Woolmers Estate chairman Peter Rae said a collaboration between the two Northern World Heritage sites, National Trust and councils could result in a popular heritage trail.

"We could have a winery tour in the Tamar Valley to the north of Launceston and a heritage tour to the south," Mr Rae said.

"It would make a good day trip and would be fairly easy to pull together. You could possibly visit Evandale and Franklin House on the way back to Launceston," he said.

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As World Heritage listed sites, Woolmers Estate and Brickendon attract federal and state funding to preserve and present the venues, Mr Rae said.

Seven National Trust of Australia (Tasmania) properties need almost $4 million in capital works, with managing director Matthew Smithies saying some were in danger of closing without "significant investment".

Clarendon is one of the properties in need of attention, with more than $1.5 million sought to cover drainage, foundation and footing treatment, wall repairs, consultancy and more.

Mr Smithies has written to state and federal government representatives outlining the extent of the conservation and restoration works needed at the seven properties and received a grant from the Tasmanian government, but it is not enough to cover what is needed.

Tourism Industry Council Tasmania chief executive Luke Martin said National Trust's request for funding was a "positive step".

"The challenge to maintain heritage is really difficult; it's relentless," he said.

"National Trust needs to present the economic opportunities for Tasmania."

Mr Martin said the state's built heritage sites had parallels with its national parks as both were part of Tasmania's brand and contributed to the economy.

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