodeling, a trade magazine. The annual award is given to the top 50 firms that exemplify high standards in the industry.

Homeowners and contractors can cause projects to run over schedule and budget by planning unrealistically, noted Kann. That’s important to know, he said, since the only opportunity to save money and time is during planning.

The most common mistakes?

• Hiring the wrong people for the job.

• Designing a project without knowing how much it will cost to build.

• Starting construction before planning is completed.

• Overreacting to problems during construction.  

“The horror stories you have heard about result from a lack of careful planning and execution of these things that result from the various participants not working together — often not even talking to each other,” Kann said.

He also cautions consumers to beware of cost-cutting maneuvers that can backfire, such as using cheaper but inferior materials, poorly skilled employees and bad project management.

There are ups and downs over the course of the project and even if everything is completely planned out in advance, despite everyone’s best efforts, things may still go wrong, he cautioned. This may throw the homeowner, but professionals “are used to solving problems on the fly, revising a schedule or putting out fires as part of every job,” he said.

In his opinion, the projects that bring about the greatest satisfaction are those that improve lifestyle, such as creating a family gathering space — usually opening walls between kitchens and family rooms — and adding bedrooms or in-law suites for multigenerational living, Kann has found. That is increasingly important in cases where families care for aging parents, he said.