"Jethro_uk" wrote in message
...
On Sat, 08 Mar 2014 09:48:55 +0000, Brian Gaff wrote:

My roof has none, indeed one can see daylight from inside.
Brian

The roofer who retiled and re-membraned my roof was adamant that it's the
felt that makes it weatherproof, not the tiles ....

Felt is a relatively new thing only used in the last sixty years or so.
We have previously had two thousand years without it.

It makes the roofspace more draught proof and provides a secondary barrier
if there are loose/missing tiles.
During construction, it enables the house to be made weatherproof at an
earlier stage in construction.

It can cause dampness/rot issues if not properly installed too.