The fire that damaged part of the roof at the National Library of Wales was started by accident by workers using a blow torch.
An investigation into the cause of the fire has found the device used by workers on the roof caused some wood behind external cladding to ignite.
Two workers were carrying out repairs on the roof at the time, but nobody was injured in the blaze.
More top news
The asphalt was was installed as a sea defence in 1984 to protect 260 homes and businesses.
Public Health Wales has asked people to check in on vulnerable neighbours, family and friends during the cold weather.
A buzzard which was found illegally shot near Powys has prompted concern by the RSPB and police.