You can apply for a VAT refund on building materials and services if you are:
building a new home
converting a property into a home
building a non-profit communal residence - eg a hospice
building a property for a charity
The building work and materials have to qualify and you must apply to HM Revenue and Customs (HMRC) within 3 months of completing the work.
There is a separate guide to VAT if you are working in the construction industry.