Raising ground level around existing wooden office building

[JoF]

Hi
I want to build a level paved area against the long side of an existing wooden garden office.
The existing ground against the building is a sloping lawn. The new paved area will be at least 200mm higher than current ground level at the bottom end of the existing slope. My question is how to do this without creating a damp issue inside the building. The building is already sunk into the ground by about 400mm but I don't know what waterproofing may have been done to enable this. I'm not a builder so laymans terms would be helpful.
Thankyou.