$2.9m, is to come from grants, fundraisers and donations (scroll further down for more detail.)
The rest is to come from the council which plans to sell $1.6m worth of land and property reserves it owns across the district, and also use the money it currently spends on leasing a space for the public library.
The council has already committed $900,000 for the strengthening which will come from rates.
Paul Crimp said if council had not supported the project it was unlikely to get grant funding.
He said there wouldn't be impact on ratepayers and until funding from grants, donations etc, was finalised, any shortfalls were not known.
He said the project is staged so if there is a shortfall, further work can be delayed.
The Martinborough Town Hall working group's feasibility study can be viewed here.