Floor cold brigding detail?

[pudding]

Hi all,

 

Little conundrum here regarding our extension, and cold bridging involving a granite post that is under an existing, now internal full height window. The top of the granite is pretty much at the level of where new engineered oak floor boards will go. Options to cover this area I see are:- 

 

1. Drill/grind/cut away at the granite to lower it 50-100mm, then we can put some more PIR sheet and then screed on top before the oak floor.

2. Cut away less, say 20mm of the granite so that the oak floor boards can just fit on top of the granite, maybe with some adhesive foam to fill any small gaps/undulation left from the cutting 

3. Leave the granite as it is, put the oak floor boards up to the edge of the granite in line with the rest of the full length of the wall
(PIR upstands are wonky and not aligned with the full length of the wall due to the random stone wall), and then use a oak cover board on top to fill the gap between the oak floor and the wall, with adhesive foam (so a small amount of insulating material) as in the attached sketch

 

Last solution will be the easiest, but of course would probably have the biggest cold bridge to the ground, but will it really matter much? This granite is now fully internal, so shouldn't get freezing cold in winter. Any comments, or other possible solutions?

 

 

 

 

 

 

 

Cheers.

Edited October 24, 2020 by pudding