More than 35 firefighters tackled the blaze at Grade II listed Newell House in Sherborne in April.
Cornhill was closed while work was carried out to make the building safe following the fire.
Cornhill Road will stay closed until the former school, left a charred shell, is made safe.
The three companies has paid out a total of £33,500 after the Environment Agency's investigations.
The blaze at the three-storey former independent school Newell House caused the roof to collapse.
Dorset councillor for Sherborne, Robin Legg, says the site was on the council's radar.
Firefighters have spent the night tackling a blaze at the three‑storey building.
One resident said the changes will mean she has drive further, causing her more pain.
The Hawkstone Farmers' Choir were rewarded by judge Amanda Holden for their performance.
