The roof of the building on Main Road in Otterbourne, near Eastleigh, collapsed during the blaze, which broke out at about 03:30 GMT.
No injuries were reported at the site, which also contains workshops and offices. An investigation is under way.
The neighbouring convenience store, which was saved, is due to reopen later.
Ty Whitlock, commanding officer at the scene, said: "When we pulled up we were faced with flames coming out of the roof, coming out of the glass doors and windows and obviously huge amounts of smoke coming from the eaves."

The artist and photographer David Gwinnutt was part of the 1980s art scene that centred around the Blitz club in London's Covent Garden, leading to the creatives who frequented it being dubbed the "Blitz kids".
Although they were known for their flamboyant makeup and performances, Gwinnutt captured these young men and women relaxing around their homes, which were often squats or rented council houses.
Against a backdrop of the economic recession and unemployment of the early 1980s, some of these club-goers went on to become established artists and film-makers in their own right.
"Derek Jarman [the experimental British filmmaker] really liked the photographs I had taken of him and asked me who I'd most like to photograph. I said David Bowie," Gwinnutt remembered about this photograph.
"He laughed and said I should photograph John Maybury."
Maybury was also a film-maker, who used theatrical themes and visuals in his work.
The portrait above was taken as he smoked his first cigarette of the day in his Camden flat.
Gilbert & George are artists who have spent their lives as "living sculptures", wearing sharp suits and making their entire existence a performance, down to claiming to eat in the same Turkish restaurant every evening.
Gwinnutt met them at Planets nightclub in Piccadilly and, noticing how they stood out from the crowd in their neat suits, asked to photograph them in their East London home.
The artist Cerith Wyn Evans stands on the set of his film Epiphany, which took inspiration from the London club scene and starred friends such as the flamboyant performance artist Leigh Bowery.
In the image below, the artist Maggi Hambling looks in the mirror while smoking at a sink.
She is best known for her sculpture on Aldeburgh beach dedicated to Benjamin Britten, as well as another sculptural "conversation" with Oscar Wilde, located near Trafalgar Square.
In this photograph (above), co-founder of the fashion label BodyMap, David Holah, reclines on a sofa during a dinner party in Bloomsbury.
At the time of this photograph below, Norman Rosenthal was the Exhibitions Secretary of the Royal Academy in London.
Sensation, an exhibition he curated for the Academy in 1997, featured the work of Cerith Wyn Evans amongst others.
The picture was taken in Rosenthal's flat opposite the Academy, which was so sparsely furnished the curator and art historian was forced to sit on the floor.
Although Rosenthal was reclining, Gwinnutt recalled, "I felt all the time that he was observing me."
The film producer Alison Owen, mother of singer Lily Allen, stands in a doorway in the mid 1980s.
Since this was taken, she has worked on films such as Shaun of the Dead, The Other Boleyn Girl and Brick Lane.
Although known for his flamboyant dress sense and immaculate makeup, fashion designer Stephen Linard is seen below in bed in his Kings Cross flat.
On graduating from St Martin's School of Art, his first catwalk show of "mean and moody menswear" propelled him to overnight success.
The man at the centre of this artistic scene, Derek Jarman [below] stares intensely down the camera lens while his protégé John Maybury stands behind him.
"Using only his handheld camera and natural light, Gwinnutt's grainy black and white photographs feel unguarded and spontaneous," said curator Sabina Jaskot-Gill of the National Portrait Gallery, "offering a glimpse into the private worlds of these rising stars who lived, worked and played together".
"Gwinnutt's photographs serve as a social document of a moment that had far-reaching effects on the cultural landscape."
Up to 40 firefighters have been tackling a large fire which destroyed a garage in Hampshire.
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David Gwinnutt: Before We Were Men runs at the National Portrait Gallery from 16 March-24 September 2017.