Paul Irvine, 44, and Frank Dever, 46, from Paisley, were dismantling the staircase at the former Priory House Hotel in Largs.
Their employer, Paisley firm Ossian Construction Ltd has now been fined £6,000 at Kilmarnock Sheriff Court after an investigation into the incident which left one of the men seriously injured.
On 17 September 2007 the two workers were removing individual stair treads, weighing between 120kg and 150kg, by breaking them up with sledgehammers when the staircase collapsed. The men fell almost four metres to the basement below and were struck by the falling debris.
Mr Irvine was trapped by pieces of the stone treads so large it needed several men to shift them.
Mr Irvine sustained fractures to every one of his ribs and three vertebrae, suffered a punctured lung, and suffered significant crush injuries to his foot and a finger.
Frank Dever suffered bruising and cuts. The events have had a significant traumatic effect on both men.
Ossian Construction Ltd of Glasgow Road, Paisley, pleaded guilty to breaching section 2 of the Health and Safety at Work etc Act 1974 by failing to ensure that there was a safe system of work for the demolition, including a plan for the work, and not providing their employees with the information, instruction, training and supervision they needed to ensure their health and safety.
Following the case, HSE inspector Annette Leppla said: "This was a serious and entirely preventable incident that will affect Mr Irvine in particular for the rest of his life.
"Ossian Construction failed in their duty of care to their employees and both Mr Dever and Mr Irvine are lucky to be alive.
"It's not always obvious how old buildings are put together, and therefore it is particularly important to seek competent advice before any demolition work is undertaken. All employers carrying out working at height must make sure they plan this work properly and give their employees the training and supervision they need to do the work safely."
According to the HSE, falls from height are the biggest single cause of death and serious injury at work. In 2008/9, there were 35 deaths and more than 4,000 major injuries caused by falls from height.