Large, newly built homes throughout Minnesota will come with an added feature next year — whether their owners want it or not.

A state mandate requiring indoor sprinklers in new homes 4,500 square feet and larger goes into effect in January. Homebuilders are grumbling about the new rule, calling it costly and unnecessary. But fire officials welcome it as a measure of relief at a time when they are struggling to recruit and retain volunteers.

The 4,500-square-foot measurement includes a basement, even it’s unfinished, so the rule will apply to many new homes sprouting in outer-ring suburbs or replacing teardowns in Edina, southwest Minneapolis and St. Paul’s Highland Park. About 30 percent of the new houses in the metro area meet or exceed that size threshold, according to the Builders Association of the Twin Cities.

Mark McNeill, Shakopee’s city administrator, sees the new rule as “a mixed bag.” He said he understands sprinklers’ safety value but worries that their added expense could make it harder for families with starter homes to move up to bigger new ones whose values can bolster a community’s tax base.

The job of making sure new homes meet the requirement will fall to city fire marshals or building inspectors. “We’ll obviously have to keep track of which houses require this when building plans are submitted for a permit,” said Dwight Picha, Woodbury community development director. But Picha said that the new requirement merely extends what city employees already do for large townhouses, where indoor sprinklers have been required for several years.

Homebuilders are dismayed. “That additional square footage is going to be really expensive for home buyers,” said Shawn Nelson, president of the builders’ group and owner of a Burnsville building and remodeling firm. Sprinklers could add at least $9,000 to the price of a four-bedroom, three-bath home and as much as $20,000 in houses with private wells instead of city water systems, the organization says.

Builders also believe sprinklers are unnecessary, since new houses already must have hard-wired smoke alarms. Nelson said builders are concerned that the added expense could snuff out demand for large new homes, which has fueled much of the postrecession rebound in the homebuilding market.

“Let’s not force it,” said Mike Devoe, president of Ryland Homes. Devoe said he has no problem offering sprinklers as an option but doesn’t believe they should be mandatory.

Devoe and other builders say they don’t believe most buyers are interested in sprinklers.

Curt Christensen, owner of Lee Lyn Construction in Watertown, said that in 35 years of building homes, he’s only had one buyer ask for sprinklers. “And that’s because he worked for a sprinkler company,” he said. Christensen said most buyers are unaware of the coming change, but he has spoken with some clients who’ve asked if floor plans can be trimmed under the 4,500-square-foot limit.

Help for firefighters

Fire officials differ on builders’ cost estimates for sprinklers and point out that over time homeowners can recoup the upfront expense through lower insurance premiums. They also say that while smoke alarms can alert homeowners, they don’t protect houses or belongings until firefighters arrive.

“There’s nothing worse than standing in the yard with an owner as they watch firefighters try to put a fire out that’s already fully involved — shooting out windows and doors — by the time we get there,” said Marilyn Arnlund, deputy fire marshal in Maple Grove.

Arnlund and other fire officials say modern homes are susceptible to fires that can spread quickly, mostly because of their lightweight wood ceiling trusses and floor joists. Open floor plans and petroleum-based construction materials and furnishings found in newer homes also contribute to fires that can burn hot and fast.

This summer, Chaska Fire Chief Tim Wiebe led city and state officials on a tour of a large house that was ravaged by a fire in late May. The occupants escaped unharmed, but the house was a total loss. The fire started in the attached garage and spread to the house, where it had a burst of combustion known as flashover.

“The furnishings, the kitchen cabinets, just vaporized,” Wiebe said. “We were very fortunate that nobody, including our firefighters, was in there.”

He said he’d like to see sprinklers in all homes because they provide a way to extinguish fires or keep them small. That’s important as departments like his cover a growing number of households even as it becomes more difficult to recruit and retain replacements for the stream of baby boomers now retiring.

Chaska’s fire department is supposed to have a staff of 44 but currently has a volunteer force of 35, Wiebe said. None of Maple Grove’s five stations is fully staffed, according to Arnlund.

In Eagan, where fire department staffing is at its lowest level since the late 1980s, the city is considering a plan to go from five stations — which it says it cannot fully staff — down to three. For now, it is bridging part of the gap in its volunteer force with a federal grant to fund some full-time, paid positions.

The Spring Lake Park-Blaine-Mounds View fire department also has used a federal grant to add a recruitment and retention coordinator. “We’re not understaffed now, but we can see we’re going to have turnover and want to get ahead of the curve,” said Maddison Zikmund, who has filled the position.

Zikmund said that even when there are enough volunteers, they’re not always in parts of town where they’re needed. “A lot of the people we get don’t live close enough to our stations,” he said.

As result, some cities are switching to duty crews, where volunteer firefighters are scheduled instead of being paid-on-call. Some communities are adding full-time paid positions. Both of those staffing models cost more.

Chaska City Administrator Matt Podhrasky believes the staffing challenges are part of larger change. “It used to be that volunteers would sign on and stay for 20 years, but we’re a lot more mobile now,” he said. “We just have to plan around it.”