And while he is looking forward to spending more time fishing he remains passionate about his craft.
Mr Muir joined the Historic Scotland's predecessor body, the Ministry of Works, as a qualified mason at the age of 26 in 1971.
Since then he worked his way up the career ladder to become a works manager looking after repairs and maintenance for 28 sites from castles and abbeys to stone circles in a wide area round his home town of Stranraer.
It is very much thanks to his efforts, and those of his colleagues, places like Threave Castle are the superb attractions they are today.
Peter Spencer, Historic Scotland regional works manager, paid tribute to Mr Muir as a superb craftsman and excellent manager.
"He's very much of the old school, every job he's responsible for is done to the highest possible standards. His own workmanship was excellent and he runs his squad in an exemplary manner.
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"Norman is a very conscientious and determined person who is well-respected by all those who work with him and across Historic Scotland. Thanks to him some of our most precious historic monuments remain in superb condition and are enjoyed by visitors from all over the world."
Mr Muir, aged 65, who runs the depot based at Glenluce Abbey was part of the team which entirely refurbished Castle of Park, which then passed to the Landmark Trust.
But his favourite sites are Rowallan Old Castle and MacLellan's Castle.
"I've worked at both of them and they are lovely places with so much history to them - and in both cases the work was very interesting," he said.
Such was Mr Muir's reputation for excellence that he was awarded an MBE for services to Scotland’s heritage in the 1999 New Year's Honours.
While modest about his own achievements he is a keen advocate of stonemasonry.
He said: "I've been lucky, I have such a good squad, they never need telling twice that something needs to be done.
"I'm looking forward to retiring, and spending some more time fishing, but I'd recommend stonemasonry to any young person today. They say it's a dying trade but it needn't be, in fact there should be more people being trained as there's so much work out there which needs doing.
"It makes an excellent career, because it’s so skilled and the work is so satisfying."
Retirement will also give Mr Muir the chance to spend more time in his home in Stranraer which, characteristically, he built himself around six years ago.
(GK/JM)
