The potentially lethal fibres were disturbed by unqualified workmen and left spread around the premises for three weeks.
In a prosecution by the Health & Safety Executive (HSE), Cardiff Magistrates heard that Timberwise (UK) Ltd, a national company specialising in damp and timber repairs, committed four offences and was fined a total of £18,000 and ordered to pay £5,314 in costs.
The court was told that Timberwise was contracted to carry out the work in an antiques shop at in High Street, Cowbridge in the Vale of Glamorgan in July, 2011.
Timberwise sent employees to work on the site to survey and strip out parts of the building affected by damp and wood rot.
No check was made for the presence of asbestos. None of the workers had received sufficient information, instruction or training in asbestos awareness or removal and Timberwise did not have a license to remove or handle asbestos containing materials.
Asbestos insulation boards were removed in a back room by one of the workers and the ceiling was demolished. The uncontrolled removal of the asbestos boards and demolition work caused the disturbance and spread of potentially deadly asbestos fibres.
Instead of arranging for the proper disposal of the asbestos, the dust was swept into rubble bags and dumped in a skip lorry, along with the asbestos insulation boards. The asbestos material was immediately identified at the waste transfer site and were collected by Timberwise and left in the backyard of the shop.
The owners of the building contacted the HSE and then arranged for a licensed removal company to undertake a full environmental clean of the building.
HSE inspector Steve Richardson said after the hearing: "This incident was entirely preventable and would not have happened if Timberwise had provided adequate information, instruction and training to its staff.
"The company had no procedures to check for the presence of asbestos and as a result, has put the health of its workers and the shopowners at risk of potentially fatal asbestos-related lung diseases."
Timberwise (UK) Ltd, of Drake Mews, Gadbrook Park, Rudheath, Cheshire, pleaded guilty to four offences under the Control of Asbestos Regulations 2006 and was fined the following amounts: