Floor tile thickness

[Pete]

I am trying to order our front and back doors but trying to satisfy BR for Part M and maintain a good u-value for our near Passive build is proving difficult. What have people done to meet both standards? Currently we will need a two part sill, one to fit to the concrete floor and butt the floor tiles upto and then a smaller sill that sits on top which will be the door frame. When I have looked at a few manufacturers they have a really small sill that looks really neat and it actually sits on top of the finished floor so in our case tile and then fit the door which does not work for us at all.

So currently we are looking at a Pirnar door which can supply a traditional sloping outer sill which is the only one they do and then the smaller sill on top. RK doors do a similar set up but have a choice of sills for varying situations and this would suit the way we finish off outside. We could pave right upto the door frame with the RK system as it does not have the slope on the lower sill which is our preferred choice but we prefer the Pirnar door to the RK door overall.

If we use a 10mm floor tile on a 10mm adhesive bed what will be the finished thickness, I am thinking about 15mm as I need to be careful to order the the correct door height to achieve the Part M and maintain a decent u-value. (Mods please start another thread if you feel this would be better on it's own)

TIA