It sounds like your new concrete floor needs an 18mm covering to get it to the same level as the rest of your house..... this is the same thickness as ply.... donuts a problem easily sorted. Either your builder or flooring people need to overboard the concrete

Hi Jonathan, thanks for comment. But they didn’t leave enough space when putting bifolds in- there is only 25mm between concrete and bifold. So if 18mm of that is covering we only then have 7m for flooring- which isn’t enough for our plan for Quickstep. So now I’m frantically looking for thin flooring option but also just annoying that we have limited options and cannot have the flooring we wanted throughout the ground floor. Does it sound like builder mistake? Not sure why they wouldn’t have matched it level or left room for flooring company to do so. Thx

Consider LVT instead of your planned floating floor

Same problem apparently. Thank you though!

When we done our renovation, the doors company came out and between the door company and the builder they made an agreement on where the level would be to allow our chosen flooring to get put down. We told them what flooring we picked and the height requirements for that. Based on that, the size of doors was calculated and height at which they would start at. It sounds as if that wasn't done. Did you tell the builder what flooring you were having and the heights it needed and was this all set out before the doors went in?

Well the bifold that has been fitted is now a fixed point/level and so that is what your governed by along with the concrete, so your solution will have to be with the floor boards i’m guessing. Could you lift Your floor boards and noggin in between the floor joists, then inlay floorboard between the joists bringing the level down to the finished concrete level.