ben asks:
If there is a space from the dead one till the gollel why is someone tameh if he is mahil over it it should be a tefach chotzetz
ben, jerusalem
The Kollel replies:
An item which becomes a Golel receives Tum'ah of its own (Chulin 72a; Rambam, Hilchos Tum'as Mes 2:15).
Also, you're talking about a dead body in a room and the Din of above the room (Tefach Chotzetz). In this case there is a grave which is Tamei from all sides. See Rambam ibid.
All the best,
Reuven Weiner