Architectural conservation provides necessary methodologies and skills to conserve traditional Sri Lankan mural paintings that are user objects in the ancient image houses. Most of these paintings are in dilapidated conditions due to natural decay and human intervention. Reduction of the rate of decay is the most important aspect of their conservation.In this experimental study, we found that methods based on synthetic material that are currently used do not reduce the rate of decay of paintings, only those methods that stabilize the behavior of paintings reduce the rate of decay. It was established that methods based on traditional material could effectively stabilize the behavior of paintings. Based on these findings, appropriate methods of conservation are developed. Prime attention is given to filling, fixation and consolidation. The possibility of using cleaning and reintegration as tools of preservation is discussed.