When replacing balusters or spindles on a staircase, pay attention to spacing. If they’re too far apart they might not meet building code – and might be a threat to toddlers.

That was the message from a reader after a story in early September about updating staircases. It’s sound advice, of course – and timely. Turns out the interior staircase code was tightened a bit recently.

Also, it turns out, the baluster replacement expert featured in the story agrees with the reader. “Great topic,” said John Zeidner of Staircase Transformations. “Conforming to code is important and therefore not all staircases are viable candidates for transformations in the ‘retrofit’ style ... I probably walk away from about 30 percent of prospect inquiries for this reason.”

The code covering interior balusters was tweaked on March 1, according to the helpful folks at the RTAC desk operated by Mecklenburg County Code Enforcement.

The code now says that a 4-inch sphere can’t pass between balusters on an interior staircase. That eliminates some of the gray areas in the previous code.

There’s still an exception for balusters under guard rails, where the opening can be 4 3/8 inches, which RTAC says is a sort of fudge factor.

The logic behind the code is that 4 inches should be small enough to keep a child from poking his head between the balusters.

But staircases vary. Some stairs have two balusters per step, some – with deeper threads – have three.

Zeidner said many older homes don’t meet the rule. They have gaps wider than 4 inches. In such cases, he typically declines the job.

In other cases, replacing a wooden baluster with a metal version that’s much slimmer would make the gap wider than the original.

Zeidner says he tries to maintain the existing gap by choosing the proper thickness of iron replacement baluster. “The spacing is not more than previous and sometimes even less. This costs more for the materials but is always a worthwhile investment.”

As the Sept. 8 story said, baluster replacement is a popular do-it-yourself project. You can buy components online and at your nearest home center.

Questions? Call the RTAC desk at 704-432-7822. RTAC stands for Residential Technical Answer Center. It’s always a good place to start. Specialists are available weekdays 8 a.m.-5 p.m.

The updated code is also online. Go to the RTAC page on the Code Enforcement site – charmeck.org/mecklenburg/county/CodeEnforcement/ResidentialBuilding/Pages/RTAC.aspx – and click on the “E-codes” link.