Million Pound extension – Lender requiring a structural warranty?

Two years ago I purchased a 4 Bed house for over £450k via a mortgage with Natwest. The house had a large footprint and my plan was the do an extension of the house.

The extension resulted in a new frontage of the house, new outer skin brickwork, reconfiguration of layout, new truss roof..etc. total cost of the extension was about £700k and that’s everything including 2nd and 3rd fixes.

We had planning and independent building regs. Recently during the final stages of the build, my Natwest mortgage was coming to an end, so decided to go with Metro bank, and get some more money out of the property. The valuer came out and said although the property value is about £1.5 million, it’s not suitable for lending as there is no structural warranty in place. A structural warranty is for new builds and this has not been built to a new build standard or specification.

I have planning and building regs for an extension build. Getting a structural warranty policy now will cost over £10k and even then some lenders will not accept a retrospective warranty.

I am a few weeks away from now getting my building regs sign off. How would it be possible to switch to another lender and could NatWest also take the same position if they were also to revalue?

The new build definition in lending criteria states if the property has been built in the last 2 years.

What if I wait 2 years, could I then remortgage?

Kalvinder