Fair housing advocates are challenging a component of the Walsh administration’s new version of an Inclusionary Development Policy (IDP), claiming the boundaries of “affordable” rents are pushed to heights which will exclude families reliant on housing assistance. The City asserts that only limited exceptions could be made for such developments, leaving most of the rent levels unchanged.

In Zone C, which comprises Dorchester, Roxbury, Mattapan, Hyde Park and West Roxbury, tenants are eligible for IDP rental units if they make up to 70 percent of Area Median Income (AMI). The IDP also allows for the possibility of allowing construction of units for earners up to 100 percent AMI.

“The 70 percent AMI in Zone C will remain in place unless a project is deemed to be infeasible without some small concessions,” said housing chief Sheila Dillon. Ideally, those cases will be few and far between, she said.

Section 8 vouchers, crucial for many low-income families, help supplant some of the housing cost. While they can be applied to market-rate and affordable units alike, maximum rent prices limit the properties for which Section 8 vouchers can be used.

A Boston family of two would meet 70 percent AMI if they earned $55,150 annually, according to the Boston Redevelopment Authority’s (BRA) 2015 income metrics.

At 70 percent AMI, the maximum affordable rent for a studio apartment would be $1,068, which would be within reach of the Section 8 allowable rent ($1,315 as of 2014 calculations through the Boston Housing Authority). However, at 80 percent AMI or higher, using a Section 8 voucher would be difficult, and at 100 percent AMI, likely impossible.

“A person with a mobile Section 8 certificate does have options in the market,” Dillon said, acknowledging that it would be “tricky” in affordable units once AMI passed 80 percent.

“100 percent of AMI is way too high,” said Kathy Brown, coordinator with the Boston Tenant Coalition. “It’s getting tougher and tougher for people to apply their Section 8s.” By raising acceptable AMI in the city’s lowest-income zone, Brown fears that displacement risks and rents would increase.

She added that there were parts of the IDP that were beneficial, including a developer payout system.

The tenant coalition’s lawyer, Margaret Turner with Greater Boston Legal Services, said the Section 8 voucher users overlap with marginalized communities -- communities of color, the elderly, the disabled, and woman-headed households.

“There is huge disparity in incomes of households of color in Boston,” Turner said. “They are disproportionately excluded from the market rate housing.”

Dillion agreed that there are groups without unequal income levels, but said, “We don’t build housing for one demographic. We build housing for low income households, regardless of race.”

The City’s stance is that there is a hard line drawn at the 70 percent mark, and the processes for getting a project underwritten at a higher percentage would be “stringent,” Dillon said. Dillon could not estimate how many new housing starts might be approved at that higher rate.

Brown said this was not a point on which the tenant coalition would be flexible.

“We understand that it’s not in all cases, thank goodness, but we don’t think it should be in any case,” she said.