Hello JP, I am Keith, one of the experts on Just Answer, and pleased to be able to help you with your question.
Here is an extract from VAT Notice 708. You will see that the proposed works would appear to be entitled to the 5% rate:
'Conversion (other than for housing associations) of a non-residential building into a qualifying dwelling or communal residential building and conversions of residential buildings to a different residential use - 5%'
The full notice you can find here and its application can be a tad complex depending upon whether you are the contractor or the customer:
I do hope that my reply has shed some light on the situation, in this case fairly simple.