This spring residents will be asked to weigh in on the design of a new park on a 1.2-acre parcel at 771 North Rengstorff Ave., and along with it, help seal the fate of the city's smallest historic home, the Immigrant House.

The Friends of the Immigrant House have garnered some enthusiastic support of the community behind efforts to save the 400-square- foot house -- which may be 150 years old -- as an example of the tiny homes migrant workers once lived in. But some uncertainty around restoration costs and its final use has made fundraising a challenge.

Marina Marinovich -- granddaughter of some former residents of the tiny house and leader of the effort to preserve it -- said $62,000 has been raised so far, including $50,000 that Google donated early last year. But since then, Marinovich said, some grant requests have been turned down without a detailed list of restoration costs from the city.

Also raising concerns is that the city had an estimate done in 2012 that put the price of restoring the home at $227,000. The Friends of the Immigrant House are being asked to raise half the final cost, and donors are asking why the estimate is so high.

"Without an itemized description of what is being funded, they really don't feel comfortable funding it," Marinovich said of some potentially significant donors. "We got denied two grants because of that. I'm going to continue doing fundraising no matter what, but people are asking me why it's so much and I have no answer for them. If it really does cost that, then I guess it's OK."

Also raising eyebrows is that the city of San Jose restored four similar "migrant cabins" for just over $127,600 a few years ago for Kelley Park, including $40,000 in donated architect fees. If the Mountain View house is in similar shape, that would put restoration costs closer to $20,000, as Marinovich said local architects have also offered to donate their time to the project.

Public works officials were hesitant to immediately reveal the details of the 2012 estimate -- done for free by a contractor the city is familiar with -- to the Voice or anyone else. Another cost estimate will be made after the public planning process this spring, but deputy public works director Jacqueline Solomon said of the estimated cost: "I don't see how it could go down, because it was just to make it structurally sound and because it was in such poor repair. If you are building it from scratch, that's one thing, but when you are trying to restore it, that makes it that much more complicated."

She added that the 2012 estimate was "pretty detailed" and put the construction costs at $170,000, with the rest going to cover "project management and construction management, building permits, that sort of thing."

The city had previously imposed a deadline on the fundraising that would have meant all funds were to be raised by this month. B on Dec. 9 City Council members unanimously approved an extension for fundraising for the house until September, after public works director Mike Fuller explained the situation. "Until they can demonstrate to prospective donors the context of the house and what that use might be, they are having trouble raising more funds." He added that it will be up to the council whether to extend the deadline any further.

The Kiwanis Club has been involved in funding the house, and Nick Galiotto, past president of the club and former Mountain View mayor, described the hangup this way: "The actual use of Immigrant House is to be determined through the city process, yet potential funding sources need to know that end use."

The Friends of the Immigrant House would prefer that the structure be used as a static display with period-correct interior and furnishings so people can get an idea of how migrant workers once lived in it. But the possibility has been raised that the tiny house would be used for other functions, possibly as some sort of gathering space.

At the Dec. 9 meeting, council members also approved $168,100 for Callandar Associates to design the new park at 771 Rengstorff Ave., with public input this spring. Last year residents expressed support for a community garden there, and for maintaining much of the fruit-bearing trees, bee hives and the vegetable garden on the site, previously owned for many decades by the Stieper family. The Stieper family home was left standing on the site at the request of the council in case there is a clear desire from the community to make use of it.

Tax-deductible donations to the Immigrant House can be made here.