Options remain open for Dorset Council's headquarters in Dorchester – including a hotel or flats.

Although councillors have now voted for the conversion of South Walks House to 41 flats the council say a final decision on the building's future will not be made until later in the year.

Property portfolio holder Cllr Tony Ferrari says a range of options have been investigated, confirming that an offer had been made to use the building as a hotel, although the deal on the table was so restrictive that it would have taken the council at least 12 years to get its money back – having to meet the costs of conversion and then discounted the rent for some years.

Cllr Ferrari says that although the flats plan has now been agreed for planning purposes, it remains just one option: "This application isn't a decision to build flats in South Walks House, it is a preparatory step that must be taken to make that conversion possible," he said.

"The decision about what to do with South Walks House is due to be taken in the autumn. The national legislation has changed and this plan needed to be submitted now or it would have been more expensive under the new legislation."

The decision to grant that change of use as 'permitted development' met with opposition from Dorchester councillor Stella Jones.

She told the area planning committee on Tuesday that she could never agree to flats in a building which had nowhere to park buggies or mobility scooters, to dry clothes, of have safe outdoor space for children to play in.

She said the conversion would be expensive to achieve and the purpose-built office block would never be a good home with no outdoor space, or even balconies – and there were no flats proposed which were 'affordable.'

Fellow Dorchester councillor Les Fry said he was also unhappy about the possible conversion and asked if other uses could still be considered – but said that if all other options failed some flats ought to be earmarked for key workers.

The committee was also told that plans have also been made for three commercial units on the Acland Road side of the building which could be used for a range of activities including café, creche, gym, shops, clinic or other 'light' business uses, also without the need for full planning permission.

Cllr Ferrari says the council is keen to get the building, which the last council staff left a month ago, into productive use.

"The council has two objectives that are in conflict with each other. Do something quickly to bring the building back into productive use as soon as possible and at the same time explore all of the possible options to get the best use for the site. You can't look at lots of options quickly…If we don't look at all of them we are faced with criticism for not considering reasonable alternatives," he said.

Cllr Ferrari said the council will not become the developer for the building, suggesting that the best move might be a partnership which would give some control and guard against the building staying empty or being put to an unsuitable use.

He said the council has ruled out doing any conversion work itself as it does not have the expertise to do so.

"This is a council that knows how to get best value for its assets both in simple financial terms but also in terms of their contribution to the regeneration of our towns. We aren't wasting time, we are doing a robust piece of work to ensure we get the best way forward for the building, the people of Dorchester and of Dorset," he said.