FLoating in VR (htc vive chaperone floor 1 foot higher than in game floor)

I found the solution to this:
You need to set the attribute ‘Base Eye Height’ in your VR Pawn to 0.
This fixed it for me.

It is mentioned in this tutorial:
https://docs.unrealengine.com/latest/INT/Platforms/SteamVR/QuickStart/2/

Have a look here:

https://docs.unrealengine.com/latest/images/Platforms/SteamVR/QuickStart/2/Setting_Up_PC_Defaults.jpg