Mortgage revaluation during building extension

Keano24

We are building a two storey side and rear extension on our house. We have already put plenty of our own savings into it and have the shell built with all windows, doors, roof, guttering and facia done. We are at a point now where we will have to now save to complete the rest of it, taking it on a room by room basis which we are content with.

Part of our mortgage is up for renewal now and the other option would be to get the house revalued and borrow additional onto the mortgage as it means we can get it done and finished ASAP.

Regardless of expectations of increases in value, is it possible to get a mortgage and revaluation on a house with a half built extension? And if not, at what point and what position would the house need to be in in order for it to be able to get a revaluation and mortgage on it?