Dave Plowman (News) typed:

In article ,
Mike wrote:
I'd hope not, as it would present a fire path.

I expect both purlins sit side by side on the common wall.

I'll bet it varies area to area with old houses. Don't some terraces
'oop north' have common roof voids? Or was Coronation Street wrong?
;-)

In my first house which was in Battersea, I woke up one Sunday morning to
find water dripping through the bedroom ceiling, went up into the loft to
find the next door neighbours lead pipe leading to their water tank had a
pin hole and was spurting a small water fountain onto my ceiling.

There was only a firewall every 3 houses in that street for some reason, so
down south as well.

--
Mark