A quarter of a million pounds needs to be raised this year to repair the spire at St Wulfram’s Church - despite the £272,000 grant from English Heritage announced last month.
The money needs to be in place so that the repair work can begin in 2014.
Church architect Graham Cook (pictured), of Beacon Lane in Grantham, said £250,000 still needs to be raised by the end of 2013 - although £40,000 has already been raised locally.
At least 100 potential grant sources are being approached.
Once the money is in place further investigations must be carried out, specifications for the building work must be agreed with English Heritage and the diocesan authorities and the work will then be opened up for tender.
Mr Cook said: “The dismantling and rebuilding work will take all of the time between early spring and late autumn 2014; the work having to be completed by the time the winter weather arrives in late autumn as we are using lime mortar which needs time to cure properly before it is exposed to hard frost.”
Steps are being taken to ensure the work does not interfere with the peregrine falcon nesting at the top of the tower this year.
The SOS banner flown from the tower will also need to be taken down for the duration of the nesting period.