Around 12 parked cars and vans were crushed on Wednesday morning when scaffolding on the roof of the Minster Insulation branch in Exeter collapsed.
A 150ft section of scaffolding fell off the roof of the building on the Marsh Barton Trading Estate in Exeter.
No-one was hurt in the incident, although an eight-month pregnant woman was in one of the cars which was hit.
The HSE is investigating the cause of the collapse.
The scaffolding had been due to be taken down in a few days. The scaffolding company have not commented on the incident.
The branch is next door to branches of sister Saint-Gobain merchant brands Graham and Curzon Heating and has been given HSE permission to open again on Friday.
A statement from Minster Insulation said: “We can confirm that scaffolding erected by an independent roofing contractor working at Minster’s Marsh Barton branch has collapsed. No one has been injured although cars in the surrounding area have been damaged.”
Lisa Benbow, head of communications, said: “Thankfully no one was injured in this incident. Police and the emergency services have been called to the branch and the Health & Safety Executive has been informed. An HSE inspector is going to the branch.
“We have also suspended the contractor pending the outcome of our own safety investigation and that of the HSE. We take the issue of customer and employee safety very seriously and will be proactively working with the HSE to help establish the cause of the scaffolding’s collapse.”