In article ,
"keith_765" writes:
Pointing to a tiled valley can course more trouble. Before I comment I
would like to know, which type of tile is on the roof, concrete single lap
interlocking or plain tiles, and is the valley lined with Lead, GRP or
concrete valley trough. By the way 4 to 1 is useless for this type of work.
2 to 1 stiff mix and PVA if you are leaving the old mortar in. BS 5553
states " Open cut lead valley's with plain tiles should not be bedded or
pointed"

Concrete interlocking tiles (similar to Marley Ludlow Plus),
GRP valley trough. The trough has no upstand at the sides
(other than a pair of small ridges) so I suspect it would
overflow easily without forming a mortar gulley. It has a
strip down each side to bond to the mortar.

I've stripped out the old mortar, which had developed a
number of cracks, and come unstuck from some of the tiles.

--
Andrew Gabriel