Residents in Clontarf are up in arms over plans to turn a former nursing home into a homeless shelter and drug treatment centre.
Dublin City Council has granted permission for a "change of use" of the old La Verna nursing home on Haddon Road.
The 22 bedroom facility will house 50 residents and will be operated by Dublin Simon Community.
Residents have vowed to appeal the decision to grant permission to the High Court.
They say there is already a concentration of such facilities in the area, with five already in operation.
Locals also say there was a lack of consultation with residents who live nearby.
Door-to-door collections have started in the area for a legal fund for the appeal.