Work on a £1.15m MS therapy centre in Bradley Stoke near Bristol is to begin by the end of May.
The centre was under threat after it discovered fibre optics and a gas pipeline beneath a planned access route would cost £1m to divert.
The route was moved to a nearby residential road, which sparked complaints from residents.
But the charity behind the centre has now signed a deal with a building firm allowing work to get under way.
Mike Gelder, from the Moonstone Appeal, said the charity was short of some of the money to fund the move from its current home in Nailsea.
"The situation is that we have got all of the money required to build but we still need about another £80,000 for us to fit it out and fund the move.
"If we hadn't proceeded we would have lost £400,000 in grants at end of the month so it's a bit of a risk."
He said the charity was now starting several schemes to raise the shortfall in funds, including sponsorship appeals.
Mr Gelder said the building work would be "sensitive" to neighbours on Wheatfield Drive.
"We've picked the method of working that means a lot of work is carried out off site and it comes in pre-made.
"They'll be dropping the pieces over from Bradley Stoke Way [the main road] and over the fence."
The West of England MS Therapy Centre was built in Nailsea in 1985 to provide support and help with the relief of symptoms.