Hello, I am Keith, one of the experts on Just Answer, and happy to help you with your question.
Have a look here for VAT Notice 708 which covers this matter. Such a conversion is subject to VAT at 5% and your client has to advise his builder that it is the appropriate rate.
As his business has ceased he cannot reclaim this input tax so it is essential that the contractor he employs uses the reduced 5% rate otherwise he will be out of pocket
I do hope that you find my reply of assistance..
he is managing the build. its more to do with the vat claim on materials that he has bought
He has no claim as his business has ceased. Sorry to rain on your parade.