the gemara in brochos daf 19b says a tefach of separation prevents the tumah from going up but the gemara in nazir 53b bottom line says if there is a tefach separation even the sides of the coffin the tumah goes straight up and is metamei ?
yehoshua, ny
You are correct to say that here the Tumah goes up even if there is a Tefach above the Tumah, and that the Tumah goes up across the whole of the Kever. This is because here we are discussing a new Tumah called Kever Sasum, a closed grave. Here the m'Tamei is in fact the Kever, not the dead body inside the Kever. If there is an opening to the Kever, then the Din is as you quote from the Gemara in Berochos, that the Tumah only goes up above the Meis, and only if there is no gap of a Tefach above the Meis.
Dov Freedman