Building extension over a vaulted roof?

[KittyKK]

Last week, I viewed a great house that has planning permission granted to add a first floor extension (ensuite) on one of the bedrooms.

We’ve seen the architect plans and approvals. Only concern at this stage is that the extension would be over the vaulted roof of the family room below (photo from bedroom window).

Has anyone had experience of doing this type of extension? I will ask the vendor if it is ok for me to call their original architect to ask some practical questions... but it seems a bit more daunting than other extensions we’ve done previously. I’m wondering if the vaulted ceiling below would need to be flattened or if the bathroom would be raised (i.e. up some stairs)...

Interested in any feedback if you’ve considered or been through similar works. Thanks

Wonkylegs will be along in a bit to give you much better advice than I can as a non-expert, but if the ceiling is vaulted as well as the roof, I think you'll have to lose the vaulting and make it flat. I imagine this will involve new joists and a new ceiling below.

Anything is possible at a price, subject to planning permission. Flattening the ceiling would be much more economical, but if you wanted to keep it and have stairs, given the money it would likely be doable.

Yes, it very much sounds like you'd need to remove the existing roof structure down to wallplate level, then construct the first floor extension from there.

It's not dramatically more work than building a first floor extension in place of a conventional roof structure, though - normal ceiling joists are only sized to support the weight of a ceiling, so it would be quite normal even with a conventional roof to remove the whole lot to wallplate level, install stronger joists, and build your extension up from there.

Many thanks all. Appreciate your feedback!

Agree with previous posters that the existing roof structure would be removed, including joists, the existing framework would be strengthened to take the increased load and the new structure would be supported off this enhanced support system.

It makes no economical sense to keep the vaulted roof structure and raise the first floor bathroom.