Charminster Library remains closed following a partial ceiling collapse in December.
BCP Council says the building requires extensive repairs, but funding has not yet been secured.
Investigations found asbestos contamination, roof deterioration and redundant ceiling-mounted radiators, including one that had fallen.
The work needed includes asbestos removal, roof repairs, new ceilings, lighting and full internal and external refurbishment.
The cost is currently estimated at around £680,000, although final figures will depend on securing funding and contractor quotes.
If approved, the repairs are expected to take around 20 weeks.
In the meantime, residents are being directed to alternative libraries in the area, including Castlepoint and Winton.
Online services, including eBooks, audiobooks and digital newspapers, are also available.
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