Colnmill

Hi, We are currently renovating a house which has been empty for more than 2 years. I have the 5% VAT certificate from the council and all the trades who charge VAT are already only charging me 5% however, I have paid 20% on all materials. My questions are: Can I only put in one claim for this project (it's taking quite a long time)? If so at what point? We created a company to buy the houses, does that company need to be registered with VAT to make the claim, even if we don't think we will hit the VAT earning threshold in the future? How do I make my claim? and how long does it take to process? thanks