English Heritage has expressed concern over the preservation of historic Methodist chapels in Cornwall.
It warns that many of them are at risk of decay and closure as a result of long-term maintenance problems and ageing congregations.
Cornwall has one of the highest concentrations of Methodist and Nonconformist chapels in England.
Most of the chapels date from the 19th century and include among them 184 listed chapels - 30% of the national total.
Eighteen of the chapels are listed at Grade II* because of their rarity and historical significance as outstanding examples of their type.
One chapel, the Quaker meeting house at Come-to-Good, Kea, is listed at Grade I.
Many of the chapels sprang up after Methodism took root from the late 18th century. When Cornish people started to migrate to Australia, the Americas and other parts of the world in the 19th century, they also took their religion with them and built chapels to serve their new communities.
Joanne Balmforth, Conservation Officer for the Methodist Church, said: "We are extremely proud of the built heritage and legacy resulting from the Methodists presence in the Cornwall area."
Although over 900 chapels have been recorded in Cornwall, fewer than 250 of them remain in religious or community use.
The majority of the others have been converted for different uses, often domestic.
English Heritage warned that the distinctive character of the buildings may be lost in conversions if their special features are removed or hidden.
New guidance has been produced by English Heritage in partnership with the Methodist Church and Cornwall Council to help communities safeguard the character of chapels where their use may be changing.
Ms Balmforth continued: "We support the use of this guidance to conserve what we consider to be buildings of exceptional quality, often retaining intact interiors of significant national interest.
"We welcome this guidance as a serious attempt to inform and guide those with an interest in the conservation of Nonconformist chapels, whether it be managing sensitive alterations to extend their use, or in finding a sustainable and appropriate new use if the building is no longer in use as a place of worship."
The guidance can be found on the English Heritage website here
Jeremy Lake, English Heritage expert and co-author of the new guidance, said it would help owners, estate agents and communities manage "sensitive change" to chapels as well as find a sustainable future for the most significant and vulnerable ones.
"The greatest number of chapel closures within the Methodist Church is in Cornwall, and in coming years more chapels will close and be sold with many being converted to residential housing," he said.
"The challenge with those that remain open is how to maintain them while for those that close it is to find appropriate new uses for them that respect, so far as possible, their interiors."
Councillor Colin Brewer, Cornwall Council's Heritage Champion said the guidance was a major step forward in taking an "informed, consistent and sensible approach to the future of our unique legacy of chapels" in Cornwall.
"This is not a remote academic issue for those of us, whether Methodist or not, who have grown up with or come to value these chapels as part of our landscape, our shared identity, or our personal histories," he said.
"It means much to us to know that we can work with partners to make sure that these special places will have that same presence in the lives of future generations in Cornwall."