The Stepping Stones group is desperately searching for new premises after being told it must leave the Christchurch Centre in Milman Road, Katesgrove, by the end of the year.
The Christchurch Centre Trustees, who operate it on behalf of the Oxford Anglican Diocese, served notice in preparation for when Reading Borough Council submits a planning application to expand New Christchurch Primary School next door.
The school, has 188 pupils on its roll, but will reach its 210 capacity by September 2014 and the proposals, likely to be submitted next month, include building two new classrooms to free up space on the original school site for PE, drama and music.
Stepping Stones has used the centre for 12 years and caters for 148 members. Manager Debbie Grey, who has been working with the council on a suitable move since May, said: "We are hopeful that it will work out and we should know the result of our meetings with them by the end of August .
"If it does not we are very concerned about our future and where we will continue to work from."
Katesgrove councillor Matt Rodda supports the expansion plans but is worried about traffic congestion in the area and believes more should be done for Stepping Stones. He said: "They are vulnerable people who need to be thought about more carefully. They need to make sure if there is a change of building it's done sensitively for people who use it."
Trustees spokeswoman Sarah Meyrick said they had enjoyed a "fruitful" association with Stepping Stones but added: "Unfortunately, it has become impossible to maintain and repair the centre to the required standard under the current financial arrangements and we have taken the difficult decision to serve notice to Stepping Stones.
"As trustees it is our duty to ensure the centre's future, and we are therefore pleased to be entering into a partnership with New Christ Church School and the council."