Building Repair Consultants

I have a house which is 50+ years old. Constructed in 15" Laterite stone wall structure .The Roof is steel long pillar ie looks like Railway track line & crossed with wooden multiple structure .Above this tyled( may be earthen coloured sqare tyle) & the roof is covered by thick lime paste.The present status is water lleaking because no maintenance for long period .Now I want to preserve the roof & house without dismantling the roof with RCC.Need your guidance