Unfortunately due to the number of things you would need to consider as a director before embarking on the project we are unable to give a comprehensive reply.
We assume that you are the homeowner and that the property you live in is not owned by the company but personally by you. As you may be aware the company and the director are completely separate for tax purposes.
You have not indicated if the funds for the proposed conversion are coming from you or from the company. In either case you would not be able to directly offset the costs of the conversion against your company's profit as this is capital expenditure.
There may be other implications and you can find further information here:
Running a business from home
There may also be VAT and Capital Gains implications if the property were to be sold at a later date.
Due to the complexities involved you may wish to seek professional advice.